Cẩm Nang Điều Trị Chỉnh Hình Hàm Mặt (Tiếp Cận Đa Chuyên Khoa)

38
Handbook of Orthognathic Treatment
Figure 2.26  Screen capture from iCATvisionTM showing the intimate relationship between the ID nerve and the
unerupted LR8 in a patient scheduled for bilateral sagittal split osteotomy.

Dentofacial assessment
39
• Monitoring of jaw growth and occlusal change
prior to surgery.
• Monitoring of orthodontic treatment progress.
• Surgical profile prediction planning (see Chapter 6).
• Assessment of surgical change.
• Monitoring of skeletal and occlusal relapse.
It must be remembered that a cephalogram is a two-
dimensional representation of a three-dimensional
object that has several bilateral structures. That said,
for patients without significant asymmetries, lateral
cephalometry remains a useful tool, which is a rou­
tine part of orthognathic patient management for
most clinical teams. It cannot be over-emphasised,
though, that cephalometric findings should always be
interpreted against the background of an adequate
clinical assessment and are only an adjunct to clinical
judgement, rather than a stand-alone definitive
assessment. There are a number of ways in which
lateral cephalograms can be analysed in order to fulfil
the applications listed above.
2.6.1  Gross inspection
An experienced clinician can derive a good deal of
information regarding a patient’s dentofacial dys­
morphology simply by viewing the image, without
the aid of any objective analysis. A general impres­
sion of the size and shape of the jaws, the approxi­
mate incisor inclinations and dento-alveolar heights,
as well as the form and thickness of the soft tissues
can be gained, at a glance.
Certain anatomical features do not lend themselves
easily to measurement, but are none-the-less impor­
tant to assess, such as the morphology of the mandi­
ble, which in patients with extreme vertical dysplasias,
will exhibit the characteristic features of a growth
rotation. For example, it can quickly be seen in Figure
2.27a that:
there will have been adequate resolution of soft
tissue swelling, but the position of the surgical seg­
ments may reflect a degree of early relapse in some
cases. As a compromise, we consider this to be the
optimal time to capture both hard and soft tissues
simultaneously, whilst minimising exposure to ion­
ising radiation.
The three-dimensional position and orientation of
the condylar segments, in sagittal split osteotomy
cases, can be assessed using CBCT. The presence of
condylar torqueing can be evaluated and addressed
as deemed appropriate.
The position of plates and screws, and their prox­
imity to anatomical structures, can be identified on
a post-operative scan.
Lateral cephalogram
See Section 2.6.
PA skull radiograph
This view can also be classed as a cephalogram, in
that it is standardised and can be analysed using
linear and angular variables. It is commonly used to
assess facial asymmetries, but lacks the 3D informa­
tion that a CBCT scan is now able to provide. In the
authors’ clinical practice, the PA skull view has now
been entirely replaced by the CBCT scan.
2.6  Cephalometrics for orthognathic
patients
Lateral cephalograms have the following applications
in the management of orthognathic patients:
• Assessment
and
diagnosis
of
dento-skeletal
dysmorphology.
Figure 2.27  Lateral cephalograms of
patients showing the typical features
of (a) short-face syndrome and (b)
long-face syndrome.
a)
b)

40
Handbook of Orthognathic Treatment
2.6.3  Quantitative analysis
Numerous cephalometric variables and analyses have
been developed, with the aim of measuring different
aspects of the dentofacial complex. The values
obtained quantify how the patient’s face varies from
average, based on published ‘normal’ values. However,
it is important to remember that the population from
which the reference values are derived may differ
from the patient’s own local population, even within
the same racial group. Standard racial values should
be referred to, wherever they are available. Quantita­
tive analysis can also be used to monitor antero-
posterior and vertical change in the dentofacial
complex.
The clinician must be aware of the limitations
of cephalometry with regard to the accuracy and
• The lower mandibular border is flat or rounded.
• The gonial angle is rounded with little ante-gonial
notching.
• The course of the ID nerve is curved.
• The condyle is angled forwards.
• The ramus height is increased.
• The mandibular symphysis is upright with accom­
panying progenia.
• The lower molars have a forward path of
eruption.
• The anterior vertical dimensions are reduced.
These are the classic cephalometric features of
short-face syndrome and are only fully appreciated
on gross visual inspection.
The cephalogram shown in Figure 2.27b shows all
of the converse features associated with long-face
syndrome and it can be readily seen how dramati­
cally different the two images are in their overall
vertical proportions.
In addition, the clinician should be alert to signs
of possible pathology of the base of the skull, such as
enlargement of the Sella Turcica in an acromegaly
patient, which should be picked up early on initial
inspection.
2.6.2  Qualitative analysis
The use of average templates derived from normal
populations, such as the Bolton templates, allows for
quick confirmation of the key areas of dysmorphol­
ogy (Figure 2.28). There are potential problems with
superimposing the tracings on the SN line, if the
patient’s cranial base differs from average and also
with the scaling of the templates, which will not
always be accurately matched to the patient.
Drawing the key horizontal reference planes on a
cephalogram, allows better visual appreciation of the
patient’s vertical skeletal relationships, with the posi­
tion of the convergence point indicating any varia­
tion from normal (Figure 2.29).
Figure 2.28  Lateral cephalogram of a class III patient
(red) superimposed on a Bolton normal template (blue),
using the S-N line as the reference, holding at Sella. It is
immediately apparent that the patient has a mild degree
of maxillary deficiency, a greater degree of mandibular
prognathism and an increased lower anterior face height.
Figure 2.29  Drawing the horizontal
reference planes (after Sassouni) helps
the clinician to assess vertical
dysmorphology on the lateral
cephalograms of a short-faced patient
(a) and long-faced patient (b).
a)
b)

Dentofacial assessment
41
Table 2.3a  Hard tissue cephalometric landmarks
Landmark
Definition
S
Sella: the centre of the sella turcica, determined by inspection.
N
Nasion: the most anterior point of the frontonasal suture.
Or
Orbitale: the lowest point on the infraorbital margin.*
Po
Porion: the uppermost point on the outline of the bony external auditory meatus.*
Ar
Articulare: the point of intersection between the outlines of the posterior cranial base and the dorsal
condyle.*
ANS
Anterior nasal spine: the tip of the anterior nasal spine.
PNS
Posterior nasal spine: the tip of the palatine bone in the hard palate.
A
Point A (subspinale): the deepest point on the anterior outline of the maxilla below ANS.
B
Point B (supramentale): the deepest point on the anterior bony outline of the mandibular symphysis.
Uia
Upper central incisor apex: the apex of the root of the most prominent upper central incisor.
Uie
Upper central incisor edge: the tip of the crown of the most prominent upper central incisor.
Lie
Lower incisor edge: the tip of the crown of the most prominent lower central incisor.
Lia
Lower incisor apex: the apex of the root of the most prominent lower central incisor.
UM
Upper molar cusp: the tip of the mesiobuccal cusp of the upper first molar.*
LM
Lower molar cusp: the tip of the mesiobuccal cusp of the lower first molar.*
Pg
Pogonion: the most anterior point on the outline of mandibular symphysis below B point.
Me
Menton: the lowest point on the outline of the mandibular symphysis.
Go
Gonion: the most inferior and posterior point on the outline of the gonial angle of the mandible.
Constructed point, found by bisecting the angle formed by tangents to the posterior and inferior borders
of the mandible.*
*Bilateral structures may project a double image on the cephalogram, with two identifiable landmarks. In such cases the
convention is to use a point midway between the two.
reliability of the landmarks and measurements. The
values obtained from any analysis must be inter­
preted with caution and only as an adjunct to a
thorough clinical assessment. As a general rule, it is
unwise to fully trust any single variable or analysis
and it helps to measure the same feature using two
or more contrasting variables, particularly where the
figures obtained are surprising or at odds with the
clinical impression.
Tables 2.3a and 2.3b list a number of basic land­
marks and reference lines, along with their defini­
tions. Tables 2.4a, 2.4b, and 2.4c list some of the
more commonly used variables, along with their
values and some notes of caution regarding their
application. These are also illustrated in Figure 2.30.
Antero-posterior jaw relationship
The antero-posterior position of the maxilla and
mandible, and their relationship to each other, are
commonly measured in relation to the SN line, which
represents the anterior cranial base (Figure 2.30a). For
SNA and SNB, values above or below their normal
range will tend to indicate prognathism or retrogna­
thism of the maxilla or mandible, respectively.
However, for the angles SNA, SNB and ANB to be
reliable, the SN line must be angled normally. If
Table 2.3b  Cephalometric reference lines
Line
Definition
SN
SN line: Line through Sella and Nasion. Represents the anterior cranial base.
FP
Frankfort Plane: Line through Porion and Orbitale. Also termed “Frankfort horizontal”.
Max
Maxillary Plane: Line through PNS and ANS.
FOP
Functional Occlusal Plane: Line through the tips of cusps of the lower first molars and premolars.
Mand
Mandibular Plane: Line through Go and Me.

42
Handbook of Orthognathic Treatment
Table 2.4a  Antero-posterior jaw relationship
Variable
Type
Description
Value(s)
Potential problems
SNA
(Angle between
lines SN and
NA)
Angular
Relates the maxilla
to the anterior
cranial base in the
A-P plane.
81 ± 3°
Prone to unreliability
due to variation in
the angle of the SN
line and the A-P
position of Nasion.
A-point can
sometimes be
difficult to locate.
SNB
(Angle between
lines SN and
NB)
Angular
Relates the mandible
to the anterior
cranial base in the
A-P plane.
78 ± 3°
Relies on the SN line
and N-point, as for
SNA.
ANB
(Angle between
the lines AN
and NB)
Angular
Relates the maxilla
to the mandible
in the A-P plane
with reference to
N point.
3 ± 2°
Prone to error due to
variation in the
angle of the SN line
and the SNA angle.
The Eastman
correction can be
applied to
compensate for an
SNA value out with
its normal range, but
only if the SN-Max
angle is normal (8°
+/- 3°).
BO-AO
(Relative positions
of B-point and
A-point along
the FOP)
Linear
(Wit’s
appraisal)
Relates the maxilla
to the mandible
parallel to the
Functional
Occlusal Plane
using
perpendicular
lines from A and B
point.
Females: 0 ± 1.8 mm
Males: 1 ± 1.9 mm
(i.e. in males BO
meets the
FOP 1 mm ahead of
AO)
Very dependent on the
inclination of the
FOP, which can be
greatly affected by
the curve of Spee.
Variation in the
occlusal plane
directly affects the
relative positions of
A and B points.
A-N
perpendicular
Linear
Relates the maxilla
to a line dropped
perpendicular to
the Frankfort
Plane from
Nasion.
Females:
0.4 ± 2.3 mm
Males: 1.1 ± 2.7 mm
Measurements to both
A and Pg are very
sensitive to any
variation in the
orientation of the
Frankfort Plane, since
this directly affects
the position of N
perpendicular.
Pg-N
perpendicular
Linear
Relates the mandible
to a line dropped
perpendicular to
the Frankfort
Plane from
Nasion.
Females:
−1.8 ± 4.5 mm
Males: −0.3 ± 3.8 mm

Dentofacial assessment
43
Table 2.4b  Vertical jaw relationship
Variable/analysis
Type
Description
Value(s)
Potential problems
FMPA
(Frankfort-
mandibular
planes angle)
Angular
Relates the inclination of the
mandibular plane to the Frankfort
Plane.
27 ± 4°
Relies on the Frankfort
Plane as a horizontal
reference. Anatomic
Porion can be difficult
to identify.
MMA
(Maxillary-
mandibular
planes angle)
Angular
Relates the inclination of the
mandibular plane to the maxillary
plane.
24 ± 4°
Relies on the maxillary
plane as a horizontal
reference, which can be
tipped backwards or
forwards.
SN-Max
(SN- maxillary
plane angle)
Angular
Relates the SN line to the maxillary
plane. Measured prior to carrying
out the Eastman correction to
confirm that the angle of the SN line
is normal, (Figure 2.31).
8 ± 3°
Can be unreliable if the
angle of the maxillary
plane is abnormal (see
Figure 2.2.).
UAFH
(Upper anterior
face height)
Linear
The distance between Nasion and ANS
measured perpendicular to the
Frankfort Plane (or true horizontal).
55 ± 8 mm
Both measurements may
vary with any error in
the angle of the
Frankfort plane as well
as with any tip of the
maxillary plane.
LAFH
(Lower anterior
face height)
Linear
The distance between ANS and
Menton measured perpendicular to
the Frankfort Plane (or true
horizontal).
68 ± 8 mm
TAFH
(Total anterior face
height)
Linear
The sum of UAFH and LAFH.
124 ± 8 mm
LAFH percentage
(Lower anterior
face height
percentage)
Proportional
The ratio of LAFH to TAFH expressed as
a percentage. Intended to show any
disproportion between the lower and
total anterior face heights.
55 ± 2%
UPFH
(Upper posterior
face height)
Linear
The distance between Sella and PNS
measured perpendicular to the
maxillary plane.
45 ± 5 mm
LPFH
(Lower posterior
face height)
Linear
The distance between PNS and Gonion
measured perpendicular to the
maxillary plane.
34 ± 5 mm
TPFH
(Total posterior
face height)
Linear
The sum of UPFH and LPFH.
79 ± 6 mm
LPFH percentage
(Lower posterior
face height
percentage)
Proportional
The ratio of LPFH to TPFH expressed as
a percentage. Intended to show any
disproportion between the lower and
total posterior face heights.
44 ± 1%
Ar-Go
(Mandibular ramus
length)
Linear
The distance between Articulare and
Gonion.
Females:
55.6 mm
Males:
62.0 mm
Ramus length should
ideally be measured to
Condylion but this point
is difficult to identify
and Articulare is
probably more reliable.
Ar-Go-Me
(Gonial angle,
between lines
Ar-Go and
Go-Me)
Angular
The angle between the posterior
border of the ramus and the lower
border of the body of the mandible.
128 ± 7°

44
Handbook of Orthognathic Treatment
Figure 2.30  (see also Tables 2.4a-c) (a) Angular cephalometric variables, describing the horizontal and vertical jaw
relationship. (b) Linear and proportional variables, describing the vertical facial dimensions.




N
S
Po
ANS
PNS
Or
Go
Me

FP
Ar
UM
LM
Uie
Lie
N
S
Po
A
B
ANS
PNS
Or
Uie
Lie
Uia
Lia
Ar
Go
Me
FP
a)
b)
=
=
=
=
=
Table 2.4c  Dento-alveolar dimensions
Variable
Type and
origin
Description
Value(s)
Potential problems
Ui-Max (or Ui-FP)
(Upper incisor to
maxillary or
Frankfort plane
angle)
Angular
The angle between the long axis of
the upper central incisor and the
maxillary plane or Frankfort plane.
109 ± 6°
Upper incisor apex
can be difficult to
locate. Maxillary
plane may not be
horizontal.
Li-Mand (Lower
incisor to
mandibular plane
angle)
Angular
The angle between the long axis of
the lower central incisor and the
mandibular plane.
92 ± 6°
Lower incisor apex
is particularly
difficult to locate.
Ui-Li Inter-incisal
angle
Angular
The angle between the long axes of
the upper and lower incisors.
130 ± 6°
As above.
UADH (Upper
anterior dental-
alveolar height)
Linear
The distance between the upper
central incisor edge and the
maxillary plane, measured
perpendicular to the maxillary plane.
33 ± 3 mm
LADH (Lower
anterior dento-
alveolar height)
Linear
The distance between the lower
central incisor edge and menton,
measured perpendicular to the
maxillary plane.
Females: 40 ± 2 mm
Males: 44 ± 2 mm
Will vary with the
way in which the
mandibular plane
is constructed.
UPDH (Upper
posterior
dento-alveolar
height)
Linear
The distance between the upper first
molar mesial cusp and the maxillary
plane, measured perpendicular to
the maxillary plane.
28 ± 3 mm
LPDH (Lower
posterior
dento-alveolar
height)
Linear
The distance between the lower first
molar cusp and the mandibular
plane, measured perpendicular to
the mandibular plane.
38 ± 3 mm
Will vary with
tipping of the
maxillary plane.

Dentofacial assessment
45
Figure 2.31  (a) Lateral cephalogram of a patient with clinical maxillary deficiency. The SNA angle is deceptively large,
due to a flat anterior cranial base (S-N line). (b) The maxillary position relative to the Nasion perpendicular line
(McNamara analysis) is more in keeping with the clinical impression (A-point 5.0 mm behind).
Po
Or
S
N
ANS
PNS
A
84
FP
Po
N
Or
Pg
A
5.0
0.0
FP
a)
b)
either Sella or Nasion is significantly out of position,
or the jaws are bi-maxillary protrusive or retrusive,
this will affect the values obtained. In orthognathic
patients, this is often the case and the clinician
should be aware of the potential problems that can
be encountered.
The unreliability of SNA.  Figure 2.31a shows the
cephalogram of a patient, who had clinical signs of
antero-posterior maxillary deficiency. A reduced SNA
value would have been anticipated, but in this case
it is increased. The clinician would clearly be mis­
guided to accept this figure as an indication of maxil­
lary prognathism, since it can be explained by the
flatness of the anterior cranial base (SN line) along
with an SN-Max angle below the normal range.
When the McNamara analysis is applied, which relies
on the Frankfort Plane, a value more in keeping with
the clinical impression is obtained (Figure 2.31b).
The Eastman correction.  Where the SNA angle is
outside its normal range, this can result in a change
in the ANB angle, which is not a true reflection of
the jaw relationship. The Eastman correction is
intended to compensate for this and is illustrated in
Figure 2.32.
Whilst the Eastman correction is valuable in many
cases, the clinician must be aware of its limitations.
A scenario is illustrated in Figure 2.33 in which a class
II patient has an SNA value of 85° and an ANB value
of 8°, which is consistent with the clinical impres­
sion. If the Eastman correction was to be applied,
ANB would be reduced to 5°, which would indicate
only a mild class II skeletal jaw relationship and
would be misleading. However, the value of the
SN-Max angle is outwith its normal range of 8 +/- 3°
due to the flatness of the SN line, so the correction
is contra-indicated (see also Figure 2.32c).
The effect of the vertical dimension on ANB.  Pa­
tients with increased vertical proportions can present
a problem when using the cranial base as a reference,
since their mandibular and occlusal planes are usu­
ally rotated downwards and backwards, thus increas­
ing or reducing the ANB angle, in class II and III cases
respectively. For the high angle patient in Figure
2.34a, ANB is surprisingly large, given the clinical
impression of a significant class III jaw discrepancy.
Applying the ‘Wits’ appraisal removes the cranial
base as a reference and measures the jaw relationship
parallel to the occlusal plane (see Table 2.4a), yielding
a result more in keeping with the clinical picture
(Figure 2.34b).
Vertical skeletal dimensions
Mandibular plane angle.  The vertical jaw rela­
tionship is described by a combination of angular,
linear and proportional variables (Figure 2.30), which
are aimed at describing a patient’s vertical facial type
(normal, long or short) and the growth pattern and
morphology of their mandible (normal, backward or
forward). The inclination of the lower border of the
mandible is described by both the FMPA and MMA.
Values above and below the normal range will be

46
Handbook of Orthognathic Treatment
reliability and look for the cause of any unexpected
values.
Face height proportions.  The linear and propor­
tional variables describe the effect of the growth
pattern of the mandible on the heights of the ante­
expected to accompany a backward or forward man­
dibular growth rotation respectively. However, the
Frankfort and maxillary planes are not always parallel
and the maxillary plane is particularly prone to vari­
ation in orthognathic patients. It is therefore advis­
able to measure both angles together for increased
Figure 2.32  The Eastman correction explained: (a) When the SNA angle is within normal limits (81 +/− 3°) and the
angle of the S-N line is normal, the ANB angle will accurately reflect the antero-posterior jaw relationship. (b) If Nasion is
positioned too far forward or back relative to the jaws, the ANB angle will change and become inaccurate. To
compensate for this, subtract 0.5° from ANB for every 1.0° of increase in SNA, and vice versa. (c) The Eastman correction
should only be carried out if the SN-Max angle is within normal limits (8 +/− 3°) because, if the angle of the S-N line is
too steep or too shallow, this alters the SNA angle without any corresponding change in the ANB angle.
c)
S
N
PNS
ANS
A
B
N**
N*
Po
Or
84
90
72
71
-1
6
FP
a)
b)
S
N
PNS
ANS
A
B
Po
Or
88
85
8
3
S*
FP
S
N
PNS
ANS
A
B
Po
Or
81
78
8
3
FP

Dentofacial assessment
47
Figure 2.33  In this class II patient, the Eastman correction
is contra-indicated due the value of the SN-Max angle
lying outwith its normal range.
Figure 2.34  (a) In this class III case with a high FMPA the ANB angle is only slightly reduced. (b) The “Wits” appraisal
gives a value of −12 mm between BO and AO, measured along the Functional Occlusal Plane (FOP).
8
82 83
-1.0
Po
N
Or
A
B
S
PNS
ANS
FP
34
Po
Or
A
B
FP
FOP
a)
b)
12.0
Dento-alveolar dimensions
Incisor inclinations.  Cephalometric analysis is
helpful in confirming the inclinations of the incisors,
particularly where they appear compensated clini­
cally. Figure 2.36a shows the tracing of a class III case,
which confirms that the upper incisors are proclined
and the lowers retroclined beyond their normal
ranges, as expected. The tracing in Figure 2.36b con­
firms that the lower incisors are proclined in compen­
sation for the class II skeletal pattern, but the upper
incisors are also markedly proclined due to the pres­
ence of a lower lip trap. In the class II, division 2
patient in Figure 2.36c, the upper incisors are con­
firmed as being severely retroclined, under the action
of the upper lip and the lowers are mildly retroclined.
Upper incisor inclination is commonly measured
relative to the maxillary plane, but this is not always
reliable in orthognathic patients, particularly those
with vertical dysplasias where it is often tipped for­
wards or backwards. It may also be altered through
maxillary surgery. It is therefore also advisable to
measure the upper incisor inclination relative to the
Frankfort Plane (or true horizontal), since this remains
constant throughout treatment and may be more
relevant in assessing the inclination of the incisors
from an aesthetic standpoint.
Lower incisor inclination and the mandibular
plane.  There is a school of thought that the assess­
ment of lower incisor inclination should take account
of the FMPA, since a mandibular growth rotation will
rior and posterior facial skeleton. A patient with a
short face will be expected to show reduced ratios of
LAFH:TAFH and LAFH:LPFH (Figure 2.35a), while the
opposite will be the case in a long-faced patient
(Figure 2.35b).

Figure 2.35  (a) In short-faced patients, the lower anterior face height (LAFH) is reduced and the lower posterior face height
(LPFH) is increased, reflecting a forward mandibular growth rotation. The converse is true for long-faced patients (b).
N
S
Po
ANS
PNS
Or
Go
Me
FP
49%
51%
N
S
Po
ANS
PNS
Or
Go
Me
FP
59%
41%
a)
b)
Figure 2.36  Cephalometric diagrams illustrating incisor compensations in the main malocclusion types. It is useful to
measure the upper incisor inclinations to the Frankfort horizontal as well as the maxillary plane: (a) Class III, with
retroclined lowers and proclined uppers. (b) Class II, division 1, with a lower lip trap and bi-maxillary proclination. (c)
Class II, division 2, with bi-maxillary retroclination.
125
71
FP
122
121
109
FP
123
84
87
FP
81
a)
b)
c)

Dentofacial assessment
49
Where idiopathic condylar resorption is suspected
as the cause of progressive anterior open bite, super­
impositions will reveal decreasing ramus height.
Assessment of treatment change
Cephalograms can also be used to assess the dental
changes produced by pre-surgical orthodontics and
the skeletal changes produced by surgery. Because
orthognathic patients are usually adults who have
stopped growing, the SN line can be used reliably as
the reference plane for superimpositions, such that
any changes observed are entirely the result of move­
ment of the dentofacial components.
Assessment of relapse
It is not our routine to take an immediate post-
operative cephalogram because a second CBCT scan
is taken six months after surgery for every patient in
order to allow assessment of surgical change in three
dimensions as required. It is usually at the two-year
post-operative review appointment that the first
conventional cephalogram is taken. If any signs of
relapse are seen clinically a superimposition can be
carried out of this image onto a cephalometric view
derived from the CBCT data. Relapse can be due to
skeletal and/or dentoalveolar changes and cephalom­
etric superimposition allows this to be analysed and
quantified, at least in the antero-posterior and verti­
cal planes. Subsequent follow-up cephalograms are
taken annually, up to five years post-operatively.
2.7  Special investigations
There are some progressive conditions that require
additional special investigations for adequate assess­
ment and diagnosis. The most common of these are:
tend to alter the inclination of the lower incisors
within their soft tissue envelope. Hence, if the FMPA
is 5° greater than average, the inclination of the lower
incisors would be expected to be 5° less than average
and visa versa, such that the FMPA and lower incisor
inclination values add up to 120°. This can have
implications for the planning of pre-surgical ortho­
dontics (see Chapters 3 and 4).
Dento-alveolar heights.  The heights of the poste­
rior dento-alveolar processes tend to reflect the man­
dibular growth pattern. In a short-faced patient with
a deep overbite, the posterior dento-alveolar heights
are usually reduced (Figure 2.35a), while in a patient
with a long facial type and a skeletal open bite they
are usually increased in (Figure 2.35b).
The relationship between the anterior dento-
alveolar heights and the mandibular growth pattern
is not so straightforward because the extent of incisor
eruption is determined by a combination of their
inclinations and occlusal relationship, and the action
of the lips and tongue. For example, in a class III
case with vertical maxillary deficiency, the upper
dento-alveolar height will invariably be reduced, but
in a class II, division 2 case, with an increased inter-
incisal angle, the upper incisors are free to over-erupt.
Conversely, in a high angle case with anterior open
bite, the upper anterior dental height would usually
be increased, but it may be reduced if a long-standing
digit sucking habit has impeded vertical dento-
alveolar development.
In summary, it is essential to appreciate that cepha­
lometric findings are only a guide and that all analy­
ses have their strengths and weaknesses. At the end
of all of the diagnostic and planning appointments
it is a patient, and not a radiograph, that the team
is delivering treatment to and clinical impression
and judgement should always take precedence over
numerical values.
2.6.4  Superimposition
Superimposition is a technique that readily allows
differences between two or more cephalograms to be
identified graphically by over-laying them. This may
be required to monitor facial growth, assess treat­
ment changes, or quantify relapse.
Monitoring growth
Serial cephalograms are useful in assessing whether
jaw growth is ongoing prior to surgery. Figure 2.37
shows an example of progressive mandibular growth
between the ages of 17 and 20 years of age in a male
with a class III jaw relationship and increased vertical
dimension.
Figure 2.37  Class III growth shown using superimposed
sequential lateral cephalometric tracings.

50
Handbook of Orthognathic Treatment
• Correct positioning of the head is essential in
assessing the jaw relationship and any facial
asymmetry.
• Objective soft tissue analysis, carried out on cor­
rectly orientated photographs, can be a valuable
adjunct to clinical assessment.
• Assessment of the dental arches should include a
basic space analysis and measurement of the depth
of the curves of Spee.
• Assessment of the occlusion should include the
incisor relationship and extent of dento-alveolar
compensation in all three planes, as well as any
transverse arch width discrepancy.
• The dental centrelines should be assessed in rela­
tion to their respective jaws, as well as the facial
midline.
• If a mandibular asymmetry is present, it is essential
to determine whether it is truly skeletal in origin,
or the result of a displacement due to occlusal
interference.
• Study models and photographs are essential in
monitoring progressive conditions such as class III,
asymmetry and anterior open bite.
• Stereophotogrammetry is the only method of
recording a patient’s true 3D facial characteristics,
quantifying 3D soft tissue growth changes and
monitoring asymmetries.
• Cephalometric analysis is a valuable adjunct to
clinical assessment, but the clinician must be aware
of its limitations, particularly in assessing the
antero-posterior jaw relationship un relation to the
anterior cranial base.
• Cone beam CT imaging is not usually required at
the initial assessment stage, except for patients
with complex asymmetries.
• The routine capture of CBCT, pre- and post-
operatively, allows surgical intervention to be
planned appropriately and gives the opportunity
to evaluate and measure surgical changes in 3D.
2.9  Recommended further reading
Jacobson, A. and Jacobson, R.L. (2006) Radiographic cepha­
lometry: From Basics to 3D Imaging, 2nd edn. Quintessence
Publishing Co, Inc.
Naini, F.B. and Gill, D.S. (2008) Facial aesthetics: 2. clinical
assessment. Dent Update, 35 159–170.
Proffit, W.R. Fields, H.W. and Sarver, D.M. (2013) Contempo­
rary Orthodontics, 5th edn. Sections II and III. Elsevier.
2.7.1  Condylar hyperplasia
Where the patient reports or shows signs of a pro­
gressive mandibular asymmetry, this will require
monitoring. It may be appropriate to consider radio
isotope (technetium99) scanning in an attempt to
confirm the over growth of the suspected condyle in
comparison to the opposite side. Negative findings
are inconclusive as excessive growth tends to occur
in phases, so that the scan may take place during a
period of quiescence.
The diagnosis of hemi-mandibular hypertrophy
and condylar hyperplasia can be readily confused and
they can co-exist in the same patient. The hallmarks
of hemi-mandibular hypertrophy are bowing of the
inferior border of the mandible and inferior displace­
ment of the ID canal on the affected side, which
helps with the diagnosis and treatment plan.
2.7.2  Acromegaly
Acromegaly is caused by excessive growth hormone
production in adulthood, usually due to pituitary
adenoma. Initial diagnosis is likely to be through
patient history and clinical signs, which are as
follows:
• Late mandibular growth, typically causing a class
III malocclusion with spacing of the lower
incisors.
• Thickening of the facial skin and lengthening of
the lips.
• Thickening of the fingers.
Previous family or school photographs of the
patient are particularly valuable in identifying the soft
tissue changes, which will tend to cause lengthening
of the lips and a reduced display of the upper incisors.
Reported increases in glove and ring size are typical
complaints. Where suspected, referral to an endo­
crinologist will be required for assessment of growth
hormone levels and appropriate management.
2.8  Summary
• Prior to dentofacial assessment, a thorough history
should be taken from the patient regarding their
presenting problem, their general and dental
health.
• A social history is important, although this is pri­
marily be the remit of the psychologist, if one is
available.
• A full facial assessment should be carried out sys­
tematically from the lateral right and left, frontal,
bird’s eye and worm’s eye views.

Intended learning outcomes
By the end of this chapter the reader should:
• Understand the three fundamental steps in
orthognathic treatment planning.
• Understand the four keys to hard tissue planning.
• Understand the difference between initial,
combined treatment planning and final surgical
planning.
• Understand the interaction between pre-surgical
orthodontic planning and provisional surgical
planning.
The treatment planning process
3
Chapter overview
Intended learning outcomes, 51
3.1 Introduction, 51
3.2 Three fundamental planning steps, 51
3.2.1 Envisaging the desired aesthetic changes, 51
3.2.2 Deciding on the required jaw movements, 52
3.2.3 Planning orthodontics to allow the required jaw
movements, 52
3.3 Four keys to dento-skeletal planning, 52
3.3.1 Upper incisor and maxillary position, 53
3.3.2 Occlusion and mandibular position, 55
3.3.3 Maxillo-mandibular complex rotation, 58
3.3.4 Chin position, 58
3.4 Final surgical planning, 59
3.4.1 Final planning steps, 60
3.4.2 Photo-cephalometric prediction, 60
3.4.3 Model surgery, 61
3.5 Summary, 61
3.6 Recommended further reading, 61
No individual part of the plan can be made in isola­
tion and a continuous, interactive thought process is
required to arrive at the optimal combination of
orthodontic and surgical movements.
3.2  Three fundamental planning steps
The planning process typically involves three basic
steps:
1. Envisaging the main soft tissue changes required
to produce harmonious facial aesthetics.
2. Deciding the approximate skeletal jaw movements
required to produce the desired aesthetic result.
3. Planning the pre-surgical orthodontics, such that
correcting the occlusal disharmony will result in
the required jaw movements.
3.2.1  Envisaging the desired aesthetic
changes
This relies on the experience and judgement of
the clinicians to a large extent and, even between
51
3.1  Introduction
Treatment planning for the orthognathic patient
should be an inter-disciplinary process, carried out
between the team members, with the patient present.
Following appropriate diagnosis the clinicians will be
able to discuss the proposed dental and skeletal
movements, taking the patient’s concerns into
account.
Handbook of Orthognathic Treatment: A team approach, First Edition. Ashraf Ayoub, Balvinder Khambay, Philip Benington,
Lyndia Green, Khursheed Moos, and Fraser Walker.
© 2014 John Wiley & Sons, Ltd. Published 2014 by John Wiley & Sons, Ltd.

52
Handbook of Orthognathic Treatment
leave the patient with an unattractive appearance
of bi-maxillary protrusion and enophthalmos.
These effects are not entirely predictable and can
be controlled by the surgeon to some extent (see
Chapter 7), but they will tend to be greater with
larger maxillary movements. Care must be taken to
formulate a plan that will adequately correct the jaw
disharmony, but also limit the unaesthetic side
effects. It is important to take into account the shape
of the nose and the alar base width, in proportion to
the rest of the face, along with the upper facial mor­
phology, particularly where a large maxillary advance­
ment will be required.
3.2.3  Planning orthodontics to allow the
required jaw movements
Pre-surgical orthodontics should be aimed at placing
the teeth in a position that allows the jaws to be
surgically moved by the amount estimated to produce
the desired facial aesthetic changes. A key feature of
this approach is that the degree of incisor decompen­
sation should be tailored to allow the planned surgi­
cal movements, which involves setting a target
overjet (class II cases) or reverse overjet (class III
cases). This is conceptually different to an approach
where the primary aim is to set the incisor inclina­
tions to their cephalometric norms, with the result­
ing overjet then dictating the size of the surgical
correction (see also Chapter 4).
The amount of incisor decompensation that will be
required can be aided by profile cephalometric plan­
ning at this stage, but its validity may be limited until
the final tooth positions are known at the end of
pre-surgical orthodontics.
3.3  Four keys to dento-skeletal
planning
Whilst the initial step in the planning process is
envisaging the final aesthetic outcome, the delivery
of treatment usually takes place in the reverse
sequence. The teeth are orthodontically positioned
first, then the jaws surgically moved to produce the
soft tissue changes. The orthodontic tooth move­
ments and the surgical jaw movements are inter-
dependent and must be planned together. In most
cases the major orthodontic tooth movements will
be carried out first but, at the initial planning stage,
it can be difficult to predict how accurately the ortho­
dontist will be able to achieve the desired tooth
positions. The initial surgical plan can therefore
only be approximate and it is not until the patient is
Figure 3.1  Superimposition of mean pre-surgical (white)
and post-surgical (red) three-dimensional mesh diagrams
of Le Fort I advancement osteotomy patients showing
flaring of the alar base.
experienced clinicians, there can be disagreement
regarding the facial aesthetic goals. Where this occurs,
it is particularly important to ensure that planning
remains focused on the patient’s concerns. Guide­
lines can help in determining the site and magnitude
of the discrepancy and have been discussed in
Chapter 2.
Photo-cephalometric planning may be required at
this stage when maxillo-mandibular disharmony is
mild and it is not clear which single jaw correction
would produce the best results, or in borderline cases
where it is not clear if single or bi-maxillary surgery
is required.
3.2.2  Deciding on the required jaw
movements
The soft tissue changes, in response to surgical move­
ment of the underlying bones, vary depending on the
anatomical level (see Chapter 6). This is not an exact
science, since the evidential basis for hard-to-soft
tissue movement ratios is limited and there is consid­
erable individual and racial variation.
In addition, soft tissue changes occur not just in
profile, but in three dimensions and the clinicians
should be mindful of potentially adverse effects. In
particular, with Le Fort I osteotomy:
• The alar base has a tendency to flare, even where
there is no vertical impaction of the maxilla
(Figure 3.1).
• The nasal tip turns upwards with maxillary
advancement and impaction.
• Correction of severe maxillary deficiency, accompa­
nied by zygomatic and infra-orbital deficiency, can

The treatment planning process
53
the maxilla looking slightly deficient, para-nasal aug­
mentation using bone grafts can be considered as a
surgical adjunct.
Where the degree of maxillary retrusion is consid­
ered severe enough to require surgical advancement,
it is important to ensure that the target overjet is
sufficient to allow the maxilla to be advanced by a
worthwhile amount (i.e. at least 4mm), whilst still
keeping the mandibular advancement to within an
achievable surgical limit (i.e. approximately 10mm
maximum with a sagittal split osteotomy). An overjet
of 8mm is therefore about the maximum that will be
compatible with bi-maxillary advancement osteot­
omy in a class II patient. An adjustment to this cal­
culation will be necessary where the maxilla also
needs to be impacted, allowing a degree of mandibu­
lar advancement through autorotation. In some
cases, with severe mandibular deficiency, other surgi­
cal techniques, including inverted ‘L’ osteotomy with
bone graft, or distraction osteogenesis, may be
considered.
In cases where prominence of the anterior part of
the maxilla (pre-maxilla) has resulted in dento-
alveolar protrusion, an anterior maxillary osteotomy
may be required. This is often carried out in conjunc­
tion with extraction of upper first premolars and may
be a more predictable and quicker alternative to
orthodontic retraction of the teeth.
Class III skeletal pattern.  In class III cases, where
maxillary deficiency has been diagnosed, the plan
will involve advancement of the maxilla. This has
two specific objectives:
1. To produce the envisaged mid-facial soft tissue
aesthetics.
2. To place the upper incisors in the most aestheti­
cally pleasing position.
The upper incisors will often be proclined in com­
pensation for the underlying skeletal discrepancy and
may need to be orthodontically retroclined to place
them at the most aesthetically pleasing inclination.
Anterior open bite.  Where an anterior open bite
requires correction by posterior impaction of the
maxilla, surgery will have a retroclining effect on the
upper incisors, which should be compensated for
in the pre-surgical orthodontic preparation (Figure
3.2). Where segmental osteotomy is required to level
the maxillary arch, due to a severe curve of Spee, the
upper incisor inclination will be determined by the
positioning of the anterior segment to a large extent.
This may be amenable to some post-surgical
adjustment.
seen again following the completion of pre-surgical
orthodontics, that the definitive surgical plan can be
finalised.
The following four keys should be considered in
planning the dento-skeletal movements:
1. Upper incisor and maxillary position.
2. Occlusion and mandibular position.
3. Maxillo-mandibular complex rotation.
4. Chin position.
3.3.1  Upper incisor and maxillary position
The first step is deciding where to place the upper
incisors in all three planes of space, and their final
position will be the net result of both orthodontic
and surgical movements.
Antero-posterior positioning
Planning the optimal antero-posterior position for
the upper incisors must take into account their posi­
tion in the horizontal plane as well as their inclina­
tion. Antero-posterior orthodontic adjustment of the
incisors pre-surgically has two objectives:
1. To help achieve the target overjet or reverse overjet
as part of incisor decompensation.
2. To ensure that they are left at the most aestheti­
cally pleasing inclination following orthognathic
surgery.
These objectives are inter-linked and must be con­
sidered simultaneously. There are specific planning
considerations that relate to the different malocclu­
sion groups.
Class II skeletal pattern.  In many class II, divi­
sion 1 cases, the upper incisors will be at an aestheti­
cally acceptable inclination and will require minimal
adjustment. If they are proclined and the plan is to
retract them to a more average inclination, it must
be borne in mind that the upper lip will drop back
in response to this, which can accentuate any under­
lying deficiency of the maxilla. In Class II, division 2
cases the upper central incisors will require proclina­
tion and this will result in some increase in lip
support.
Where a degree of maxillary deficiency does accom­
pany the mandibular deficiency (bi-maxillary retru­
sion), a decision must be made as to whether the
position of the maxilla also warrants surgical correc­
tion to bring the upper incisors into an aesthetically
pleasing position. In cases where the maxillary defi­
ciency is mild, leaving the upper incisors slightly
proclined may allow adequate advancement of the
mandible, whilst avoiding the need for maxillary
osteotomy. However, in cases where this may leave

54
Handbook of Orthognathic Treatment
acceptable. An adjunctive surgical lip lengthening
procedure, such as a ‘V-Y’ closure of the incision of
the muco-buccal fold and the mucosa of the lip will
usually be beneficial in such cases.
Reduced vertical incisor display.  In class III
patients with a reduced lower anterior vertical
dimension, the maxilla will often be vertically defi­
cient and the upper incisor show will be reduced.
The patient will often exhibit over-closure of the
mandible with their posterior teeth in contact. This
is because the freeway space is increased and it is
important that planning is carried out with the
mandible in its rest position (see Figure 6.4). This
gives an indication of the amount of vertical space
available for maxillary down-grafting, as well as
giving a more accurate impression of the antero-
posterior jaw relationship.
Incisal show may also be reduced in class II cases
due to restriction of the vertical development of the
anterior maxilla because of para-functional habits i.e.
tongue thrust or digit sucking. The uppper curve of
Spee will be accentuated and the decision to level this
surgically (by a segmental approach) or orthodonti­
cally, will depend on the severity of the curve and
operator preferences (see Chapters 4 and 7).
Borderline cases.  In cases where the vertical incisor
position is only mildly abnormal, the possibility of
correcting it may depend on the rest of the surgical
plan. For example, if the maxilla is to be advanced,
there will be an opportunity to simultaneously adjust
its vertical position in order to achieve the most ideal
result possible. On the other hand, if the maxilla is
already in the correct position antero-posteriorly, it
may not be warranted to perform a Le Fort I proce­
dure for the sake of a relatively minor discrepancy
that the patient is not overly concerned about.
Transverse positioning
Where the upper dental centreline is displaced to one
side, it should ideally be a goal of pre-surgical ortho­
dontics to correct it (see Chapter 4). If a Le Fort I
osteotomy is planned, there may be some scope to
rotate the maxilla to correct the centreline surgically,
but, this movement can potentially disrupt the trans­
verse buccal segment occlusion.
Where there is a transverse arch discrepancy, the
maxillary dental arch is most commonly too narrow.
Hand-articulating the study models, or requesting
some preliminary model surgery, can often be helpful
in assessing the amount of expansion that would be
required to achieve arch coordination. The com­
Vertical positioning
Canting of the occlusal plane.  Canting of the
maxillary occlusal plane can be levelled surgically
and this must be planned to achieve the correct verti­
cal position of the upper incisors on both sides.
Where no other movement of the maxilla is required
and the discrepancy is mild, it may be acceptable to
leave the cant uncorrected. Where it is part of a lower
facial asymmetry involving the mandible, adequate
surgical correction of the overall bi-maxillary vertical
asymmetry will depend on achieving a level maxil­
lary occlusal plane.
Excessive incisor show – the ‘gummy’ smile. 
Where the vertical display of the upper incisors (at
rest and on smiling) is significantly increased, it must
be decided whether or not this requires surgical cor­
rection. This will be largely driven by the patient’s
concerns, as well as their malocclusion. In patients
with a short upper lip and a ‘gummy smile’, it may
be that full correction of the vertical incisor-to-lip
relationship will be unrealistic without impacting the
maxilla excessively and compromising the overall
vertical facial proportions. In such cases, leaving a
small amount of gingival display on smiling will have
to be accepted, but this will usually be aesthetically
Figure 3.2  Pre-surgical cephalometric tracing of a class III
patient with an anterior open bite. The proclination of the
upper incisors has been maintained during pre-surgical
orthodontics to allow for the retroclining effect of the
planned posterior maxillary impaction.

The treatment planning process
55
depend on whether or not an increase in lower ante­
rior face height is required (see Chapter 7).
Anterior open bite.  Where an anterior open bite is
due to posterior vertical maxillary excess or vertical
deficiency of the mandibular ramus, this is com­
monly corrected through posterior maxillary impac­
tion which allows the mandible to auto-rotate into
the correct vertical position, bringing the incisors
into occlusion (Figure 3.4).
Asymmetry.  Where a vertical asymmetry of the
mandible is present, there will usually be a cant of
the mandibular occlusal plane. If this has developed
during facial growth, the maxillary plane will usually
be canted as well and the plan will already include
its correction (see previously). If the mandibular
asymmetry has developed after the cessation of
normal facial growth, then there may be a lateral
open bite on the affected side. In either case, the
mandibular occlusal plane will require surgical level­
ling, in order to correct the occlusion. Where the
problem is due to excessive ramus length on one
side, this will require surgical reduction of the
affected side, or lengthening of the opposite side, or
a combination of both. Where there has been restric­
tion of vertical growth on one side, it may be neces­
sary to consider a ramus lengthening procedure (see
Chapter 7). In cases where there is no significant
disparity of the ramus lengths, vertical mandibular
asymmetry can be corrected using sagittal split
osteotomy.
Angle of the mandibular plane.  It is important
to take the mandibular plane into account at the
planning stage, because its angle can affect the objec­
tives of both pre-surgical orthodontics and surgery.
Post-surgical profile balance may be improved where
the lower incisor inclination has been adjusted to
compensate for the mandibular plane angle being
outside its normal range. Figure 3.5 illustrates a class
III patient with an increased FMPA and correspond­
ingly retroclined lower incisors. Surgical correction
was carried out by means of a Le Fort I maxillary
advancement and a bilateral sagittal split mandibular
set back. No vertical change of the maxilla was
required and so the FMPA remained largely unchanged
as a result of surgery. The lower incisors were only
partially decompensated, such that a balanced profile
would be achieved. Had full decompensation been
carried out, the result would have been over-correction
and a convex profile, due to the backwardly angled
monly used techniques for widening the maxillary
arch are outlined in Chapter 4 and the surgical tech­
niques are described in Chapter 7. In the more severe
cases, accepting a bilateral buccal segment cross-bite
may be the most sensible approach, particularly if the
patient is not greatly concerned about the aesthetics
of their narrow upper dental arch.
3.3.2  Occlusion and mandibular position
Antero-posterior correction
Having planned the upper incisor and maxillary posi­
tion, the antero-posterior mandibular position can be
addressed. In cases where mandibular surgery only or
bi-maxillary surgery is planned, the mandible is
moved to set the teeth into the planned post-surgical
occlusion, through either setback or advancement.
As previously stated, incisor decompensation
should be tailored to deliver optimal aesthetics.
Another aspect of this concept is that the amount of
decompensation carried out could, in some cases,
mean the difference between single and double jaw
osteotomy. Although the attainment of ideal aesthet­
ics is important, the risks of bi-maxillary osteotomy
must be carefully weighed up in cases where a single
jaw procedure would still be estimated to produce a
satisfactory result (Figure 3.3).
In more severe cases, where bi-maxillary oste­
otomy is inevitable, partial decompensation may
be planned to limit the size of the jaw move­
ments, thereby reducing surgical complexity and
relapse tendency, whilst still achieving satisfactory
aesthetics.
Vertical correction
Deep overbite.  Class II patients sometimes present
with a reduced lower anterior face height and a ten­
dency to parallelism of the jaws (see Chapter 2). In
such cases, treatment will be aimed at increasing the
lower anterior face height. A common approach to
achieve this is to plan to maintain the lower curve of
Spee until after mandibular advancement surgery, in
order to produce a ‘three-point landing’ (occlusal
contact between the incisors and terminal molars
only). The resulting lateral open bites must then be
closed orthodontically after surgery (see Chapter 4).
In cases with a severe lower curve of Spee, where
orthodontic levelling is unlikely to be achievable, it
may be necessary to plan for a sub-apical procedure
or body osteotomy, to set down the lower anterior
labial segment. Which procedure is selected will

56
Handbook of Orthognathic Treatment
Figure 3.3  Class III patient with compensated upper and lower incisors (a, b, c). Initial cephalometric planning (d)
revealed that complete upper incisor decompensation (requiring extractions), would result in bi-maxillary osteotomy.
Accepting the upper incisor proclination allowed occlusal correction with maxillary osteotomy only, which produced a
satisfactory aesthetic result (e). Tracings produced using OPAL (British Orthodontic Society).
a)
d)
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ϴϰ
Ͳϱ
ϭϮϴ
ϳϵ
Ϯϯ
&W
ϭϮϱ
c)
b)
e)

Figure 3.4  These superimposed pre- (red) and post-surgical (blue) cephalometric tracings demonstrate closure of an
anterior open bite by mandibular autorotation, following posterior maxillary impaction. Produced using OPAL (British
Orthodontic Society).
Figure 3.5  Cephalometric tracing of a class III patient with increase FMPA and retroclined lower incisors, planned for
bi-maxillary osteotomy (a). Because surgery was not expected to correct the FMPA, the lower incisors were only partially
decompensated (b). This allowed satisfactory profile balance to be achieved without resort to an advancement
genioplasty (c). Produced using OPAL (British Orthodontic Society).
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ϳϮǑ
ϯϴǑ
ϯϲǑ
ϭϬϳǑ
ϴϮǑ
ϯϴǑ
ϯϲǑ
a)
b)
c)
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58
Handbook of Orthognathic Treatment
Figure 3.6  Superimposition of pre- and post-surgical
profile photographs showing the increase in lower
anterior face height achieved as a result of the ‘three-
point landing’ approach to correcting a deep overbite in
a class II patient.
symphysis, which might then have required an
advancement genioplasty.
The converse is true for low angle cases where
leaving the lower incisors proclined, in anticipation
of a reduced post-surgical FMPA, will help to com­
pensate for the progenia that tends to accompany
forward mandibular growth rotation.
Transverse positioning
If there is a significant medio-lateral mandibular
asymmetry, with a corresponding dental centreline
displacement, then surgical correction will be
achieved through asymmetric mandibular osteot­
omy, which will correct the centreline along with the
chin point. This will allow the ideal planned occlu­
sion to be achieved with the maxillary centreline in
harmony with the middle of the face.
If the mandibular centreline is not coincident with
the chin point and cannot be easily corrected ortho­
dontically, the following two scenarios may occur:
1. If maxillary surgery only is planned, the upper
centreline will finish off-centre, assuming that the
planned occlusion has coincident centrelines.
2. If mandibular or bi-maxillary surgery is planned,
it will be necessary to carry out asymmetric man­
dibular osteotomy to leave the upper and lower
centrelines coincident. This will then result in the
chin point being off-centre.
In the first case, one option is to compromise the
planned occlusion by leaving the centrelines non-
coincident. In the second case, the resulting man­
dibular asymmetry can potentially be addressed with
a lateral sliding genioplasty (see Chapter 7).
3.3.3  Maxillo-mandibular complex rotation
The morphology of the mandible varies considerably
between patients with extremes of vertical jaw
growth, according to its direction of growth rotation
(see Chapter 2). A shallow or steep mandibular plane
often contributes to the poor aesthetics that short-
and long-faced patients complain about and seek cor­
rection of. Whilst it is not always possible, or indeed
necessary, to surgically correct the rotation of the
jaws as part of orthognathic treatment, it should be
considered in certain situations.
Clockwise rotation
In class II cases with reduced vertical dimensions,
carrying out a mandibular advancement to a three-
point landing will increase the lower anterior face
height through downward and backward rotation of
the mandible (Figure 3.6). There will also be a cor­
responding increase in the gonial angle and the
mandibular plane will steepen to a certain extent
(see also Case Report 1). In extreme cases, where cor­
rection of the angles of both the occlusal and man­
dibular planes together is required, it may be
appropriate to carry out bi-maxillary osteotomy to
rotate both jaws downward and backward (clock­
wise) (Figure 3.7b).
Anti-clockwise rotation
In severe anterior open bite cases with an extreme
backward rotation of the mandible, the mandibular
plane will be steep and the ramus short, with an
obtuse gonial angle. Closing the anterior open bite
through posterior impaction of the maxilla alone
will allow a certain amount of upward and forward
(anti-clockwise) auto-rotation of the mandible, with
a corresponding flattening of the mandibular plane.
In cases where greater rotation is required, an option
may be to increase the ramus heights through an
‘inverted ‘L’ osteotomy or distraction osseogenesis,
producing an anti-clockwise rotation of the mandib­
ular and occlusal planes and a reduction of the gonial
angle (Figure 3.7a). The risks of these procedures
must be carefully evaluated against the anticipated
benefits (see also Chapter 7).
3.3.4  Chin position
The final part of the provisional surgical plan is the
positioning of the chin, which must be considered in
all three planes of space (see also Chapter 7).
Adjusting chin prominence
Following correction of a sagittal jaw discrepancy
there may be a need to adjust the antero-posterior
position of the soft tissue chin point to achieve the
best possible profile balance. Advancement genio­

The treatment planning process
59
Figure 3.7  Superimpositions of pre-surgical (red) and post-surgical (blue) cephalometric tracings illustrating rotation of
the maxillo-mandibular complex. (a) Anterior open bite case in which the mandibular and occlusal planes were rotated
anti-clockwise with anterior maxillary impaction and inverted ‘L’ ramus lengthening. (b) Deep overbite case in which the
occlusal and mandibular planes were rotated clockwise with bi-maxillary osteotomy. Produced using OPAL (British
Orthodontic Society).
a)
b)
plasty is most often required to compensate for the
backward slope of the mandibular symphysis, in
cases where the mandibular plane angle will still be
increased following surgery. Predicting the soft tissue
movement that will be achieved through an advance­
ment genioplasty is usually straightforward since
there is a one-to-one ratio of hard-to-soft tissue
movement at the level of pogonion (see Chapter 6).
A set-back genioplasty is potentially required where
progenia is predicted after surgical jaw correction in
low angle, deep bite cases. In isolation, it tends to
result in a poor lower lip form (see below) and is not
commonly performed by our team, but it may
produce a satisfactory result when combined with a
vertical augmentation. Correcting the mandibular
plane angle in a short-face patient will also help to
reduce post-surgical progenia by rotating the chin
downwards and backwards (see Section 3.3.3).
Adjusting lower anterior face height
In cases where the lower anterior face height is pre­
dicted to be deficient or excessive following surgical
jaw correction with Le Fort I osteotomy, there may
be a need to carry out a vertical augmentation or
reduction genioplasty to achieve the correct vertical
facial proportions. This also normalises the lower lip
length and the proportions of the lower anterior
facial height.
Improving lower lip curvature
One of the aesthetic features that orthognathic treat­
ment should aim to correct is the labio-mental fold,
or lower lip curvature (see Figure 2.5). The post-
surgical shape of the lower lip and the competence
of the lips are closely linked to the inclination of the
lower incisors, the lower anterior face height and the
prominence of the mandibular symphysis. Normal
lip curvature and competence should therefore result
from placing the chin or the mandible in its correct
antero-posterior and vertical positions, as described
above. Carefully planned decompensation of the
lower incisors will also improve the curvature or the
lower lip and this should be considered when plan­
ning pre-surgical orthodontics.
Disguising mandibular asymmetry
In some cases, a mild medio-lateral mandibular asym­
metry may have to be accepted as part of the surgical
plan and may require disguising in order to optimise
the overall aesthetic result (see Section 3.3.2). In such
situations a sliding genioplasty can be planned to
adjust the chin point in either direction. This is an
easy manoeuvre to add if a genioplasty has already
been planned to adjust the chin point in the antero-
posterior or vertical dimensions.
3.4  Final surgical planning
For most patients, pre-surgical orthodontics will be
required and this will be carried out according to the
prescribed initial plan. When the orthodontic prepa­
ration is complete, the patient is seen again on the
combined clinic for final surgical planning. At this
stage, it is essential to reassess the patient’s dento-

60
Handbook of Orthognathic Treatment
Figure 3.8  Flow diagram of the treatment planning process.
MAXILLO-MANDIBULAR
COMPLEX ROTATION
Clockwise rotation
Anti-clockwise rotation
OCCLUSION AND
MANDIBULAR POSITION
A-P correction
Overbite / AOB
Mandibular plane angle
Vertical asymmetry
Transverse asymmetry
Initial
combined
planning
Pre-surgical orthodontics
Final surgical planning
Orthognathic surgery
Post-surgical orthodontics
Post-surgical maxillary
incisor position
Post-surgical occlusion
and mandibular position
Final treatment result
UPPER INCISOR AND
MAXILLARY POSITION
Facial soft tissue aesthetics
A-P position
Vertical position
Occlusal canting
Upper centre line
CHIN POSITION
A-P position
Vertical position
Transverse position
facial dysmorphology and ensure that their concerns
are fully taken into account.
3.4.1  Final planning steps
The final planning steps are then as follows:
1. Envisage the soft tissue changes required for
optimal facial aesthetics.
2. Plan the surgical movements required to:
a. Produce the desired soft tissue changes.
b. Place the teeth in the most aesthetic position.
c. Achieve the optimal occlusion.
3.4.2  Photo-cephalometric prediction
Photo-cephalometric profile planning or if available,
three-dimensional virtual planning, (see Chapter 6)
is mandatory at this stage to:
• Assist with planning the magnitude of the jaw
movements. This is particularly important where
the patient is on the borderline between one- or
two-jaw surgery and where the correct ratio of
bi-maxillary jaw movements is difficult to envisage.
• Help decide whether or not a genioplasty is needed
to improve profile balance.

The treatment planning process
61
• Provide the patient with a graphic depiction of
the soft tissue changes that surgery is predicted to
achieve.
3.4.3  Model surgery
The next stage is the technical planning, ideally
carried out on an orthognathic articulator (see
Chapter 5). It is essential that the model surgery and
the photo-cephalometric prediction are well matched,
to ensure that the planned surgical movements
produce a harmonious profile in addition to achiev­
ing the planned occlusion.
In cases involving correction of facial asymmetries,
three-dimensional hard tissue planning, based on a
CBCT-derived model of the skull, is extremely useful
and a technique for this is described in Chapter 5.
3.5  Summary (Figure 3.8)
• Combined surgical orthodontic treatment plan­
ning involves three fundamental steps:
○ Envisaging the desired dentofacial aesthetic
changes.
○ Deciding on the jaw movements required to
produce those aesthetic changes.
○ Planning the pre-surgical orthodontics such that
correcting the occlusal disharmony will result in
the required jaw movements.
• Execution of the treatment plan takes place in the
reverse direction, with the pre-surgical orthodontic
tooth movements determining the size of the surgi­
cal jaw correction, which then produces the soft
tissue aesthetic changes.
• There are four key areas in dento-skeletal planning:
○ Upper incisor and maxillary position.
○ Occlusion and mandibular position.
○ Maxillo-mandibular complex rotation.
○ Chin position.
• Incisor decompensation should be planned to
produce a target overjet that allows the desired size
of antero-posterior jaw correction.
• The surgical plan can only be provisional at the
initial planning stage because it is difficult to
predict how accurately the orthodontist will be
able to achieve the planned tooth positions.
• Final surgical planning can only be carried out
once the pre-surgical orthodontics is complete and
the final tooth positions are known.
3.6  Recommended further reading
Proffit W.R., White R.P. and Sarver D.M. (2002) Contemporary
Treatment of Dentofacial Deformity. St. Louis, Mosby.

Intended learning outcomes
By the end of this chapter the reader should:
• Be aware of the indications for pre-surgical
orthodontics in orthognathic patients.
• Understand the objectives of pre-surgical
orthodontics.
• Be aware of the scope and limitations of pre-
surgical orthodontics.
• Understand the role of orthodontic appliances in
the peri-operative period.
• Be aware of the scope and limitations of
orthodontics in the immediate post-operative
healing phase.
• Understand the objectives of post-surgical
orthodontics.
• Be aware of the advantages and disadvantages of
carrying out surgery before orthodontics.
The role of orthodontics
4
Chapter overview
Intended learning outcomes, 62
4.1 Introduction, 62
4.2 Pre-surgical orthodontics, 63
4.2.1 Factors affecting incisor decompensation, 63
4.2.2 Control of incisor decompensation, 65
4.2.3 Vertical tooth movements, 67
4.2.4 Transverse tooth movements, 69
4.2.5 Orthodontic preparation for segmental
surgery, 71
4.2.6 Progress monitoring, 71
4.3 Peri-operative orthodontics, 71
4.3.1 Fixed appliance preparation for surgery, 71
4.3.2 Inter-maxillary fixation, 72
4.3.3 The occlusal wafer, 72
4.3.4 Orthodontic procedures in theatre, 73
4.4 Post-surgical orthodontics, 74
4.4.1 Post-surgical healing phase, 74
4.4.2 Post-surgical tooth movement, 75
4.4.3 Retention, 75
4.5 Surgery before orthodontics, 76
4.5.1 Advantages, 76
4.5.2 Disadvantages, 76
4.6 Surgery without orthodontics, 77
4.7 Complications of orthodontic
treatment, 78
4.7.1 Iatrogenic tooth damage, 78
4.7.2 Loss of periodontal support, 78
4.8 Summary, 78
4.9 Recommended further reading, 79
4.1  Introduction
Orthodontic treatment is usually an integral part of
contemporary orthognathic treatment. In most cases,
the attainment of a satisfactory post-surgical occlu­
sion will require the use of fixed appliances to achieve
optimal arch coordination and inter-digitation. As
explained in Chapter 3, the magnitude of surgical jaw
correction that can be achieved is, to a large extent,
62
• Be aware of the possible indications for carrying
out surgery without adjunctive orthodontics.
• Be aware of the common complications
associated with orthodontic treatment in
orthognathic patients.
Handbook of Orthognathic Treatment: A team approach, First Edition. Ashraf Ayoub, Balvinder Khambay, Philip Benington,
Lyndia Green, Khursheed Moos, and Fraser Walker.
© 2014 John Wiley & Sons, Ltd. Published 2014 by John Wiley & Sons, Ltd.

The role of orthodontics
63
required vary with the type of malocclusion. In class
II, division 1 cases the lower incisors typically need
to be retracted from a proclined position, whilst in
class III cases they need to be proclined. In the upper
arch, the opposite movements will generally be
needed. The notable exceptions to this are class II,
division 2 malocclusions, where the upper incisors
require proclination from their retroclined pre-
treatment positions.
Complete decompensation of the incisors involves
correction of their inclinations to their respective
cephalometric norms, which is often appropriate.
However, as stated in Chapter 3, there are also situa­
tions where partial decompensation is desirable and
this must be agreed at the planning stage so that the
orthodontist has clear goals. The main factors that
influence incisor decompensation are as follows:
• Crowding and spacing of the teeth.
• Previous extractions.
• Soft tissue resistance.
• Magnitude of surgical jaw movements.
• Mandibular plane angle.
• Type of maxillary surgery.
• Quality of the planned occlusion.
• Limiting factors.
Crowding and spacing of the teeth
Space is required for incisor retraction and crowding
assists proclination. Figure 4.1 illustrates how decom­
pensation is largely facilitated by the presence of
crowding, in a class III case where the lower incisors
are retroclined. Conversely, in a class II case where
the lower incisors are proclined and there is no
spacing, extractions will be necessary to allow decom­
pensation (Figure 4.2). For these reasons, the ideal
amount of decompensation may not always be easy
to achieve.
dictated by the size of the overjet (positive or nega­
tive), which often needs to be adjusted through care­
fully planned incisor decompensation. It also stands
to reason that the stability of the surgical jaw correc­
tion should be assisted by a well inter-digitated
occlusion.
Whilst many patients seeking orthognathic surgery
report concerns regarding their facial aesthetics, a
large proportion are also unhappy with the appear­
ance of their teeth. The ideal alignment that modern
fixed appliance treatment can achieve helps to deliver
optimal dental aesthetics as part of the overall treat­
ment outcome.
It is logical to consider the role of orthodontics in
three stages: before surgery (pre-surgical); just before
and during surgery (peri-operative); and after surgery
(post-surgical).
4.2  Pre-surgical orthodontics
The tooth movements required to prepare a patient
for surgery should be carefully planned in all three
planes of space, with reference to the patient in the
clinic as well as appropriate diagnostic records. It is
essential to carefully document the orthodontic plan
in a way that can be readily referred to as treatment
progresses.
4.2.1  Factors affecting incisor
decompensation
Most orthognathic patients will have developed a
degree of incisor compensation as a result of their
disproportionate jaw growth (see Chapter 2). One of
the main aims of pre-surgical orthodontics is to
reverse these compensations. The tooth movements
Figure 4.1  Class III orthognathic typodont model showing: (a) Compensated and crowded lower incisors, and (b) the
proclining (decompensating) effect of incisor alignment.
a)
b)

64
Handbook of Orthognathic Treatment
In class III cases the amount of lower incisor pro­
clination that will be achieved as a result of crowding
should be assessed. As a general rule, each millimetre
of lower arch crowding will produce approximately
0.5mm of labial movement of the incisal edges, in
the midline. Equally, in a class II case, where retrac­
tion of the lower incisors is required, each millimetre
of space will allow 0.5mm of lingual movement.
Previous extractions
Previous extractions in either the upper or the lower
dental arch can present a problem in the execution
of decompensation. For example, in a class II case
such as that shown in Figure 4.3, the lower incisors
are proclined, but the patient has previously lost
lower premolars as part of earlier fixed appliance
treatment. Decompensation, through incisor retrac­
tion, will therefore be difficult, since further extrac­
tions are not an ideal option. Conversely, in the
severe class III malocclusion shown in Figure 4.4,
there has been previous loss of both lower first
Figure 4.2  Class ll, division 1 patient. (a) The lower incisors are proclined and mildy crowded, with no space for
retraction. (b) Pre-molar extractions have allowed lower incisor decompensation.
a)
b)
Figure 4.3  Class II occlusion (a) with lower incisor compensation and previous loss of both lower first premolars and
complete space closure (b).
a)
b)
premolars and subsequent extreme retroclination of
the lower labial segment. The spacing in the lower
dental arch will make proclination of the incisors
difficult without re-opening space for prosthetic
tooth replacement.
Figure 4.4  Class III patient with severe lower incisor
compensation and previous loss of both lower first
premolars leaving residual spaces.

The role of orthodontics
65
or retroclined incisors. In class II cases, incomplete
decompensation will tend to result in a class II molar
relationship when the check models are hand
occluded with the incisors in class I (Figure 4.5). In
class III cases the opposite will tend to be true,
although mild compensation of the incisors generally
produces quite a pleasing occlusion.
Whilst the correct torque and tip of the incisors
are important in achieving an ideal occlusion, the
orthodontist must also be aware of tooth-size discrep­
ancies. Most commonly, disproportionately small
upper lateral incisors can result in class II buccal
segment relationships and a decision has to be made
to either accept this compromised occlusion or leave
space around the lateral incisor for build-up to the
correct size.
Limiting factors
It is important to recognise the scope and limitations
of incisor decompensation for each patient and these
should inform the orthodontic planning process,
as outlined in Chapter 3. Decompensation should
not be planned simply to attain cephalometrically
‘normal’ incisor inclinations, which may not neces­
sarily be appropriate, or achievable, for an individual
patient.
4.2.2  Control of incisor decompensation
The inclination of the upper and lower incisors can
be controlled orthodontically to help achieve the
planned degree of decompensation, using the follow­
ing methods:
• Extraction pattern.
• Bracket prescriptions.
• Mechanics.
Soft tissue resistance
Teeth have to be moved within their soft tissue enve­
lope and the lower lip and tongue may offer resist­
ance to the proclination and retraction of incisors.
This problem is likely to increase with the severity of
the jaw discrepancy and, in class III cases, will also
depend on the muscular tone of the lower lip. There
are also the constraints of the alveolar bone which,
in non-growing patients, is of limited adaptability.
Careful anchorage management is required to ensure
that the crowding or spacing in the lower arch trans­
lates into the planned amount of incisor movement.
Magnitude of surgical jaw movements
As explained in Chapter 3, one of the main functions
of pre-surgical orthodontics is to create an overjet
(class II patients), or reverse overjet (class III patients),
that will allow the desired amount of surgical jaw
correction. If it is not possible to adequately decom­
pensate the incisors then the patient will be left with
a residual jaw discrepancy after surgery. Equally,
excessive decompensation will result in surgical over-
correction. Setting a ‘target (reverse) overjet’ is there­
fore helpful for the orthodontist and, if this is proving
difficult to achieve, it is advisable to take the patient
back to the planning clinic for a review of the treat­
ment objectives.
Mandibular plane angle
In patients where the mandibular plane angle (to
Frankfort Plane or horizontal reference plane) is pre­
dicted to be outside its normal range following
surgery, consideration should be given to adjusting
the lower incisor inclination, such that it will add
with the mandibular plane angle to approximately
120° after surgery (see also Chapters 2 and 3 and
Figure 3.5).
Type of maxillary surgery
Where the provisional surgical plan is to differen­
tially impact or down graft the maxilla, there will be
a corresponding change in the inclination of the
upper incisors. For example, where posterior impac­
tion is planned, the incisors will retrocline relative to
the Frankfort Plane (or horizontal reference line).
This should be compensated for by modifying the
extraction pattern, or adding torque to the archwire
(see also Chapter 3).
Quality of the planned occlusion
Incisor inclination directly affects the quality of the
buccal segment occlusion that can be achieved in
orthognathic patients, because proclined incisors
occupy more space in the dental arch than upright
Figure 4.5  Class II case following mandibular
advancement surgery, where the buccal segment
occlusion is still class II, due to under-torquing of the
upper incisors.

66
Handbook of Orthognathic Treatment
Intra-arch mechanics.  Resistance of unwanted
mesial movement of upper posterior teeth can be
increased by using anchorage reinforcement devices,
such as trans-palatal arches. They exert their effect by
maintaining the inter-molar width and, in the case
of the Nance arch, also engaging the mucosal surface
of the anterior palatal vault (Figure 4.7).
Temporary Anchorage Devices (TADs) are mini
screws that are placed in the alveolar bone to offer
points of absolute anchorage from which to apply
traction. They can provide direct or indirect anchorage
for mesio-distal and vertical tooth movements, either
by being placed buccally between the roots of the
Extraction pattern
Where compensation has resulted in significant
incisor proclination, extractions will usually be
required to retract them to the desired position. Typi­
cally, this will apply to lower incisors in class II cases
and upper incisors in class III cases. As a general rule,
the further forward the extractions are in the dental
arch, the more incisor retraction will result. For
example, extraction of first premolars will generally
allow more decompensation than extraction of
second premolars.
Bracket prescriptions
Pre-adjusted edgewise fixed appliances have first-
order (in-out), second-order (tip) and third-order
(torque) adjustments built into the individual brack­
ets. The amount of ‘torque’ in the incisor brackets
controls their inclination and therefore contributes
to the delivery of decompensation during pre-surgical
orthodontics. Different appliance prescriptions have
different torque values for the upper and lower inci­
sors and so may be more or less suitable as aids to
decompensation.
The MBT™ prescription.  One of the most common
currently used prescriptions, MBT™, has negative
torque in the lower incisor brackets and increased
torque in the upper incisor brackets, which is aimed
primarily at conserving anchorage in the orthodontic
camouflage treatment of class II malocclusions. This
prescription is advantageous in the pre-surgical prep­
aration of class II cases, where retraction of lower
incisors and the maintenance of a large overjet are
required. However, in class III cases it will tend to be
disadvantageous, limiting lower incisor proclination
and maintaining upper incisor proclination.
Individual adaptations.  Whilst some clinicians
may opt for customised prescriptions to ensure that
the brackets are working in sympathy with their
treatment goals in all cases, it is possible to make
certain adaptations that can help to overcome some
of these problems. For example, the torque values of
the lower incisor brackets can be changed from − 6°
to + 6° by inverting them, which will help to procline
the lower incisors in a class III case with minimal
crowding (Figure 4.6). In addition, incisor inclina­
tions can be adjusted by introducing third order
bends into stainless steel rectangular archwires.
Mechanics
In addition to the effects of the extraction pattern and
the appliance prescription, there are also a number of
intra- and inter-arch mechanical techniques available
to the orthodontist to control the incisor positions:
Figure 4.6  In this class III case with an absence of lower
incisor crowding, the lower MBT™ incisor brackets have
been inverted to convert 6° of lingual crown torque to 6°
of labial crown torque to encourage incisor proclination.
Figure 4.7  Example of a Nance palatal arch in a class lll
orthognathic patient requiring upper incisor retraction
along with first molar extractions. Anchorage
reinforcement of the second molars is acheived by a
combination of maintaining inter-molar width and
resisting tipping by engaging the anterior palatal vault
with the acrylic button.

The role of orthodontics
67
fixed appliances. Wearing these requires good
patient compliance but they allow at least small
adjustments to the overjet, or reverse overjet, when
the intra-arch methods of anchorage control have
been exhausted. Figure 4.9 shows a class II case in
which the occlusion on the first set of check models
during pre-surgical orthodontics was not ideal, due
to inadequate decompensation. The incisor inclina­
tions were then adjusted, using class III elastics,
producing an improved inter-digitation of the
buccal segments.
4.2.3  Vertical tooth movements
Patients with extreme vertical jaw disproportions will
usually have developed accentuated curves of Spee.
In anterior open bite cases this will tend to affect the
upper arch, whilst in deep bite cases it tends to affect
the lower arch (see Chapter 2). One of the treatment
objectives for orthognathic patients should be to
level the dental arches for an optimal occlusion. In
planning pre-surgical orthodontics, the following
factors must be taken into account:
upper first molar and second premolar, or palatally to
reinforce a trans-palatal arch (Figure 4.8).
Inter-arch mechanics.  Inter-maxillary elastics can
be used to apply traction between upper and lower
Figure 4.8  This orthognathic patient, who also has
hypodontia, has a number of mini bone screws or
Temporary Anchorage Devices (TADs) inserted in strategic
positions to provide absolute anchorage for tooth
movements that might otherwise be difficult to acheive.
(Courtesy of Dr Lucy Chung.)
Figure 4.9  (a) These check models, taken for a class II patient during pre-surgical orthodontics, revealed that the buccal
segment occlusion would be class II, due to incomplete incisor decompensation. (b) Inter-maxillary traction with class III
elastics, aimed at retroclining the lower incisors and proclining the uppers enabled class I buccal segments to be achieved
in the final result (c).
a)
c)
b)

68
Handbook of Orthognathic Treatment
The factors involved in deciding which technique
to employ include the following:
• The curve of Spee:  If this is severe, the amount
of posterior impaction of the maxilla required to
close the anterior open bite may be surgically
unachievable without resorting to a segmental
approach, particularly in cases where no down
graft of the anterior maxilla is required. Also,
orthodontic closure of the large posterior open
bites after surgery may be difficult.
• The risks associated with segmental surgery: 
Loss of periodontal bone support and gingival
attachment adjacent to the osteotomy cuts can
occur, with consequences for both dental health
and aesthetics. Occasionally, bone necrosis can
result from loss of the blood supply to one of the
segments. Because of these risks, some surgeons
may be reluctant to carry out segmental surgery
and will ask their orthodontist to deal with as
much of the arch levelling as possible, either before
or after surgery.
Lower anterior face height
In patients with a deep overbite and accentuated
curve of Spee, there are a number of ways of dealing
with the lower arch, depending on the change
required to the lower anterior face height and the
preferred approach of the clinicians:
1. Maintaining the curve of Spee, so as to leave the
vertical position of the lower incisors unchanged
throughout pre-surgical orthodontic treatment.
When placing stainless steel archwires it is neces­
sary to bend the curve into the wire in order to
avoid unwanted levelling. A downward move­
ment of the lower incisal edges and a correspond­
ing increase in lower anterior face height will then
accompany surgical advancement of the mandi­
ble. The surgery will create lateral open bites with
contact limited to the incisors and the terminal
molars (Figure 4.11). This is commonly known as
a ‘three-point landing’ and post-surgical ortho­
dontics is then required to close the open bites (see
below).
2. Orthodontically level the curve of Spee as fully as
possible prior to surgery. Theoretically, the disad­
vantages of this approach are that the lower inci­
sors will be intruded to some extent during the
levelling process. This, in turn, may limit the
increase in lower anterior face height that is
achieved through surgery. Also, the duration of
pre-surgical orthodontics may be increased because
of the additional time that arch levelling requires,
particularly in the presence of a deep overbite.
Figure 4.10  This patient is planned for segmental
maxillary surgery to level the severe curve of Spee. The
stepped archwire is aimed at preventing orthodontic
extrusion of the upper anterior teeth.
Limitations of orthodontic mechanics
There is a limit to the amount of levelling that ortho­
dontic appliances can achieve through tooth move­
ment alone, particularly in a non-growing patient,
and attempting orthodontic levelling of extreme
curves is unlikely to be successful. In the lower arch
this may be partly due to the fact that deep overbite
cases tend to be accompanied by heavy bite forces,
which resist the molar extrusion that normally con­
tributes to overbite reduction.
Where pre-surgical levelling of the lower arch is
required (see also ‘Lower anterior face height’ below)
the use of utility arch wires, which bypass the premo­
lars to apply an intrusive force to the incisors using
molar tip-back bends, may be effective during the
early stages of treatment. When continuous arch
mechanics are required, modern reverse-curve nickel-
titanium arch wires can be useful in maintaining a
prolonged levelling force along the length of the arch.
Stability
In anterior open bite cases with a significant curve in
the upper arch, orthodontic levelling will involve
extrusion of the incisors to some extent and there is
a risk that this may relapse after surgery. In such
cases, the alternatives to pre-surgical levelling are
two-fold:
1. Leave the curve unchanged during the pre-surgical
phase and then create posterior open bites through
posterior surgical impaction of the maxilla. These
open bites must then be closed post-surgically by
orthodontic extrusion of the molars.
2. Align the anterior and posterior segments at dif­
ferent levels using sectional orthodontic mechan­
ics, and then level the arch through segmental
surgery (Figure 4.10).

The role of orthodontics
69
lower arch will also be required, usually in the form
of contraction in class III cases. However, in class II,
division 2 cases the lower arch may be constricted
and a degree of pre-surgical expansion will be indi­
cated. The factors of relevance in the management of
transverse arch discrepancies are as follows:
Occlusion.  In some class III cases, where there is a
well established bilateral buccal segment cross-bite, it
may be very difficult to carry out significant expan­
sion of the maxillary arch before surgery due to the
locked buccal segment occlusion, even though the
amount of expansion required is within the scope of
orthodontic tooth movement. In such cases, it can
be easier to deal with the expansion post-surgically,
when the correction of the class III discrepancy will
have removed the occlusal interference.
Limitations of orthodontic mechanics.  Ortho­
dontic expansion, using a quad-helix appliance (or
equivalent) or stainless steel archwires, is achieved
mainly by tipping the teeth within the alveolar pro­
cesses and is usually limited to a few millimetres
between the molar cusps. If there is a significant
transverse skeletal discrepancy it is unlikely that
orthodontic expansion alone will be adequate to
produce satisfactory arch coordination. However, the
limit of orthodontic expansion for an individual
patient will depend on a number of factors, including
the degree of transverse compensation present in the
upper buccal segments. Where the molars are upright
over basal bone, considerable expansion will be pos­
sible, but if significant compensation is present,
further attempted expansion will produce excessive
flaring of the molars (Figure 4.12). In such cases, the
molar palatal cusps will tend to swing downwards
3. Use sectional mechanics to level the anterior and
posterior teeth separately and then surgically level
the arch using a segmental approach. This will
involve an anterior mandibular osteotomy to set
down the lower incisors (see Chapter 7). If a sub-
apical procedure is used, the mandibular advance­
ment surgery will produce little or no increase in
lower anterior face height. If a body osteotomy is
planned, then this will drop the chin level at the
same time as levelling the curve.
It is important to select the approach that is most
likely to achieve the desired effect on lower anterior
face height, whilst also keeping surgery as simple as
possible and orthodontic treatment duration to a
minimum.
4.2.4  Transverse tooth movements
Arch width discrepancies
Patients with antero-posterior and vertical jaw dis­
proportions will often have developed accompanying
transverse dental arch discrepancies; the most
common problem being a relatively narrow upper
arch. This may be a reflection of a genuinely narrow
maxilla, most commonly in class III malocclusions,
or may be secondary to a class II jaw discrepancy,
where the wider posterior maxillary arch occludes
with a narrow more anterior portion of the mandibu­
lar arch (see Chapter 2).
In planning pre-surgical orthodontics it is impor­
tant to assess the extent of any transverse problem
by hand-articulating the study casts in the anticipated
post-surgical class I occlusion. This gives a measure
of the amount of change in inter-molar width that
would be required to produce ideal arch coordination.
It may be that some alteration in the width of the
Figure 4.11  Class II case in which the lower curve of Spee
has been maintained throughout pre-surgical orthodontics
to produce a ‘three-point landing’ following surgery, with
the aim of increasing the lower anterior face height.
Figure 4.12  Cross-section of an upper study cast. The
blue lines illustrate the long axes of the roots and the
presence of buccal flaring.

70
Handbook of Orthognathic Treatment
The possible benefits of RME are:
1. A greater amount of maxillary arch expansion in
comparison to orthodontic archwires or quad-
helix, due to the skeletal effect of widening the
midline suture.
2. Less buccal tipping of the molars because the
expansion occurs more at a skeletal level.
3. Greater stability, as a result of bony infill of the
expanded mid-palatal suture.
The evidence for these benefits is equivocal and the
effects of RME, at a skeletal level, have been shown
to be variable and unpredictable, even in young
patients. However, it remains a straightforward and
relatively non-invasive technique for correcting
transverse maxillary deficiencies that are slightly
beyond the capability of conventional orthodontic
appliances.
Surgically Assisted Rapid Maxillary Expansion
(SARME).  Some patients have a severe transverse
deficiency of the maxilla that requires correction, but
is beyond the scope of conventional RME, or the
patient is not suitable for it. In such cases, there are
two possible options:
1. Surgical widening of the maxilla as part of a single
procedure (see Chapter 7).
2. SARME. This involves surgically dividing the mid-
palatal suture and the pterygo-maxillary sutures,
as well as making cuts in the lateral walls of the
maxillary sinuses, to remove as much of the bony
resistance to maxillary expansion as possible. A
palatal expansion appliance is then used in a
similar way to conventional RME (Figure 4.14). If
the appliance is placed at the time of surgery, it
can be a bone-borne design, engaging the palatal
vault for more direct force application. The theory
and cause occlusal interference, and the expansion is
likely to be unstable.
Where the transverse disproportion is severe, cor­
rection will be beyond the scope of simple orthodon­
tic tooth movement alone. An alternative method of
expansion may need to be considered, or the post-
surgical cross-bites accepted. If greater expansion of
the maxillary arch is desirable, then the various tech­
niques available must be carefully considered, taking
into account their risks and potential benefits.
Rapid maxillary expansion (RME).  Rapid Maxil­
lary Expansion (non-surgically assisted) is delivered
using a capped or banded appliance containing an
expansion screw (Figure 4.13), which the patient
turns each day over a period of a few weeks, with the
aim of separating the mid-palatal suture. Orthog­
nathic patients have usually completed their facial
growth and are therefore at least in their mid to late
teens. Conventionally, RME is recommended only in
patients up until the age of approximately 16 years
of age because the palatal sutures become less ame­
nable to separation beyond this age. However, the
literature does contain reports of RME in adults,
albeit with a tendency to an increase in complica­
tions, such as buccal gingival recession.
Whatever the patient’s age, it is essential that the
key signs of successful palatal separation are observed
early in the expansion process, that is, low resistance
to expansion and the appearance of a midline
diastema, as well as separation of the midline suture
on an occlusal radiograph, if one is routinely taken.
The prominence of the upper buccal segment roots
in the alveolar bone and the gingival attachment
levels should be closely monitored.
Figure 4.13  Capped design of RME appliance with silver
alloy base, cemented onto the surface of the teeth with
glass ionomer. The expansion screw has been fully
opened.
Figure 4.14  Surgically assisted RME (SARME) carried out
using a banded design of appliance. Note the dramatic
expansion acheived. (Courtesy of Dr David Morris.)

The role of orthodontics
71
the roots on either side of the cuts is important and
swapping the left and right canine brackets can assist
with this, converting distal to mesial root tip (see
Figure 9.5.2). Extraction of a premolar can be helpful
to avoid excessive proclination of the incisors and
improve surgical access.
4.2.6  Progress monitoring
It is essential that progress towards achieving arch
coordination is monitored throughout the course of
pre-surgical orthodontic treatment. The conven­
tional method of doing this is to take impressions for
check models that can be hand-articulated. In this
way, the occlusal fit can readily be assessed, including
any problems with tooth positioning and occlusal
interference. Check models should ideally first be
taken following initial alignment, so that subsequent
tooth adjustments can be planned in all three planes,
and then repeated again in rectangular wires until it
is felt that the aims of treatment have been accom­
plished. An up-to-date set of models should be avail­
able to take to the final planning appointment. In
addition to the occlusal goals, the inter-molar and
inter-canine width in the lower arch should be moni­
tored to ensure that the planned arch dimensions are
being achieved.
In cases where sectional orthodontic alignment is
being carried out prior to segmental surgery, the
check models will need to be sectioned to simulate
the surgical cuts, as well as any extractions planned
in theatre, to allow them to be articulated in the
correct occlusion. Intra-oral radiographs are also
helpful in assessing the proximity of the roots on
either side of the planned cuts.
It is also essential to monitor progress towards the
target overjet, or reverse overjet, which should have
been set as part of the pre-surgical orthodontic plan.
4.3  Peri-operative orthodontics
4.3.1  Fixed appliance preparation for
surgery
Once the aims of pre-surgical orthodontics have been
achieved and upper and lower rectangular stainless
steel archwires are in place (typically 0.019’ × 0.025’),
it is important to ensure that the teeth are prevented
from moving between final planning and surgery.
This is particularly important for the technologist,
who relies on the teeth being in a static position for
the accuracy of the model surgery and the fit of
the occlusal wafer(s). It is advisable to under-tie the
brackets in both arches to prevent any spaces from
is that widening of the maxilla will occur by dis­
traction osteo-genesis, allowing greater expansion
and improving stability.
There are potential advantages and disadvantages
of both techniques and the evidence in support of
greater stability for SARME is limited. The major
drawback of SARME is undoubtedly the need for
an additional surgical intervention under general
anaesthetic, in advance of the main orthognathic
procedure.
Surgical expansion of the maxilla.  Where
surgical maxillary widening is to be carried out,
pre-surgical orthodontics should ideally aim to
decompensate the upper buccal segments by tipping
them palatally, or at least avoid any further buccal
flaring of the teeth, which might lead to unfavoura­
ble dental relapse following surgery.
Dental centreline discrepancies
Any displacement of the dental centrelines should
ideally be corrected orthodontically prior to surgery.
However, this may be difficult in some cases where
the necessary tooth movements would require
extraction(s), which are otherwise unhelpful in
achieving the primary treatment goal of incisor
decompensation. For example, in a class III case, car­
rying out a unilateral lower arch extraction to correct
the lower centreline may lead to excessive retraction
of the incisors and a reduction in the reverse overjet.
It is therefore important to ensure that any limita­
tions of orthodontic centreline correction are
accounted for in the surgical plan (see also Chapter 3).
4.2.5  Orthodontic preparation for
segmental surgery
Where segmental surgery is planned, the orthodon­
tist can play an important role in reducing the risks
of iatrogenic damage in the following ways:
Mid-palatal split
Where mid-palatal widening is required it is advisable
to create a small midline diastema to ease access for
the surgeon’s osteotome. The roots of the central
incisors will also have to be adequately diverged,
although this should happen as a result of the mesial
crown tip built into the pre-adjusted edgewise
brackets.
Two-part maxilla and sub-apical osteotomies
Surgical cuts aimed at segmentally levelling the
dental arch will most commonly be sited distal to the
canines. Adequate separation and divergence of

72
Handbook of Orthognathic Treatment
lems, provided that there are teeth of sufficient
number and quality to support them. The authors
have used Bauermash® bondable arch bars for several
years and have found them to be an effective substi­
tute for conventional arch bars in selected cases.
Whilst bond failures in theatre sometimes occur, the
surgeon still has the option of using ligature wires if
necessary. If the patient has multiple porcelain resto­
rations that make bonding difficult, it is often advis­
able to use conventional arch bars.
4.3.3  The occlusal wafer
Delivering the planned occlusion
At the time of surgery, the new occlusion is dictated
by the final occlusal wafer and should exactly reflect
the occlusion agreed upon from the final check
models. In cases where good arch co-ordination and
inter-digitation have been achieved, the desired occlu­
sion should be obvious to the technologist. However,
in cases where it is less obvious, simply leaving the
technologist to select the ‘best fit’ of the teeth might
result in an erroneous wafer. It is therefore essential
that the surgeon, orthodontist and technologist agree
together on the occlusion they want, prior to the
fabrication of the wafer. It is personal preference how
this is done, but the final check models must be
transferred to the laboratory either clearly marked, or
located with some sort of bite register, in the correct
occlusion (see Chapter 5).
Having prescribed the correct occlusion to the
technologist, it is then essential that the clinical team
check that this has been accurately reproduced by the
model surgery on the articulator. If this protocol is
not diligently adhered to for every patient, it is inevi­
re-opening, and ensure that the archwires are passive
for at least six weeks, prior to the final planning
appointment.
Before the patient undergoes surgery, their appli­
ances should be checked for breakages and repaired
as required. It is also important to ensure that the
distal most attachments are secured to the archwire
to avoid the risk of them being lost into the surgical
sites. The routine use of bands, rather than bonds, on
terminal molars is advisable in this regard. If bonded
tubes are used, the archwire should be cinched back
behind them or they should be secured in some way
to the rest of the brackets.
4.3.2  Inter-maxillary fixation
For most patients, fixed orthodontic appliances
provide the means of applying inter-maxillary fixa­
tion (IMF) in theatre. This is required once for
single jaw osteotomy and twice for bi-maxillary
osteotomy, when an intermediate wafer is used to
locate the maxilla into its new position relative to the
mandible. There are two common methods of attach­
ing the elastics or wires to the fixed appliances in
theatre:
1. Orthodontic brackets with integral traction hooks.
2. Hooks attached to the archwire, either by crimp­
ing or soldering.
Brackets with integral hooks avoid the need to
place any attachments on the archwire prior to
surgery, saving chair-side time. However, such brack­
ets may impair oral hygiene during orthodontic treat­
ment and some clinicians argue that they risk
overloading the periodontal ligaments by delivering
the potentially heavy forces of the IMF directly to the
teeth, rather than to the more flexible archwire that
runs between them. The authors’ routine practice is
to place crimpable hooks on the archwires.
In patients who go to theatre without orthodontic
appliances in place, some other form of attachment
is needed on the teeth to facilitate IMF. Conventional
arch bars, ideally made in the laboratory, can be
attached using inter-dental ligature wires and are
very secure (Figure 4.15), but they have a number of
associated problems:
1. They must be applied in theatre because of the
need for ligature wires.
2. Ligature wires carry a risk of sharps injury.
3. Post-operative removal can be uncomfortable for
the patient.
4. They can cause trauma to the periodontal tissues.
An alternative solution is to use bondable arch bars
(Figure 4.21c), which largely eliminate these prob­
Figure 4.15  An example of conventional, pre-fabricated
arch bars, placed using trans-dental wire ligatures in
theatre.

The role of orthodontics
73
will have to be adjusted or fitted during surgery.
For example, in patients undergoing certain segmen­
tal procedures, it may be possible to replace the
sectional archwires, which have been in place
throughout pre-surgical orthodontics, with a con­
tinuous archwire. The benefit of this is that the
patient wakes up with a full thickness rectangular
archwire in place, which eliminates the need to carry
out post-operative realignment across the osteotomy
sites. However, even in the absence of a continuous
archwire, the final wafer can adequately locate the
segments and bracket alignment across the surgical
sites may not always be good enough to accept a
continuous archwire. The approach adopted is largely
down to the personal preferences of the clinicians
involved.
Where surgical widening of the maxilla has been
carried out, it may be beneficial for the orthodontist
to fit an ‘e-arch’ in theatre to assist retention (Figure
4.17). This reduces reliance on the wafer as an
expansion-retaining device and may allow it to be
discarded earlier after surgery.
table that some wafers will have to be remade, wasting
time and resources, and causing needless stress for all
concerned.
Patient and clinician acceptability
Surgical occlusal wafers are usually necessary in
theatre to ensure that the correct surgical and occlu­
sal goals are achieved, but there is divided opinion
regarding the need for the final wafer to be left in situ
post-operatively. It is the preference of the authors to
routinely leave the wafer in place for the first week
after surgery, but the choice of each team comes
down to personal preference. The following factors
are involved in the decision:
• It can be argued that once the final wafer has
served to correctly locate the mandible relative to
the maxilla in theatre, it is no longer required and
can be discarded. However, some clinicians may
find it reassuring to retain the wafer until at least
the first post-operative review on the combined
clinic so that they can see that the teeth are biting
into the planned occlusion.
• Patients commonly report that they find their
wafer uncomfortable and inconvenient post-
operatively. Oral hygiene is certainly impaired and
they are bulky to tolerate whilst recovering from
jaw surgery, when eating and drinking are already
challenging enough.
• Where surgical widening of the maxilla has been
carried out, this will have to be retained during the
immediate post-operative period. Leaving the wafer
in situ is one way of achieving this.
Where the preference is to retain the wafer post-
operatively, the patient must be informed that the
device will be in place when they wake up and they
should be given careful oral hygiene instruction.
Final wafers are conventionally retained in the
mouth using wire ligatures, which pass through holes
in the acrylic and around the orthodontic appliance.
The disadvantages of this design for the patient are
that the wafer is difficult and uncomfortable to
remove at the post-surgical review appointment. A
removable wafer that eliminates the use of wires is
therefore advantageous and a design routinely used
by the authors is shown in Figure 4.16. This saves
time in theatre, reduces the risk of sharps injury peri-
and post-operatively and allows easy removal and
re-insertion as required.
4.3.4  Orthodontic procedures in theatre
Whilst the orthodontist is seldom required in theatre,
there are certain situations in which an appliance
Figure 4.16  A removable design of final surgical wafer,
which is retained using elastomeric chain between the
hooks on the archwire and three ball-ended clasps
embedded in the acrylic.
Figure 4.17  An e-arch in place following surgery to retain
expansion of the maxillary arch. The arch is made in 1mm
hard stainless steel wire and is inserted into the head gear
tubes on the first molars bands.

74
Handbook of Orthognathic Treatment
occlusion should be checked with it out of the mouth.
Where the occlusion appears to be accurate, no active
adjustment of the jaw position(s) is required but it is
usually advisable to place medium weight inter-
maxillary elastics that support the jaw correction (i.e.
class II elastics for mandibular advancement) until
initial healing is complete.
Semi-rigid fixation
The screws or plates used in contemporary orthog­
nathic surgery provide only semi-rigid fixation and
there is a degree of malleability in the surgical sites
during the first six weeks or so post-operatively. This
has two implications. Firstly, the surgical movements
may be prone to early relapse under the influence of
the altered soft tissue environment. Secondly, it is
usually possible to manipulate the jaw positions to a
certain extent by applying traction to the orthodon­
tic appliances. Minor occlusal discrepancies are rela­
tively common and the immediate post-operative
period is a critical time during which close follow-up
on the combined clinic is essential in order to achieve
an optimal result.
Applying traction
In these cases it is important to start appropriately
directed and weighted elastic traction as early as pos­
sible to try to recover the planned occlusion (Figure
4.18). Protraction head-gear can also be useful in
helping to recover the maxillary position following
large advancements in severe class III cases. If early
adjustment of the jaw position(s) is required then the
patient may need several review appointments until
the planned occlusion is achieved and appears to be
stable. Heavy elastics will be required during the first
few weeks to achieve the desired adjustments, with
the weight reducing once the correct occlusion has
been achieved. If, after approximately six weeks, the
occlusion is still not correct it is unlikely that it can
be improved further at a skeletal level using elastic
traction.
4.4  Post-surgical orthodontics
The role of orthodontics following jaw surgery is to
achieve the final pre-planned occlusal and dental aes­
thetic result for the patient. Providing the surgical
plan has been followed, this stage should be relatively
short compared to the pre-treatment phase and is
carried out in three distinct phases:
• Post-surgical healing phase.
• Post-surgical tooth movement.
• Retention.
4.4.1  Post-surgical healing phase
In the immediate post-operative period, patients are
in a certain amount of discomfort and intra-oral
access will be limited for at least a few weeks, particu­
larly for those having undergone mandibular oste­
otomy. Post-surgical reviews should take place on the
combined clinic so that any complications, such as
trismus or early post-operative wound infection, can
be dealt with by the surgeon. During this time, oral
hygiene measures are particularly important and the
services of a hygienist are invaluable.
Following surgery, the bony segments will hope­
fully be located in their planned positions and large
occlusal discrepancies should be uncommon. How­
ever, in rare cases, where there is significant error in
the jaw position(s), the patient may have to be taken
back to theatre within the first week or two, for a
revision of the osteotomy.
Checking the occlusion
When the patient is reviewed one week post-surgery,
heavy inter-maxillary guiding elastics will typically
be in place, aimed at holding the teeth in the planned
occlusion. At this visit, the elastics should be removed
and the quality of the occlusion checked. If the wafer
is still in place then the lower teeth should be biting
fully into it without any sign of mandibular displace­
ment. If a removable wafer has been used then the
Figure 4.18  (a) Example of asymmetric inter-maxillary elastics aimed at correcting a centreline discrepancy in the
immediate post-operative period. (b) The corrected occlusion three weeks later.
a)
b)

The role of orthodontics
75
extrusion of the posterior teeth will be required to
close these (Figure 4.19). Whilst these tooth move­
ments are usually achievable, they can sometimes be
difficult, particularly in the more severe cases and a
high level of patient compliance is often required
with the wear of elastics.
Transverse
Active expansion of the maxillary or mandibular
dental arch may be required after surgery, where it
has not been possible to achieve this beforehand due
to occlusal locking. The tooth movements required
will usually be only a few millimetres and should be
achievable using archwires. Once good arch coordi­
nation has been established, stability should be pro­
moted by the inter-cuspation of the teeth as well as
the improved soft tissue environment, brought about
by the surgical jaw correction.
4.4.3  Retention
All orthognathic patients that have had adjunctive
orthodontic treatment require their dental alignment
and arch dimensions to be retained following appli­
ance removal. Whilst the surgical jaw correction may
have brought about the most significant change,
many patients are nevertheless still focused on the
appearance of their teeth and may be disappointed if
dental relapse occurs. Simple pressure-formed retain­
ers are usually adequate, but where surgical maxillary
expansion has been carried out a more rigid design
may be required. As with all orthodontic patients, the
length of time for which retainers will need to worn
is difficult to predict and contemporary thinking is
to encourage wear for as long as ideal alignment is
desired. Where appropriate, bonded retainer wires
allow reduced reliance on removable retainers to
maintain incisor alignment. However, it must be
remembered that they do not maintain transverse
arch dimensions particularly well and patients that
have had significant maxillary expansion carried out
4.4.2  Post-surgical tooth movement
By the time the initial healing stage is over, it should
be possible to gain sufficient intra-oral access to carry
out any necessary post-surgical orthodontic tooth
movement. In the majority of cases, where there are
already fixed appliances in place, the surgical arch­
wires should be removed and any breakages repaired.
In cases where post-surgical orthodontics only is
planned, the appliances should be placed at this stage.
It is convenient to consider the post-surgical tooth
movements required in all three planes of space.
Antero-posterior
Although the planned amount of incisor decompen­
sation is usually achieved before surgery, there are
cases where this can be hampered by the unfavour­
able pre-surgical soft tissue environment, particularly
in very severe malocclusions. After surgery, this
should be greatly improved and it may be possible to
achieve further tooth movement in the desired
direction.
Any residual space closure within the dental arches
is also carried out at this time, but care must be taken
to manage the anchorage balance such that the inci­
sors and molars finish up in the correct occlusion.
This may, once again, require the use of inter-
maxillary elastics, but with lighter forces aimed at
assisting tooth movement rather than producing
skeletal change.
Vertical
As mentioned previously, where a curve of Spee is
maintained throughout pre-surgical orthodontics,
there will be a need to level this after surgery. Where
an anterior open bite has been closed by posterior
maxillary impaction, there will be bilateral posterior
open bites resulting from the upper arch curve and
extrusion of the upper posterior teeth will be required.
In the case of a three-point landing, the lower arch
curve will have resulted in lateral open bites and
Figure 4.19  (a) Lateral open bites in a class II ‘three-point landing’ case, post-surgery. (b) The lateral open bites have
been closed through combination vertical elastic traction and repositioning of attachments.
a)
b)

76
Handbook of Orthognathic Treatment
jaw discrepancy prior to decompensation reduces this
resistance by normalising the soft tissue environment
of the teeth.
Treatment duration
By limiting orthodontic treatment to the post-
surgical phase, the overall length of treatment should
be reduced, although of course patients suitable for
this approach are likely to be those requiring fairly
straightforward orthodontic alignment. This is clear­
ly more convenient for the patient and reduces
the risks of appliance-induced iatrogenic damage.
For the patient illustrated in Figure 4.21, fixed appli­
ances were in place for only 10 months, as opposed
to possibly 18–20 months, had she been treated
conventionally.
4.5.2  Disadvantages
Planning the occlusion
A key disadvantage of leaving orthodontic treatment
until after surgery is that the occlusion produced must
allow for any desired post-surgical adjustment of the
incisor inclinations. The final wafer position must
therefore be carefully judged to allow the post-surgical
orthodontics to achieve as close to an ideal occlusal
result as possible. This is not always straightforward
since the precise way in which the incisors and molars
will move within the dental arches after surgery can
be difficult to predict and the orthodontist will often
have to rely on good patient compliance with inter-
maxillary elastics to control anchorage.
Patient commitment
One of the benefits of pre-surgical orthodontics is
that the patient has several months over which to
think about the prospect of jaw surgery and in some
cases they may change their mind and opt for a
compromised result involving orthodontics alone.
Where this phase is eliminated the patient may not
always have an adequate chance to adjust to the idea
of surgery and have second thoughts much closer to
the operation date, causing stress and inconvenience
for all concerned.
This, of course, also applies to patients who have
surgery alone without any orthodontics. The
informed consent process is therefore particularly
important for patients going straight to surgery and
a ‘cooling off’ period is to be encouraged, where the
patient is given some additional time to digest the
information given to them and ask further questions.
Having the input of a psychologist at key stages
should be aware that they may always have to wear
some form of upper arch retainer.
4.5  Surgery before orthodontics
Although a large proportion of orthognathic patients
will undergo both pre- and post-surgical orthodon­
tics, there are some patients for whom carrying out
the surgery first and the orthodontics afterwards is
an option. It is important that a reasonable occlusion
can be achieved through surgery alone but, assuming
this is the case, there are a number of advantages and
disadvantages to be considered.
4.5.1  Advantages
Facial aesthetics
In many cases, pre-surgical orthodontics has the sig­
nificant drawback that it makes the patient look
worse than before they started treatment. This is par­
ticularly true for class III patients, where decompen­
sating the incisors accentuates the jaw discrepancy
(Figure 4.20). Whilst some patients may be more con­
cerned by this than others, carrying out the surgical
jaw correction first has the advantage of eliminating
this phase and instead delivering the major improve­
ment in facial appearance at the start of treatment.
Resistance to tooth movement
As previously mentioned, decompensating incisors
prior to surgery often involves moving them against
the resistance of the lips and tongue. Correcting the
Figure 4.20  A class III patient (a) before and (b) after
pre-surgical orthodontics, showing the detrimental effect
on the profile of lower incisor decompensation.
a)
b)

The role of orthodontics
77
4.6  Surgery without orthodontics
Whilst the majority of patients planned for orthog­
nathic surgery will benefit from orthodontic treat­
ment as part of their management, it is not always
necessary and its risks and benefits must be carefully
assessed in each individual case. Reasons why a
patient may undergo surgery without any adjunctive
orthodontic treatment include the following:
• The predicted post-surgical occlusion and arch coor­
dination are satisfactory, to the point where ortho­
dontics will not significantly improve the situation.
• The antero-posterior position of the incisors is
such that the desired magnitude of surgical
throughout the patient journey is invaluable in this
regard.
Similarly, patients who are primarily focused on
the change in facial appearance that surgery will
deliver for them may agree to post-surgical orthodon­
tics at the planning stage, but once they have seen
the outcome of surgery they may decline to go
through with it. Whilst in most cases this will not be
disastrous, it may mean that the patient ends up with
a sub-optimal occlusion and less than ideal dental
aesthetics. Care should be taken, therefore, to ensure
that the patient understands that orthodontics will
be an integral part of the overall treatment plan
during the consent process.
Figure 4.21  (a, b) Class III patient with mid-face deficiency and mandibular prognathism. (c) Bi-maxillary osteotomy
(maxillary advancement, malar augmentation and mandibular setback) was carried out first. Because no fixed
appliances were in place during surgery, Bauermash® bondable arch bars were used for IMF and for running guiding
elastics in the immediate post-surgical period. (d) Following initial healing, upper and lower fixed appliances were
placed, with the aid of class III elastics to control the incisor relationship. (e, f) Satisfactory occlusion and facial aesthetics
were achieved.
a)
d)
e)
c)
f)
b)

78
Handbook of Orthognathic Treatment
most common in upper incisors and more likely to
occur with large tipping or torquing movements,
especially where the apices are brought into contact
with the bony cortical plates. Short, blunt roots prior
to treatment are a further risk factor.
4.7.2  Loss of periodontal support
Orthognathic patients frequently require dental arch
expansion, both in the antero-posterior and trans­
verse directions. In non-growing patients, moving
teeth into their cortical plates carries a risk of dehis­
cence and this can result in gingival recession. This
is probably most commonly associated with lower
incisors following proclination in class III cases
(Figure 4.23), but proclining upper incisor in class II,
division 2 cases can cause similar problems. It can
also occur as a result of transverse maxillary arch
expansion, particularly where there is pre-existing
recession.
In patients who have a history of periodontal
disease and have lost horizontal bone support, there
will be a risk of this progressing as a result of ortho­
dontic tooth movement. It is therefore important to
ensure that active disease is controlled prior to the
start of treatment and assessment by a periodontolo­
gist may be required.
4.8  Summary
• Most orthognathic patients have developed incisor
compensation as a result of their disproportionate
jaw growth and pre-surgical orthodontics aims to
reverse this in preparation for surgery through the
process of decompensation.
correction can be achieved without the need for
decompensation.
• The patient’s dentition is incomplete such that
they are not suitable for fixed appliances, but a
reasonable, functional occlusion can still be
achieved.
4.7  Complications of orthodontic
treatment
Fixed orthodontic appliances carry a number of risks,
which the patient must be made aware of as part of
the consent process. These fall into the following
categories:
4.7.1  Iatrogenic tooth damage
Decalcification
The risk of enamel decalcification associated with
fixed appliances should not generally be high for
orthognathic patients because they are mainly adults.
However, it can still occur (Figure 4.22), particularly
where treatment is protracted and there are problems
with oral hygiene or diet and a high previous caries
experience. Frequent hygienist support is invaluable
in minimising this risk.
Root resorption
A small amount of root resorption is inevitable as a
result of moving teeth in most patients but it is
usually clinically insignificant. Occasionally, one or
more roots may shorten to a much greater extent
than usual and leave the tooth slightly mobile at the
end of treatment. Whilst this is unpredictable, it is
Figure 4.22  Patient with severe enamel decalcification
marks following completion of combined surgical
orthodontic treatment. The overall duration of treatment
was protracted due to several failed appointments and
the patient struggled with oral hygiene and diet control.
Figure 4.23  Labial gingival recession affecting a lower
central incisor as a result of pre-surgical decompensation
in a class III patient.

The role of orthodontics
79
• Narrowness of the maxillary arch can be corrected
using different expansion techniques, depending
on its severity. These include tipping of the teeth
orthodontically,
RME,
SARME
and
surgical
widening.
• In some cases, where adequate maxillary expansion
will be difficult to achieve, a bilateral buccal
segment cross-bite may have to be accepted.
• Where necessary, it is usually possible to manipu­
late the surgical segments using inter-maxillary
elastics for a period of approximately six weeks
post-operatively in order to correct occlusal
discrepancies.
• The clinician must be aware of the potential for
iatrogenic damage with fixed appliances and good
oral health should be a pre-requisite to combined
surgical orthodontic treatment.
4.9  Recommended further reading
Proffit W.R., Fields H.W., Sarver D.M. (2013) Contemporary
Orthodontics, Section IV, 5th Edition, Elsevier.
• The amount of incisor decompensation carried out
dictates the size of the surgical jaw movements and
may influence whether surgery will involve one or
both jaws.
• Decompensation may be limited by the degree of
crowding or spacing in the dental arches, the
quality of the periodontal tissues and the resistance
of the soft tissues.
• Incisor decompensation can be controlled using
the appliance prescription, the extraction pattern
and torque adjustments to the archwires.
• Anchorage can be managed using inter-maxillary
elastics, trans-palatal arches and mini bone screws.
• Patients with anterior open bites often have accen­
tuated upper curves of Spee. If levelling is beyond
the scope of orthodontics then segmental surgery,
with sectional orthodontic mechanics, may be
required.
• Class II patients with deep bites tend to have accen­
tuated lower curves of Spee. Where a mandibular
advancement is planned it will often be desirable to
maintain this curve during pre-surgical orthodon­
tics, with the aim of increasing the lower anterior
face height. This is termed a ‘three-point landing’.

Intended learning outcomes
By the end of this chapter the reader should:
• Have a working understanding of face bow
recordings and their anatomical importance, the
use of articulated dental casts for surgical
prediction including measurement of movements,
construction of occlusal re-positioning wafers and
the use of 3D models in surgery planning.
Orthognathic technical procedures
5
Chapter overview
Intended learning outcomes, 80
5.1
Introduction, 80
5.2
Clinical assessment, 81
5.2.1 Patient planning sheet, 81
5.2.2 Master impressions, 81
5.2.3 Occlusal registration, 81
5.2.4 Face bow recording, 81
5.3
Articulator and face bow selection,
81
5.3.1 Plain line articulator (simple hinge), 83
5.3.2 Semi-adjustable articulators and face bow
recordings, 83
5.4
Face bow recordings, 83
5.5
Face bow points and planes of
reference, 84
5.5.1 Auricular average value face bow, 84
5.5.2 Condylar face bow, 84
5.6
Errors in face bow registrations used for
orthognathic model surgery, 85
5.7
Face bow with orbital pin replaced with
a bull’s eye spirit level, 87
5.8
Orthognathic articulator and face bow,
87
5.8.1 Face bow, 87
5.8.2 Articulator, 88
5.9
Preparing the casts for articulation, 88
5.9.1 Articulating the casts, 89
5.9.2 Marking out the casts, 89
5.9.3 Marking and measuring the casts for vertical
movements, 90
5.9.4 Marking and measuring the casts for antero-
posterior movements, 90
5.9.5 Repositioning the casts, 90
5.9.6 Occlusal re-positioning wafer, 91
5.10 Recent advances in model surgery, 92
5.11  Suggested further reading, 93
and soft tissues to reproduce the planned prescribed
surgery on anatomically positioned dental casts in
three dimensions. This procedure will allow the surgi­
cal team the opportunity to examine the predicted
surgical outcome and allow re evaluation of the plan
should this be required. Perhaps the most important
aspect of the model surgery is the construction of
intra operative occlusal wafers in final and intermedi­
ate positions used to reposition the upper and lower
jaws at the time of surgery.
The opportunity to see the patient by the technolo­
gist responsible for the model surgery is essential and
invaluable. The technologist can visualise the degree
of correction required to treat the patient, this can
include the amount of maxillary tooth show, whether
there is an occlusal cant present or indeed any facial
asymmetry which needs to be considered when for­
mulating the treatment plan.
80
5.1  Introduction
The role of the maxillofacial technologist as a member
of the team treating patients presenting at a dento-
facial deformity clinic can be easily defined. The tech­
nologist will use clinical measurements of the hard
Handbook of Orthognathic Treatment: A team approach, First Edition. Ashraf Ayoub, Balvinder Khambay, Philip Benington,
Lyndia Green, Khursheed Moos, and Fraser Walker.
© 2014 John Wiley & Sons, Ltd. Published 2014 by John Wiley & Sons, Ltd.

Orthognathic technical procedures
81
attachments often tear the impression material or
separate it from the impression tray rendering it
useless, under these circumstances the impression
must be repeated until a suitable one is taken. The
best types of impression tray are the fine perforated
metal trays or the disposable orthodontic trays spe­
cifically designed for orthodontic impressions. The
impression can be checked by turning it over to the
tray side to ensure it is firmly attached, if not it must
be rejected. The technologist will invest two or three
working days on the pre-op master models obtained
from the impressions so must be satisfied they are fit
for purpose.
Once the plan has been formulated and agreed
with the patient it will be necessary to formalise the
model surgery with some anatomically accurate
models and clinical measurements of the patient.
5.2  Clinical assessment
At the surgery planning appointment the following
must be obtained in order for an anatomical model
surgery plan to be carried out.
1. Planning sheet (Figure 5.1).
2. Master impressions.
3. Occlusal registration.
4. Face bow recording (if required).
5. Proposed surgical plan.
5.2.1  Patient planning sheet
The first stage in this process is to record the patient’s
soft tissue and dental measurements on a treatment
planning sheet. This will ensure the patient’s indi­
vidual details are accurately recorded to allow model
surgery to be carried out. Details in addition to those
previously mentioned include the dental centre lines,
chin point, freeway space, overjet and overbite and
are amongst the relevant items of information to be
recorded; a clinic during which several new patients
have been seen may be vivid in one’s memory on the
day, however, this will be less so a few days later
and the planning sheet should avoid confusion in
this regard. Additional information should include
patient contact details in case it is necessary to recall
them for further clinical assessment.
5.2.2  Master impressions
The technologist must be given the opportunity to
examine the final impressions for quality control and
must ensure the impressions are not loose in the tray.
All present teeth must be included, often wisdom
teeth can be missed or be only partially present in
the impression. These teeth may be in occlusion and
their omission may well cause problems when
re-positioning the jaws during surgery therefore care
at the impression stage is essential. The selection of
impression material is a question of operator choice
but it must provide accurate models. If circumstances
are such that the impressions cannot be cast quickly
a dimensionally stable material such as a rubber
based product must be used. The choice of impres­
sion tray is also critical and this must be capable of
withstanding the difficulties associated with the
removal of the impression when orthodontic attach­
ments are present on the teeth. The orthodontic
TIP:  Commonly the impressions will be laid on
a bench prior to casting. If the impressions are
allowed to rest on the heel this can cause dis­
lodging and distortion from the tray. A simple
solution is to rest the impressions on a piece of
wood or spatula handle which will avoid this
problem (Figure 5.2).
5.2.3  Occlusal registration
A registration of the patient’s occlusion should be
taken at the clinical appointment and similarly
should be carefully checked for accuracy. Once again
the selection of registration material is operator
choice. In addition to wax there is a large selection
of silicone based materials formulated for bite regis­
tration purposes available. It is worth noting the
reason for most discrepancies occurring between the
prediction planning and the model surgery, these
tend to be as a result of inaccurate occlusal registra­
tions so it is always worth taking the time to double
check the accuracy of the bite record.
5.2.4  Face bow recording
Finally a face bow registration should be taken if
required. This must be taken by an experienced
member of the team used to the procedures of face
bow recordings. The face bow is the foundation of
model surgery and inaccuracy at this stage may be
transferred to the patient’s intra-operative position­
ing wafer and subsequently it will have a detrimental
effect on the patient’s post-operative outcome. The
face bow recording procedure is described later in this
chapter.
5.3  Articulator and face bow selection
Orthognathic model surgery plays an important part
in the diagnosis and treatment of the dento-facial

82
Handbook of Orthognathic Treatment
Figure 5.1  Patient planning sheet.
NAME
NUMBER
Tel:
Age
Orthodontics Yes/No
Resting lip line to upper incisal edge (tooth visible)
Smiling lip line to upper incisal edge
Tooth - lower midline normal Yes/No
Tooth - upper midline normal Yes/No
Chin point central Yes/No
CONSULTANT
mms
mms
mms
mms
Left
Right
mms
mms
mms
Left
Right
mms
mms (incisor-incisor)
AOB
mms
mms/overjet
Overbite
Left
Right
mms
Chin
Models
Model Surgery
Model Surgery Indicates
Date of Pre-operative visit
Date of Operation
Signed
Date
Mandibular Model
Malar
Facebow
Genioplasty
Right
Left
Occlusal cant
Photo Prediction Plan:
Maxilla
Mandible
Level of Procedure Le Fort I. II. III
Segmental Yes/No
Yes/No
Yes/No
Yes/No
Yes/No
Date Required
Yes/No
Please fill in mark on models
Maxilla Anterior 1/1
Molar 6/6
Mandible
Yes/No
Yes/No
Specify type of procedure:
Specify
mms
Freeway space
deformity patient. There are many differing tech­
niques and methods of model surgery used by the
maxillofacial technologist within the laboratory
environment, many of which are employed as a
result of a particular departmental or operator prefer­
ence or are simply historically employed techniques
handed down from technologist to technologist. In
today’s practice evidence based techniques are
required to comply with health care policies. The
inherent problems with face bow registrations and

Orthognathic technical procedures
83
with a face bow recording. This recording is used to
orientate the dental casts of the patient on the dental
articulator allowing pre surgical diagnostic assess­
ments to be made.
The principles of usage of a face bow recording and
a semi adjustable articulator must be considered. The
prosthetic application for which these instruments
were designed must be re-evaluated as the anatomical
points of interest for the correction of a dento-facial
deformity differ significantly from those required for
prosthetic dental restorations. The face bow record­
ing must accurately position the maxillae in relation
to the base of the skull. In addition the maxillary
occlusal plane angle must be recorded precisely. Fail­
ure to record either of these with optimal precision
will render model surgery inaccurate. It is important
to remember that any inaccuracies incorporated into
the model surgery will be transferred to the intra-
operative repositioning splints and subsequently to
the patient at the time of surgery producing a com­
promised surgical outcome.
5.4  Face bow recordings
Face bows commonly used for orthognathic model
surgery will record the A.P. dimension of the patient
with acceptable accuracy, however, most tend to
overestimate the maxillary occlusal plane angle with
dire consequences. These consequences will be dis­
cussed later in this chapter.
Firstly the available face bows should be considered
to allow appropriate selection. The face bow is devel­
oped for individual articulators and as a rule should
not be interchanged. Therefore it would not be wise
to use for example a Dentatus face bow with a Hanau
articulator selection have been well documented in
the literature. Before considering the selection of the
appropriate articulator for a given procedure it should
be noted from the outset that the instruments in use
today are dental in origin and were not designed for
orthognathic model surgery, thus criticism of their
inadequacy is inappropriate and the technologist
must be prepared to modify techniques to compen­
sate for their inaccuracy.
5.3.1  Plain line articulator (simple hinge)
The simple hinge articulator or plain line articulator
as it is more commonly known is the most basic
dental articulator capable of only opening and closing
from a fixed hinged axis point. Dental casts are
mounted between the top and bottom arm in an
arbitrary position. There is no anatomical orientation
to the skull with the exception of the occlusal rela­
tionship of the upper and lower teeth.
This can be used successfully for some single jaw
osteotomies and segmental procedures typical appli­
cations would include:
1. Le Fort I Maxillary osteotomies without height
changes (impaction or down grafting).
2. Mandibular advancements.
3. Mandibular setbacks.
4. Sub apical segmental osteotomies.
5.3.2  Semi-adjustable articulators and face
bow recordings
For patients requiring surgery on both the upper and
lower jaws (bi-maxillary procedures) to correct a
facial deformity or for maxillary surgery requiring
height changes, the use of a semi-adjustable articula­
tor is essential (Figure 5.3). This principle applies to
all bi-maxillary procedures with no exceptions. The
semi-adjustable articulator is used in conjunction
Figure 5.2  Impressions resting on a support.
Figure 5.3  Range of popular semi-adjustable articulators:
left to right – Denar, KaVo, SAM, Hanau, Dentatus.

84
Handbook of Orthognathic Treatment
found in the arbitrary position of 13 millimetres
anterior to the external auditory meatus. This assump­
tion may be reasonable for patients with a symmet­
rical deformity. However, it is not appropriate for
patients with craniofacial deformities such as hemi­
facial microsomia where the position of the condylar
head will not be in a predictable position. A further
disadvantage incorporated into some auricular face
bows is the design of the bite registration fork. This
fork is part of a removable jig which is detached from
the face bow after bite registration has been com­
pleted. This allows the operator to have one face bow
with several registration jigs providing a cost efficient
system in comparison to the condylar type of face
bow which does not have removable components.
The literature has many evaluations which show this
to be the least accurate method of maxillary cast
orientation due mainly to the separation of the bite
registration fork from the face bow, its instability and
its subsequent transfer to the articulator for maxillary
cast mounting.
5.5.2  Condylar face bow
The condylar face bow (Figure 5.4b) requires the
operator to identify the centre of the condylar head.
This operation is carried out by palpating the soft
tissue covering the condylar head and marking the
centre point on the patient’s skin with a pen.
With the condylar heads identified the face bow is
offered up to the patient and the condylar rods are
independently adjusted (Figure 5.5) and the face bow
is positioned with the condylar rods recording the
same measurement on each side of the patient: (1)
The bite fork is tightened on the face bow, (2) lastly
the orbital pointer is placed over orbitale and (3) is
similarly tightened.
articulator regardless of the fact that Dentatus face
bows fit the Hanau articulator and vice versa. Ana­
tomical reference points differ depending on the
manufacturer, but for the face bow to be of use for
orthognathic model surgery it must record three
points or planes of reference.
5.5  Face bow points and planes of
reference
1. Maxillary occlusal plane.
2. External auditory meati or the condylar heads.
3. Orbitale, Campers plane or Nasion.
There are two commonly used types of face bow
available for mounting casts on the semi-adjustable
articulator. These are the auricular average value face
bow and the condylar average value face bow.
5.5.1  Auricular average value face bow
The auricular face bow uses the external auditory
meati as the posterior location. The maxillary denti­
tion recorded on the bite fork which is attached to
the face bow frame is the second recorded anatomical
plane (Figure 5.4a). The third point of reference will
vary depending on the manufacturer’s preference.
This may be any of the points listed previously as face
bow points of reference item 3. The auricular face
bow finds favour as it is considered to give reproduc­
ible results due to the ease of locating the external
auditory meati. It is, however, hard to see the rele­
vance of the auditory meati in relation to mandibular
deformity correction or maxillary cast positioning on
the articulator. This type of face bow makes the
assumption that the head of the condyle will be
Figure 5.4  Two main types of face bow: (a) Denar slidematic and (b) Dentatus.
a)
b)

Orthognathic technical procedures
85
Figure 5.5  Patient with face bow recording.
over-estimate the maxillary occlusal plane angle
which will produce unseen and unwanted move­
ments from the model surgery prediction. This
finding shows the errors which would be incorpo­
rated in the model surgery should the maxillary
occlusal plane angle not be recorded accurately.
Figure 5.8 shows a lateral cephalogram placed in
the correct anatomical position of the maxilla in rela­
tion to the articulator. The vertical line is a datum
line with no anatomical significance other than
being positioned in relation to the anterior position
of the upper central teeth.
Figure 5.9 shows the maxillary cast mounted to
the articulator using the face bow according to the
manufacturer’s instructions. At this stage the increase
of the maxillary occlusal plane angle is obvious.
For the purpose of this illustration we have assumed
the maxilla has been impacted by 6mm with no
advancement.
Figure 5.10 shows the maxillary cast with 6mm
impaction but with the maxillary cast positioned
All the joints on the face bow are tightened to
prevent movement when using the face bow to
mount the maxillary dental cast on the articulator.
This type of face bow with modifications would be
the author’s choice as it records anatomical points of
interest which would be relevant for the process of
jaw deformity correction.
Figure 5.6  Arrow showing bite fork resting on the bench.
Figure 5.7  Face bow hung on a hook to prevent damage.
TIP:  The face bow registration should always
be hung on a hook (Figure 5.7) or similar method
of storage. If left lying around or resting on
anatomical pointers or the wax bite fork (Figure
5.6) the face bow could be rendered inaccurate
and this would not be readily visible at the
time of mounting the model.
5.6  Errors in face bow registrations
used for orthognathic model surgery
The previously described methods of face bow record­
ing are recommended by the instrument manufactur­
ers and are commonly used for mounting casts for
model surgery. However, they have inherent anatom­
ical design faults which will hinder accurate model
surgery prediction. These errors have been well docu­
mented in the literature over many years and many
suggestions for modifying the cast mounting tech­
nique have been made. The anatomical errors become
more serious when the upper and lower casts are
separated from the mounting plaster on the articula­
tor and are subsequently repositioned to simulate the
new position of the jaws. Once again it must be
remembered this instrument is being adapted for a
purpose for which it was not designed or intended.
The face bow systems used for mounting the maxil­
lary cast on to semi adjustable articulators tend to

86
Handbook of Orthognathic Treatment
with an increased occlusal plane angle. As previously
mentioned, these illustrated errors would be trans­
ferred to the intra-operative wafers and subsequently
to the patient.
Operational errors can be greatly reduced by aban­
doning anatomical landmark indicators such as
orbital pointers and nasion rests which are com­
monly found on commercial instruments and substi­
tuting these for a bull’s eye spirit level (Figure 5.11).
By securing a spirit level to the face bow it is then
possible to record the patient’s natural head position
and thus transfer the casts to the articulator with
greatly increased accuracy.
over the superimposed lateral cephalogram which
represents the patient’s true maxillary occlusal plane
angle. This reproduces the actual anatomically correct
position of the patient’s maxilla. The illustration
shows the amount of maxillary advancement ante­
rior of the vertical red line (arrowed) which is unseen
on the model surgery. This error is entirely as a result
of mounting the maxillary cast on the articulator
Figure 5.8  Patient’s ceph anatomically positioned on the
articulator.
Figure 5.9  Patient’s maxillary cast mounted according to
manufacturer’s instructions.
Figure 5.10  Maxillary cast showing unwanted
advancement.
Figure 5.11  Face bow with orbital pin replaced with a
bulls eye spirit level.