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CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
it has approximately 90% penetrance, and it is variably
expressed (see Fig. 4-17). Manifestations of the syndrome
outside of the oral and facial regions are unusual. Generally,
the pits are characterized as depressions that are observed
on the vermilion border of the lower lip; they are usually
bilateral and symmetrically placed, although an asymmetri­
cal pit or single central pit may occur. Roughly 33% of
patients with van der Woude syndrome have pits without
clefting, 33% have pits with cleft lip and palate, and 33%
have lip pits with isolated cleft palate or submucous cleft
palate. Approximately 10% of those individuals with van
der Woude syndrome do not exhibit lip pits.
Stickler Syndrome
In 1967, Stickler and Pugh were the first to describe a
series of patients who had a combination of eye findings,
hearing loss, isolated cleft palate, a Marfanoid habitus, and
long-bone changes.1 It is now known that Stickler syndrome
is associated with basic defects in collagen. These colla­
genopathies include mutations on type II collagen and
mutations in type XI collagen.25 The inheritance pattern
with this syndrome is autosomal dominant with variable
expressivity. Cohen and others have reviewed the relation­
ship between high myopia and clefting of the secondary
palate and the other features of Stickler syndrome.19 High
myopia (i.e., 8 to 18 diopters) is found in 75% of patients
by the time they are 5 years old. The eye findings are
progressive, with vitreous and chorioretinal degeneration
and retinal detachment observed in 70% of patients by
the time they are 20 years old. Additional eye findings
include astigmatism, cataracts, strabismus, and glaucoma.
Individuals with Stickler syndrome may manifest any or
all of a range of craniofacial findings, including mild to
moderate midface hypoplasia, shallow orbits with eye pro­
ptosis, epicanthal folds, a flat nasal bridge, and submucous
or full clefting of the secondary palate. Some affected indi­
viduals will have progressive degeneration of the dental
roots and the associated periodontium. This is primarily
due to the inborn error in collagen production, but it may
be exacerbated by malocclusion (secondary trauma) and
orthodontic manipulations (see Fig. 4-18). Progressive
neurosensory high-tone hearing loss has been reported in
80% of patients. Some patients have a Marfanoid body
habitus, whereas others have short stature. There may be
progressive early joint degeneration by the mid-adult years.
Any newborn who is found to have Robin sequence should
undergo an initial genetic and ophthalmologic assessment
to rule out Stickler syndrome.
Robin Sequence
Robin sequence is commonly defined as cleft palate, micro­
gnathia, and glossoptosis (see Fig. 4-19). This sequence of
events can occur as a result of a variety of etiologic and
pathogenetic conditions, and it involves a wide spectrum of
phenotypes. The distinction must be made between a mal­
formed mandible (micrognathia) and a deformed mandible
that is simply retrognathic. The malformed mandible (i.e.,
Treacher Collins syndrome) may also be missing parts or
sections of the jaw (i.e., Kaban types IIB and III) and
cannot be expected to “grow out” and self-correct. This is
different from a deformed mandible (i.e., retrognathic at
birth) caused by fetal malpositioning, which can be expected
to “grow out” and become relatively normal. The newborn’s
respiratory compromise that occurs with Robin sequence
will vary according to the child’s physical findings, and
treatment should proceed accordingly. For example, with
spondyloepiphyseal dysplasia congenita, the causes of respi­
ratory compromise include a small and mechanically abnor­
mal chest, tracheobronchial malacia, and central apnea as a
result of cervical or medullary compression caused by cervi­
cal instability.47 This will require a different level of airway
management as compared with an isolated retrognathic
mandible, which is simply deformed as a result of intrauter­
ine compression. If the deformed (retrognathic) mandible
is present at birth, it is expected to “catch up” during growth
and basically to self-correct. For these infants, mandibular
osteotomies with advancement carried out during child­
hood should be avoided.
Achondroplasia
Achondroplasia is the most common condition associated
with severe disproportionate short stature.22 The cause of
this condition is the failure during development of the
primary growth cartilages of the limbs and the cranial base.
This results in short arms and legs as well as a characteristic
midface deficiency or deformity that is most visually notable
at the nasofrontal process.
Most affected individuals do well but attain a final height
of only approximately 4 feet. The condition is known to be
caused by mutations on the FGFR3 (fibroblast growth
factor receptor 3) gene.22 Eighty percent of reported cases
are sporadic, whereas 20% are familial. Although craniosyn­
ostosis is not a typical feature, three cases with craniosyn­
ostosis have been reported.
Premature Suture Closure of the Cranial Vault
and Skull Base
The flat bones of the cranial vault develop from mesenchy­
mal condensations over the developing brain (see Fig. 4-1).
These bones grow primarily via the apposition of bone at
their edges. The regions in which the cranial bony edges
collide are called sutures. In addition to appositional growth
at the edges (i.e., suture growth), cranial vault development
also occurs through the process of remodeling (i.e., resorp­
tion and deposition).17 Continued separation of the sutures
during the process of the apposition of bone at the edges is
also important to the normal growth of the bones of the
cranial base and the midface.
Synostosis is a condition of premature fusion (i.e., the
arrest of appositional growth at the bone edges) that occurs
before the associated visceral structures (e.g., brain, eyes)
complete growth.17 When this happens, there is distortion

92
SECTION 1  Basic Principles and Concepts
B1
B2
©Elsevier Inc.
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icic
icicic Su
Su
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A
• Figure 4-20  A child born with metopic synostosis that resulted in trigonocephaly. He underwent anterior cranial vault and three-quarter orbital
osteotomies with reshaping when he was 10 months old. A, Facial and computed tomography scan views before surgery. B, Illustrations of the
craniofacial skeleton in a child with metopic synostosis that resulted in trigonocephaly before and after anterior cranial vault and three-quarter orbital
osteotomies. C, Bird’s-eye view of removed orbital osteotomy unit before and after reshaping. Part B modified from an original illustration by
Bill Winn.
or deformity of the shape of the affected bones and possible
compression of the underlying visceral structures (i.e., the
brain). Premature closure of the cranial vault sutures (cra­
niosynostosis) that do not extend into the cranial base will
have minimal effects on the maxillofacial form (e.g.,
metopic, unilateral coronal, and sagittal suture synostosis;
Figures 4-20, 4-21, and 4-22). However, prematurely fused
cranial vault sutures that extend into the cranial base will
also affect midfacial growth and development (e.g., Crouzon,
Apert, and Pfeiffer syndrome; Figures 4-23 through 4-26;
see Chapter 30).
C
Text continued on p. 102

D, Frontal views before and 1 year after
reconstruction. E, Facial views of patient at 5 years old. F and
G,
Computed
tomography
scan
views
before
and
after
reconstruction.
• Figure 4-20, cont’d 
D
©Elsevier Inc.
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SECTION 1  Basic Principles and Concepts
A
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• Figure 4-21  A child born with right unilateral coronal synostosis that resulted in
anterior plagiocephaly. He underwent anterior cranial vault and three-quarter orbital
osteotomies with reshaping when he was 9 months old. A, Facial and computed
tomography scan views before reconstruction. B, Illustrations of the craniofacial
skeleton in a child with unilateral coronal synostosis that resulted in anterior pla­
giocephaly before and after anterior cranial vault and three-quarter orbital osteoto­
mies. Part B modified from an original illustration by Bill Winn.
B1
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CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
C
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C, Bird’s-eye view of removed orbital osteotomy units before and after reshaping. D, Frontal views
before and 5 years after reconstruction. E, Oblique views 5 years after reconstruction.
• Figure 4-21, cont’d 
Continued

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SECTION 1  Basic Principles and Concepts
F
G
F and G, Computed tomography scan views of the cranial vault before and just after reconstruction.
• Figure 4-21, cont’d

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CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
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A
B
• Figure 4-22  A child born with sagittal synostosis that resulted in a scaphocephalic shape of the cranial vault that was characterized by
increased anteroposterior length and decreased bitemporal and biparietal width. It was not until the child was 2 years old that he was diagnosed
with sagittal synostosis. After a comprehensive evaluation, he underwent total cranial vault reshaping through a coronal (scalp) incision. He is
shown before and after a single-stage reconstruction. A, Frontal facial views before and after reconstruction. B, Profile facial views before and
after reconstruction.
Continued

98
SECTION 1  Basic Principles and Concepts
C, Illustrations of the craniofacial skeleton in a child with sagittal synostosis that resulted in scapho­
cephaly before and after total cranial vault and upper orbital osteotomies with reconstruction. Part C modified from an original
illustration by Bill Winn.
C1
C2
• Figure 4-22, cont’d

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CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
• Figure 4-23  A 6-month-old girl who was born with Apert syndrome and bilateral coronal synostosis. A, Facial and computed tomography
scan views without intervention. B, Profile and computed tomography scan views without intervention.
Orth
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Orth
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A
B

100
SECTION 1  Basic Principles and Concepts
• Figure 4-24  A 28-year-old woman with uncorrected Apert syndrome. She was unable to undergo craniofacial
or extremity reconstruction in her home country. Facial and extremity views are shown.
Orth
r ognathic Surg
r ery; J.C. Posnick
• Figure 4-25  A 50-year-old man who was born with Crouzon syn­
drome. His dysmorphic features include oxycephaly, orbital dystopia
with eye proptosis, and midface deficiency with an Angle Class III
malocclusion. Despite these difficulties, he is married and employed
as a taxicab driver; he also has a son with Crouzon syndrome.
©Elsevier Inc.
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CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
A
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• Figure 4-26  A 2-month-old child who was born with Pfeiffer syndrome (type I). She has bilateral coronal
synostosis that resulted in brachycephaly but without the suggestion of midface deficiency. A, Profile facial and
computed tomography (CT) scan views before intervention. B, Oblique facial and CT scan views before interven­
tion. C, Frontal facial and CT scan views before intervention.
Continued

102
SECTION 1  Basic Principles and Concepts
mandibular prognathism that resembles the human
variant.82,117,119 Harris and Johnson examined the longitu­
dinal records from the Bolton Brush Growth Study and
concluded that the heritability of maxillomandibular char­
acteristics is relatively high48 (Figures 4-28, 4-29, and 4-30).
It is assumed that approximately one third of children who
present with a severe Class III malocclusion will have a
parent with the same problem and that one sixth of these
children will have an affected sibling.73 Interestingly, a short
face growth pattern with a deep-bite malocclusion is found
more frequently in whites (see Chapter 23). Bimaxillary
dento-alveolar protrusion with anterior open-bite malocclu­
sion is more prevalent among blacks (see Chapter 24).112
The Class III skeletal pattern of maxillary deficiency
with relative mandibular excess is known to be more fre­
quent in certain races.2,73,84,123,139 Incidence rates of Class III
malocclusion of as high as 13% have been reported in spe­
cific regions of Asia.136 Lew and colleagues examined occlu­
sal parameters in 1050 Chinese school children between the
ages of 12 and 14 years. They found an incidence of 12.6%
for Class III malocclusion, 58.8% for Class I malocclusion,
and 21.5% for Class II malocclusion.67 Samman and col­
leagues investigated 300 Chinese individuals residing in
Hong Kong who were known to have a dentofacial defor­
mity and who had been referred to an “orthognathic surgery
clinic.” After excluding those individuals with cleft lip and
palate, 222 study patients remained. Forty-seven percent of
these individuals (n = 104) were found to have a Class III
skeletal growth pattern.106
Several of the common maxillomandibular disharmonies
are known to result from environmental influences (see
Chapters 10 and 21). The dental position in each arch and
the resulting occlusal variations are felt to have an even
greater environmental component.3,11,29,41,64,92 For example,
Overgrowth Syndromes and Anomalies
Acromegaly is caused by an anterior pituitary tumor that
secretes excessive growth hormone after the normal com­
pletion of growth.21 The response of specific growth centers
to abnormal serum levels of growth hormone is the overde­
velopment of the hands, the feet, the supraorbital ridges,
and the mandible. When there is excessive mandibular
growth, the position of the teeth within the bone and the
occlusion are also effected. An enlarged sella turcica (i.e.,
the resorption of bone in response to pituitary tumor
expansion) can be seen on a lateral cephalometric radio­
graph or a computed tomography scan (Fig. 4-27). Excess
growth hormone causes the proliferation of the condylar
cartilage of the mandible, thereby resulting in the bilateral
symmetric forward projection of the jaw. This overgrowth
continues until the serum growth hormone levels return to
normal. Unfortunately, the resultant skeletal deformities
persist. Other examples of maxillomandibular overgrowth
include hemifacial hypertrophy (see Chapter 31), hemi­
mandibular hyperplasia, and hemimandibular elongation
(see Chapter 22).
Hereditary Tendencies in the
Development of Dentofacial
Deformities
Jaw deformities are thought to be more common
among individuals with genetic backgrounds that are
crosses between different racial and ethnic groups as
compared with those from isolated human popula­
tions.10,32,40,57,59,60,62,83,85,86,91,93,108 It has been documented
that crossing different breeds of dogs and other mammals
can result in striking dentofacial deformities, particularly
D
D, Additional CT scan views before intervention.
• Figure 4-26, cont’d

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CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
• Figure 4-27  A middle-aged woman who presented for the orthodontic evaluation of a progressive malocclusion. She had a
normal occlusion, average facial features, and no distortions of the extremities earlier during life. Gradually, over the prior 5 years,
malocclusion and changes in facial and extremity morphology had occurred. At presentation to the orthodontist, standard records
were taken (lateral cephalometric and Panorex radiographs and dental models). The patient was then seen for surgical evaluation.
A review of the lateral cephalometric radiograph showed an enlarged sella turcica. An endocrinology consult confirmed the
diagnosis of acromegaly. Appropriate treatment was undertaken without further worsening of the facial or extremity deformities.
A, Facial and occlusal views at presentation indicate growth hormone changes. B, Profile and lateral cephalometric views at
presentation. Note the enlarged sella turcica. C, A view of the dorsal aspects of hands indicates growth hormone changes.
A
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• Figure 4-28  Biologic identical twin sisters are shown during their teenage years to confirm a hereditary tendency toward the
occurrence of developmental jaw deformities with malocclusion. A, Facial and occlusal views of Twin A demonstrating bimaxillary
dental protrusion with jaw disharmony and anterior open-bite malocclusion. B, Facial and occlusal views of Twin B demonstrating
bimaxillary dental protrusion with jaw disharmony and anterior open-bite malocclusion.
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• Figure 4-29  A father and his biologic daughters are shown during the daughters’ teenage years to confirm a hereditary ten­
dency toward the occurrence of developmental jaw deformities with malocclusion. A, Facial and occlusal views of the father that
demonstrate a Class III skeletal pattern.
Continued
dento-alveolar morphology is commonly affected by thumb
sucking and other para-oral habits (i.e., environmental
influences; Figures 4-31 and 4-32). The more severe the
dentofacial deformity, the more likely that inheritance plays
at least a partial role. Maxillary deficiency with relative
mandibular excess (i.e., a Class III skeletal pattern) and
maxillomandibular deficiency (i.e., the short face growth
pattern) are both thought to have a significant hereditary
component.31,36,58,79,116,120,137
Environmental and Neuromotor Effects
on Skeletal Growth
The mandible can be viewed as a somewhat malleable block
of hard tissue that is adjacent to the skull base. It is separated
from the skull by working temporomandibular joints. It
houses the inferior alveolar neurovascular bundle, and it
provides a matrix for the formation, eruption, and eventual
alignment of the teeth. Muscular activity in the head and
neck can directly affect skeletal growth through one of the
following mechanisms: 1) hyperactivity of muscles at the
point of attachment may cause excessive skeletal remodeling
or contour deformities (as discussed later in this chapter)
2) hypoactivity of the masticatory muscles may cause distor­
tions of the normal skeletal growth (i.e., long face growth
pattern; Fig. 4-33) and 3) hyperactivity of specific muscles
such as the sternocleidomastoid (i.e., torticollis) may result
in the deformation of the growing bones (i.e., cranial vault,
orbit, and zygoma; Fig. 4-34).71
Muscle and Soft-Tissue Effects on
Skeletal Growth
Experimental animal research and clinical observational
studies confirm that the influences of the mandibular rest
posture, the neck rest posture, and the tongue and lip rest posi­
tion of the affected individual’s eventual facial morphology
are real and more important than the effects of intermittent
muscle contracture (see Chapters 8 and 10).128-130 It is also
known that functional stresses that are placed on the skel­
eton will increase bone density.113,114,118 A corollary is that,
during periods of inactivity (e.g., mandibular and neck rest
posture), skeletal demineralization occurs.
Erupting teeth carry alveolar bone with them. Therefore,
forces that counteract the normal eruption of teeth can
shape the dental arches and the alveolar processes of both
the maxilla and the mandible.5,101-105,107,109,111,126,140 Experi­
mental studies confirm that pressure against the active erup­
tion of the teeth that is maintained for 4 to 6 hours can
affect tooth movement and initiate bone remodeling (see
Chapter 5). Habits such as finger or thumb sucking, which
apply consistent pressure against the teeth, can have the
Text continued on p. 113

106
SECTION 1  Basic Principles and Concepts
C
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B, Daughter A with a similar class III skeletal pattern. C, Daughter B with a similar Class III skeletal pattern.
• Figure 4-29, cont’d 
B
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107
CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
A
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• Figure 4-30  Biologic twin sisters are shown during their teenage years to confirm a hereditary tendency toward the occurrence
of developmental jaw deformities with malocclusion. A, Facial and occlusal views of Twin A demonstrating a long face Class III
growth pattern. B, Facial and occlusal views of Twin B demonstrating a similar long face Class III growth pattern.
B
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• Figure 4-32  A 12-year-old girl was referred by an orthodontist for surgical evaluation. She had persistently sucked her
thumb since infancy. This parafunctional habit resulted in the severe deformity of her maxilla and mandible. The upper jaw
has a constricted arch width and an excessive curve of Spee, whereas the mandible has a Class III reversed curve of Spee.
A severe anterior open-bite malocclusion is also present.
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• Figure 4-31  A 10-year-old girl with a severe anterior open bite. She demonstrates how a para-oral
habit (thumb sucking) can exert the long duration of light force at the periodontal ligament that is
required to move the teeth. This patient was a consistent and constant “thumb sucker” from soon
after her birth and throughout the mixed dentition.
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109
CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
Orth
r ognathic Surg
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A
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• Figure 4-33  A teenage girl with a lifelong history of obstructed nasal breathing demonstrates the resulting long face growth pattern. The nasal
obstruction resulted in forced mouth breathing with an open-mouth posture. This in turn is associated with maxillary dental hypereruption (i.e.,
hypereruption of the molars greater than the incisors), a steep mandibular plane, anterior open-bite Class II malocclusion, and increased lower
anterior facial height. Clinically, there is a “gummy” smile, lip incompetence, and a flat, long face. A, Frontal views with smile before and after
reconstruction. B, Profile views before and after reconstruction.
Continued

110
SECTION 1  Basic Principles and Concepts
Prior to retreatment
After treatment
Pre surgery
C
C, Occlusal views before retreatment, with orthodontic decompensation in progress, and after the completion
of treatment.
• Figure 4-33, cont’d

111
CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
D
Maxillary counter-
clockwise rotation
Mandibular counter-
clockwise rotation
Arch expansion
E
• Figure 4-33, cont’d  D, Articulated dental casts that indicate analytic model planning. E, Cephalometric radiographs before and after surgery.

A
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• Figure 4-34  A child with right-sided congenital muscular torticollis and C1-C2 rotary subluxation. Ipsilateral right fronto-orbital flat­
tening and contralateral left occipitoparietal flattening were noted. The right sternocleidomastoid muscle (SCM) remained tight when the
patient was 2 years old. He underwent surgical release of the SCM, and this was followed by neck range-of-motion exercises with
good maintenance of function. A degree of right fronto-orbital flattening (skull molding) remains. A, Frontal view with the neck in a relaxed
position before treatment indicated a head tilt. Computed tomography scan views indicate fronto-orbitozygomatic asymmetry as a result
of skull molding. B, Intraoperative view of the tight SCM and the proposed incision site, and a close-up view of the exposed SCM
before release. C, Frontal views before and 2 years after neck muscle release. Residual fronto-orbital (skull molding) flattening remains.
From Slate RK, Posnick JC, Armstrong DC, et al: Cervical spine subluxation associated with congenital muscular torticollis and cranio­
facial asymmetry. Plast Reconstr Surg 91:1187–1195, 1993.
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113
CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
same effect on the shaping of the dental arches (see Figs.
4-31 and 4-32). It seems as though the intensity (i.e., the
amount of force) against the teeth is less important than the
duration (i.e., the number of hours per day) with regard to
causing this effect.
It has been confirmed that the postural position of the
tongue at rest (e.g., the mandible open with the constant
protrusion of the tongue) rather than where the tongue is
placed during function (e.g., a tongue-thrust swallowing
habit) is most important for determining the eventual posi­
tion of the teeth and the morphology of the dento-alveolar
complex.61,121 The intermittent forces that are generated
against the teeth during chewing, swallowing, and speaking
are documented to be more than heavy enough to produce
tooth movement. However, during these normal functions,
the force is not maintained long enough at any point in time
to have an appreciable effect on the position of the teeth or
the morphology of the bone.35 Even repetitive intermittent
“abnormal” tongue and lip contraction with resulting pres­
sure on the teeth during swallowing and speaking (i.e.,
tongue thrusting)—despite their frequency—do not sum up
to the number of hours of force required to produce a patho­
logic effect. By contrast, even very light forces sustained for
a long duration (i.e., the tonic con­tracture of masticatory
muscles to maintain mandibular posture) can affect both the
path of tooth eruption and jaw development.8,94
It is known that muscles of different size and force that
attach to the mandible at specific locations will result in
characteristic ridges and contours (e.g., gonial angles, coro­
noid process, genial tubercle).12,13 For patients with the
condition known as masseteric muscle hypertrophy, there is
excess bone proliferation at the masseter muscle’s point
of attachment along the inferior border of the mandible (i.e.,
the gonial angle ridge) in response to greater than average
muscle forces.43 By contrast, in patients with muscular dys­
trophies (i.e., hypotonic cerebral palsy, Moebius syndrome
with cranial nerve palsy), the ramus may be short, and the
gonial angles appear to be underdeveloped as a result of the
limited muscle forces applied to these same regions.100
The lips, cheeks, and tongue contain muscles in their
deep layers that exert varied pressures against the teeth and
the alveolar process. They normally do so with a constant
level of tone while at rest as well as during dynamic func­
tion. These light (tone) forces applied for a long duration
are known to cause tooth movement and remodeling of the
alveolar process. It is the “resting” postural pressures of these
structures (i.e., lips, cheeks, tongue, and muscles), the pres­
ence of para-oral habits (i.e., thumb sucking, pencil biting;
see Figs. 4-31 and 4-32), and the man-made and controlled
orthodontic pressure that can exert the long duration of
light force at the periodontal ligament that is required to
move teeth.55 When the difference between applied ortho­
dontic forces and pressures of the tongue, cheek, and lips
that counteract those forces applied to the periodontal liga­
ment becomes great enough for sustained periods of time,
tooth movement will occur. Another example of dental
adaptation is seen when the constant strong force of the
tongue is juxtaposed with intrinsic weaker bilabial (i.e.,
upper and lower lip) muscle tone forces.135 This results in
the predictable dental compensations (i.e., proclined maxil­
lary and mandibular incisors) observed in patients with
bimaxillary dento-alveolar protrusion (see Chapter 24). This
also explains the consistent dental compensations that are
typically observed in patients with specific developmental
dentofacial deformities such as long face growth pattern (see
Chapter 21 and Fig. 4-33) or isolated mandibular defi­
ciency (see Chapter 19).122
Severe scar contracture of the anterior neck and lower lip
soft tissues from a burn that occurred during childhood will
also affect mandibular morphology. The soft-tissue contrac­
ture will distort ongoing skeletal growth and cause the
mandible to be retrusive, with an obtuse angle. The chin
region of the mandible will grow with increased vertical
length and without sagittal prominence, and there will be
an anterior open-bite malocclusion. This deformity and its
surgical correction were first described by Simon Hullihen
in 1849 (see Chapter 2 and Fig. 2-19).
When an electric burn to an oral commissure occurs during
childhood and results in soft-tissue contracture with micro­
somia, the constant soft-tissue forces against the teeth will
distort the shape of the dental arch and the alveolar process.
There will be anterior dental crowding, tipping of the inci­
sors, and malocclusion.
With the congenital absence of part or most of the tongue,
there will be a characteristic V-shaped deficiency or dysmor­
phology of the mandibular dental arch (e.g., hypoglossia–
hypodactylia syndrome; Fig. 4-35).15 In the presence of a
volumetrically enlarged tongue (e.g., vascular malforma­
tion, hemangioma, neurofibromatosis, Proteus syndrome,
Beckwith-Wiedemann syndrome), there will be dento-
alveolar effects that result in spaces between the teeth (Fig.
4-36). The lower anterior teeth will be flared, and the overall
mandibular arch form will be enlarged. The important
factor that causes these dental compensations and arch form
deformities is the sustained and constant rest forces of the
oversized tongue on the teeth and bone and not what the
tongue does when it is in motion.
In the individual with a normal tongue volume and
neuromotor capability, it is known that the rest position of
the tongue in the mouth is primarily influenced by respira­
tory factors.73 It is the rest position of the tongue that influ­
ences the pattern of dentofacial development rather than
the position of the tongue during function.
In the presence of chronic nasal obstruction, a typical long
face growth pattern with anterior open-bite malocclusion is
likely to occur. In these circumstances, a speech therapist
may have success with teaching the individual altered move­
ment of the tongue for the formation of more accurate
voluntary independent speech sounds.90 However, unless
the anterior open bite and the nasal obstruction are cor­
rected, the myofunctional therapy will not allow the indi­
vidual to reliably position his or her tongue, lips, teeth, and
mandible for correct articulation during rapid conversa­
tional speech (see Chapter 8).

114
SECTION 1  Basic Principles and Concepts
• Figure 4-35  A 10-year-old girl who was eventually diagnosed with hypoglossia–hypodactylia syndrome. In this photo, she dem­
onstrates how the congenital absence of part or most of the tongue will result in a characteristic V-shaped deficiency and dysmor­
phology of the mandibular dental arch and how this will negatively affect the maxillary arch form.
Palatal view
Facial-occlusal view
Lingual view
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©Elsevier Inc.
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• Figure 4-36  A 3-year-old child with a congenitally enlarged tongue is shown. The secondary
effects on the oral cavity include a Class III anterior open-bite malocclusion and a lateral cross-
bite malocclusion.
In the skeletal Class III adult patient (i.e., a retrusive
maxilla with relative mandibular excess) who undergoes
successful orthognathic correction, a normal oral cavity
volume and a normal occlusion are established. Interest­
ingly, in most cases, the tongue position and lip posture will
then naturally adapt to the new morphology.80,81
Clinical observation confirms that, when an individual
with a longstanding dentofacial deformity undergoes suc­
cessful reconstruction, it is generally not necessary to retrain
the tongue with active myofunctional therapy. This only
needs to occur under the following conditions: 1) when
the tongue volume is truly excessive (e.g., vascular

115
CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
malformation, neurofibromatosis) 2) when there is the pres­
ence of intrinsic neuromotor dysfunction (e.g., cerebral
palsy) or 3) when the nasal airway remains obstructed and
a failure of tongue adaptation is seen.63
Respiration Patterns and Their Effects on
Skeletal Growth
Harvold conducted primate experiments that were designed
to test hypotheses regarding the relationship between nasal
obstruction, mouth breathing, mandibular rest posture, tongue
rest position, jaw growth, and dental malocclusion.49-54 He
created an experimental model in growing rhesus monkeys
(Macaca mulatta) to study these relationships. To do this, he
completely obstructed the nasal passages in the study sub­
jects with silicone nose plugs. The experiments showed that
the monkeys adapt to total nasal obstruction in two different
ways. Predominantly, the experimental animals maintained
an open-mouth posture with tongue protrusion. Interest­
ingly, some adapted to a forced oral airway by holding the
upper and lower teeth close together but with wide lip sepa­
ration. Nevertheless, both adaptive mandibular, tongue, and
lip positioning patterns gradually resulted in maxilloman­
dibular dysmorphology and dental malocclusion that was
notably different from that seen in the control animals.
In the experimental animals, morphologic changes that
occurred in the lips, tongue, dentition, jaws, and mandibu­
lar posture were documented by the research team through
cephalometric measurements as well as through electromyo­
graphic and behavioral findings. Harvold’s cephalometric
findings documented changes in facial height (e.g., of the
naso-palatal plane and the symphysis-palatal plane) and
alterations in mandibular morphology.
As stated, a minority of animals adapted to the nasal
airway blockage by holding their teeth together with wide
lip separation (rather than maintaining an open-mouth
posture with tongue protrusion) while still breathing
through their mouths. This subgroup showed the least
change in jaw morphology and dental alignment.
The observed morphologic and occlusal changes were
most extreme when the mandible constantly remained
open, with tongue protrusion (i.e., an open-mouth posture).
The adaptive lowering of the mandible (with clockwise rota­
tion) to achieve effective oral respiration was followed by
secondary changes in the maxilla, including a downward
displacement (i.e., vertical lengthening) of the alveolar
process in conjunction with excess extrusion of the teeth.
When molar (posterior) hypereruption was significantly
greater than incisor hypereruption, an anterior open-bite
malocclusion developed (Fig. 4-37).127
It became apparent to Harvold that the changes in man­
dibular shape and the direction of mandibular growth (i.e.,
clockwise rotation) observed in a majority of the experimen­
tal monkeys were dependent on the adaptive activity of the
facial, tongue, jaw, and neck muscles in response to respira­
tory need. Interestingly, in Harvold’s experimental animal
model, there was no indication of abnormal bony
apposition on the condyles in association with the forced
oral respiratory pattern. The apposition of new bone on the
condyles continued (in the usual way) independently of
aberrant mandibular positioning or open-mouth posture.107
In review, the growing experimental animals studied by
Harvold coped with nasal obstruction by changing neck,
tongue, facial, and masticatory muscle tone, thereby result­
ing in alterations in mandibular posture and tongue posi­
tion.44,45,55 The animals typically did this in one of two
different ways but always with the goal of maintaining
adequate respiration. This resulted in varied but consistent
secondary changes in the maxillomandibular morphology
(i.e., developmental jaw deformity) and dental compensa­
tions (i.e., malocclusion). The measured lower facial height
increase that occurred in the presence of a constant open-
mouth posture was primarily the result of maxillary molar—
and, to a lesser extent, incisor dental—hypereruption (e.g.,
long face growth pattern).
Harvold also reviewed the human observation studies of
Linder-Aronson and colleagues and found that they paral­
leled his experimental animal research.68-70,75-78 Their clinical
research established that nasal obstruction with forced mouth
breathing (i.e., open-mouth posture) in humans is fre­
quently associated with maxillary dental extrusion, a steeper
than normal mandibular plane, anterior open-bite maloc­
clusion (i.e., the hypereruption of the molars is greater than
that of the incisors), and increased lower anterior facial
height. Similar to Harvold’s experimental monkeys, growing
humans may develop different neuromotor adaptations
to cope with nasal obstruction and the need to maintain
adequate respiration. The secondary skeletal and dental
morphologic deviations will therefore vary, but they tend
to occur in a predictable long face growth pattern (see
Chapter 21).39,125,133,134
Humans with severe hypoplasia of the maxilla, a retropo­
sitioned palate and a restricted nasal airway, as are seen in
patients with Crouzon or Apert syndrome, also become
dependent on oral respiration (see Chapter 30).4 With
Crouzon or Apert syndrome, the individual’s neck is often
maintained in hyperextension with an open-mouth posture,
the protrusion of the tongue, and the clockwise rotation of
the mandible; this head and neck posture is compensatory
to support respiration. During the day, this compensatory
posture may be sufficient, but it becomes inadequate at night
and results in obstructive sleep apnea (see Chapter 26).4
When these compensatory adaptive changes occur during
childhood, they contribute to additional secondary maxil­
lomandibular skeletal dysmorphology with growth that
further affects the occlusion (see Chapter 30).7,33,115 This is
an example of a congenital midface deformity that is further
influenced by the environment.
Congenital Myopathies and Effects on
Skeletal Growth
Individuals
with
congenital
myopathies
constitute
a heterogeneous subgroup of patients with congenital

116
SECTION 1  Basic Principles and Concepts
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r ery; J.C. Posnick
C
• Figure 4-37  A 16-year-old with a nonprogressive congenital myopathy that resulted in a constant open-mouth posture. He developed a long
face growth pattern that was characterized by severe maxillary vertical excess and protrusion, a retrusive mandible, and an Angle Class II maloc­
clusion. He underwent a combined orthodontic and surgical approach. Orthodontic manipulation was limited as a result of hygiene control. The
surgery included a maxillary Le Fort I osteotomy (vertical intrusion, first bicuspid extractions, and alveolar bone removal with premaxillary setback
and cant correction) and sagittal split osteotomies of the mandible (clockwise rotation and asymmetric correction). A, Frontal views with smile
before and after reconstruction. B, Oblique facial views before and after reconstruction. C, Occlusal views before and after reconstruction.

117
CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
D
E
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D and E, Articulated dental casts that indicates analytic model planning.
F, Lateral cephalometric radiographs before and after reconstruction.
• Figure 4-37, cont’d

118
SECTION 1  Basic Principles and Concepts
neuromuscular disorders in which the pathology is attribut­
able to defects in the muscle fibers rather than in the
neurons. Congenital fiber-type disproportions are rare con­
genital myopathies that are considered slow or nonprogres­
sive. Patients with these conditions, like those with other
types of primary myopathies, will generally exhibit facial
features that often result in what is described as a “myo­
pathic face.” The “myopathic face” has many similarities to
the “adenoid face” that is seen in children with a blocked
nasal airway due to enlarged adenoids and other intranasal
obstructions, which result in an open-mouth posture. These
abnormal human maxillomandibular growth patterns are
also consistent with the findings reported by Harvold when
rhesus monkeys were forced to maintain an open-mouth
posture during jaw growth, as described previously in this
chapter. The “myopathic face” findings described by
Lehman and colleagues include characteristics of an
increased lower anterior facial height, incompetent lips, a
high-arched palate, and often anterior open-bite malocclu­
sion (Figs. 4-37 and 4-38).66 Clinical human and animal
model studies confirm that these features are to be expected
in the presence of an open-mouth posture during jaw
growth, no matter what the cause. Although blocked nasal
breathing is the most common cause of an open-mouth
posture during growth, clearly congenital myopathies that
also result in an open-mouth posture will produce the same
facial dysmorphology.
Effects of Trauma on Skeletal Growth
Intrauterine compressive force against the developing face is
a form of trauma that can lead to deformations of the cra­
niofacial skeleton that are visually present at the time of
birth. For example, when there is a decrease in the volume
of amniotic fluid, the fetus’ head is typically flexed tightly
against his or her chest in utero. The compressive forces to
the chin will prevent the mandible from achieving its full
prenatal growth potential. The normally developing tongue
is then forced to rest high in the mouth, thereby preventing
approximation and fusion of the lateral maxillary processes.
At the time of birth, clefting of the secondary palate is
recognized. A pathologic process continues after birth, and
this includes retrognathia, a cleft of the secondary palate,
and varying degrees of respiratory distress as a result of the
otherwise normal tongue resting superior and posterior in
the mouth. This intrauterine deformation is responsible for
approximately two thirds of those individuals with observed
Robin sequence at the time of birth. Significant but incom­
plete catch-up mandibular growth is expected. In general,
there will be sufficient mandibular growth in combination
with an expected degree of maxillary growth inhibition
from cleft palate repair during childhood that results in
maxillomandibular harmony but at least mild horizontal
deficiency and the clockwise rotation of both jaws. Indi­
viduals with these features are typically managed with
orthodontics to achieve an acceptable occlusion, but this
does result in a degree of facial dysmorphology (see Fig.
4-20). Unless upper airway obstruction with obstructive
sleep apnea is confirmed, the degree of maxillomandibular
deficiency is such that a surgical consult is generally not
requested.
An infant, child, or young adolescent who sustains injury
to the craniofacial skeleton has the potential for growth dis­
turbance of the injured bones. This is in addition to any
skeletal deformity that remains if the fracture was not fully
reduced with satisfactory initial healing (see Chapter 35).
During some difficult deliveries through the vaginal canal,
especially those that require forceps, damage to one or both
of the temporomandibular joints or fracture of the man­
dible can occur. In modern times, with good prenatal care
and skilled obstetrics support being available at the time
of delivery, birth trauma to the mandible has become a
rare event.
A childhood injury to the cartilage of the nasal septum
may result in nasal deformity. It may also lead to deficient
midface growth (see Fig. 35-2).38 This has been confirmed
in experimental animals and documented through clinical
observation in humans.28 In experimental animals, when
the cartilage of the nasal septum is removed before growth
is complete, there will be a dramatic decrease in the hori­
zontal and vertical growth of the midface. Whether this is
the result of a mechanical collapse with a secondary loss of
growth velocity of the maxilla or an intrinsic growth restric­
tion of the upper jaw remains open to question.
Trauma to the growing mandible that is severe enough to
cause fracture and the displacement of the fragments is also
known to result in secondary progressive growth deformi­
ties, at least in some cases. There are thought to be three
major sites of mandibular growth that may be affected:
1. The mandibular condyle: Proliferating cartilage at the
base of the fibrocartilage layer that covers the articular
surface results in mandibular growth. At the completion
of mandibular growth, the fibrocartilage layer is replaced
by bone.
2. The outer surfaces of the ramus: Extensive remodeling
of the mandible through the apposition of bone on the
posterior and outer surfaces along with resorption on the
anterior and inner surfaces is known to occur and is
influenced by muscle forces and the compression of the
associated soft tissues (e.g., tongue volume) within the
mouth.
3. The alveolar process: New alveolar bone is added only as
individual teeth develop and erupt into the arch.
In individuals who sustain a displaced condylar neck frac­
ture, a sequence of events generally occurs that includes the
contraction of the lateral pterygoid muscle with the dis­
placement of the condylar fragment anteriorly and medially
(Fig. 4-39). The displaced fragment (i.e., the medial pole of
the condyle or the total condyle) has a tendency toward a
degree of resorption and malunion. This may then result in
a loss of posterior facial height, with a shift of the ipsilateral
Text continued on p. 124

119
CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
©Elsevier Inc.
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• Figure 4-38  A 17-year-old boy who was born with a
nonprogressive congenital myopathy was referred by an
orthodontist for surgical evaluation. The lack of mastica­
tory muscle strength resulted in a constant open-mouth
posture. The long face growth pattern is characterized
by vertical maxillary excess, a clockwise rotated retrusive
mandible, a vertically long and retrusive chin, and an
anterior open-bite malocclusion. The patient underwent
a combined orthodontic and surgical approach. Four
bicuspid extractions relieved dental crowding. This
was followed by surgery that included a maxillary Le Fort
I osteotomy (vertical intrusion and horizontal advance­
ment); bilateral sagittal split osteotomies of the mandible
(horizontal advancement); and osseous genioplasty (ver­
tical reduction and horizontal advancement). A, Frontal
views in repose before and after reconstruction.
B, Frontal views with smile before and after reconstruc­
tion. C, Profile views before and after reconstruction.
Continued

120
SECTION 1  Basic Principles and Concepts
Prior to treatment
After treatment including 4 bicuspid extractions
D
E
F
D, Occlusal views before and after reconstruction. E, Articulated dental casts that indicate analytic
model planning. F, Lateral cephalometric radiographs before and after surgery.
• Figure 4-38, cont’d

121
CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
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Displaced condyle fracture
A
• Figure 4-39  A 5-year-old girl sustained a right condyle fracture of the mandible and then presented as a teenager
with resulting facial asymmetry involving the maxilla and the mandible. She had full painless mandibular mobility.
She then underwent a combined orthodontic and orthognathic approach that included a Le Fort I osteotomy (cant
correction), bilateral sagittal split ramus osteotomies (asymmetry correction), an osseous genioplasty (horizontal
advancement), and intranasal procedures (septoplasty, inferior turbinate reduction, and nasal recontouring) during
her teenage years (see Chapter 35). A, Frontal view when the patient was 6 years old, which was 1 year after the
right condyle fracture. The anteroposterior facial radiograph indicates a medially displaced right condyle fracture.
B, Frontal view when the patient was 15 years old. An anteroposterior cephalometric radiograph confirms the result­
ing facial asymmetry that primarily involved the mandible but that now also involves the secondary deformity of the
maxilla and the chin.
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B
Continued

122
SECTION 1  Basic Principles and Concepts
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C, Articulated dental casts that indicate analytic model planning. D, Frontal views before and after
reconstruction.
• Figure 4-39, cont’d 
C
Roll Orientation Correction

123
CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
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E, Profile views before and after reconstruction. F, Occlusal views before and after
reconstruction. G, Posteroanterior cephalometric radiographs before and after reconstruction.
• Figure 4-39, cont’d

124
SECTION 1  Basic Principles and Concepts
posterior facial height, ipsilateral mandibular hypoplasia,
and secondary deformity of the contralateral side of the
mandible, the maxilla, and the chin region. This sequence
of events results in significant maxillomandibular asymme­
try and disproportion (see Fig. 35-8). There are also numer­
ous reported examples of bony ankylosis of the condylar
stump to the glenoid fossa after the fracture of the condyle
(see Fig. 35-1).
Effects of Tumors and Growths on
Skeletal Growth
The presence of a sustained expansile mass (e.g., cyst, cellular
tumor, skeletal mass) will distort the normal growth and
morphology of the bones that are being compressed or exp
anded.1,6,9,20,24,26,34,46,87-89,95-99 Frequent examples of this
occurrence in the maxillofacial region include the effects of
neurofibromatosis, vascular malformations, Proteus syn­
drome, fibrous dysplasia, and odontogenic tumors and cysts
(Fig. 4-40). In the adult, the compressive forces of a tumor
mass may cause resorption and even result in pathologic
fracture. The tumor mass may also compress visceral struc­
tures and cavities, thereby causing an impairment of func­
tion. Depending on the tumor’s location, volume, and
velocity of expansion, there may be alterations in cognitive
function, vision, speech, breathing, swallowing, chewing,
lip control, hearing, neck range of motion, or mandibular
range of motion. When radiation therapy is required for the
management of a malignancy, damage to the adjacent soft
tissues and skeletal structures frequently occurs. The arrest
of growth in irradiated immature bones may result in orbital
dysplasia, zygomatic hypoplasia jaw deformity with maloc­
clusion, and damage to the developing teeth and periodon­
tium (Fig. 4-41).
Conclusions
The term dentofacial deformity is generally used to describe
a significant disproportion of the jaws that is associated with
malocclusion. Knowing the etiologic factors of a jaw defor­
mity can be important to the fundamental understanding
of how and when to treat the problem. According to current
knowledge, factors that are known to cause or result in
dentofacial deformities can be subdivided to include known
syndromes and anomalies, hereditary tendencies, environ­
mental and neuromotor effects, effects of trauma, and
effects of tumors and growths.
mandible toward the affected side. In these cases, an asym­
metric retrusive lower jaw and predictable malocclusion can
be documented when the jaw is placed in centric relation.
Experimental and clinical studies confirm that the ability of
the individual’s mandible and masticatory muscles to adapt
will determine the degree of eventual jaw deformity and
residual malocclusion as well as what treatment is needed
(see Chapter 35).
When significant condylar trauma occurs during child­
hood, with or without fracture, there will have been injury
to the fibrocartilage, with a potential effect on growth. If in
fact the “condylar cartilage–push theory” of mandibular
growth is all important, a devastating growth distortion
should occur over time in all affected individuals. Walker
tested this theory by deliberately producing condylar frac­
tures in young monkeys and then observing the effect of
these fracture on subsequent growth.131,132 He was unable
to document a consistent progressive mandibular deficiency
or deformity with malocclusion. Mandibular growth that
approximated normal occurred in the majority of experi­
mental animals. Late postmortem gross and histologic
evaluation confirmed that there was regeneration of the
condylar process with a new layer of cartilage over the
articular surface that was identical to the contralateral (non­
injured) side. Clinical studies on a series of human children
who sustained similar condylar neck fractures confirmed the
potential to regenerate bone that approximated the lost
(injured) condyle adverse effects on growth in many of the
cases.42,74 It also became evident from these studies that a
notable minority (approximately 25%) of affected individu­
als do sustain significant growth disturbances (i.e., man­
dibular hypoplasia or asymmetry) after a condylar injury,
often with secondary deformity in the growing maxilla (see
Fig. 4-39). The explanation for this variation in human
response (i.e., repair versus deformity) is likely dependent
on the following: 1) the extent of initial injury; 2) the extent
of resulting scarring or the lack of regenerative potential; 3)
the variable importance of the condyle as a growth center
in each individual child; and 4) the variable adaptive ability
of the muscles of mastication (see Chapter 35).
Over the decades, clinicians have confirmed the work of
Gilhuus-Moe 42 and Lund74 by documenting a spectrum of
possible outcomes after condylar fracture. Reports confirm
instances in which the fracture dislocation of a condylar
process has occurred and is followed by a continued normal
downward and forward translation of the mandibular
body with regeneration of a neocondyle back to baseline.
Other clinical reports show a complete loss of the condylar
morphology without regeneration followed by decreased

125
CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
©Elsevier Inc.
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C.
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©Elsevier Inc.
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Surg
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C.
C.
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©Elsevier Inc.
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©Elsevier Inc.
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©Elsevier Inc.
Or
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O thththththththththththththththththththththththththtr ogn
gn
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g atatatatatatatatatatatatatatatatatatatatata hicicicicicicicicicicicicicicicicic Su
Su
Su
Su
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Su
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Su
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Su
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ry
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ry
ry
ry
ry
ry
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C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C. Pos
os
os
os
os
os
os
os
os
os
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o nicicicicicicicicicicicicicicicicicicicicicicicicicick
A
• Figure 4-40  A 5-year-old girl with poly­
ostotic fibrous dysplasia with massive
involvement of the maxilla and mandible
bilaterally. An asymmetric swelling of the
mandible (left greater than right) was
first recognized when the child was 18
months old; it rapidly enlarged, and maxil­
lary involvement became evident with
the deterioration of breathing, chewing,
speech, and swallowing. Pathologic frac­
tures were sustained in all four extremities
as a result of the involvement of fibrous
dysplasia. A, Frontal and computed
tomography scan views before surgery.
B, Oblique facial views before and after
reconstruction. C, Profile facial views
before and after reconstruction.
Continued

126
SECTION 1  Basic Principles and Concepts
D
E
D and E, Computed tomography views before and after a debulking procedure. From
Posnick JC, Hughes CA, Milmoe G, et al: Polyostotic fibrous dysplasia: an unusual presentation in childhood. J Oral
Maxillofac Surg 54:1458–1464, 1996.
• Figure 4-40, cont’d

127
CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
O ththththththththththththththth
r ogn
gn
gn
gn
gn
g atatatathicici Su
Su
Su
Surg
r ery
ry; J.C.
C.
C.
C Pos
os
os
os
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A
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Orthththththththththththththththth
r ogn
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gn
gn
gnatatatatatatatatata hicicicicicic Su
Su
Su
Surg
r ery
ry
ry
ry
ry
ry
ry
ry
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ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
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os
os
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os
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os
os
os
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o nicicicicicicicicicicicicicicicicicicicicicicicicick
B
• Figure 4-41  A teenage girl who at 9 years of age was found to have a malignancy of the parameningeal region. Biopsy confirmed the
diagnosis of rhabdomyosarcoma. She was treated with surgical debulking, chemotherapy, and radiation according to intergroup protocols.
There was resulting radiation growth disturbance of the skeletal and soft-tissue structures. The patient underwent staged reconstruction,
including stage I serratus muscle microvascular transfer to the left temporal region in combination with full-thickness autogenous cranial
graft reconstruction of the left zygomatic orbital complex when she was 13 years old. This was followed when she was 16 years old by
further staged orthognathic reconstruction to manage the jaw deformity and the malocclusion. The orthodontic portion of her treatment was
carried out cautiously, because there was radiation injury to her left posterior maxillary and mandibular dentition. The procedures included
maxillary Le Fort I osteotomy in two segments with interpositional autogenous iliac (hip) grafting, bilateral sagittal split ramus osteotomies
of the mandible, and an osseous genioplasty. Septoplasty, inferior turbinate reduction, and recontouring of the floor of the nose were also
carried out to open the airway. A, Facial and occlusal views are shown when the patient was 12 years old, before reconstruction. B, Oblique
facial and computed tomography scan views when the patient was 12 years old, before reconstruction.
Continued

128
SECTION 1  Basic Principles and Concepts
Or
Or
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O thththth
r ogn
gn
gn
gn
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gnatatatatata hicicicicicicicicicicicici Su
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ry
ry
ry
ry
ry
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ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
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os
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os
os
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os
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C
Orbito-zygoma hypoplasia
Maxillary
hypoplasia
Mandibular
hypoplasia
Or
Or
Or
Or
Or
Orththththththththththththththththththth
r ogn
gn
gn
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C.
C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
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Or
Or
Or
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Orththththththththththththththththththththththththththththtr ogn
gn
gn
gn
gn
gn
g atatatatatatatatatatatatatata hicicicicicicicicicicicicicicicicicici Su
Su
Su
Su
S rg
r ery
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C. Pos
os
os
os
os
os
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os
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o nicicicicicicicicicicicicicicicicicicicicicick
D
Or
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Orththththththththththththththththththththth
r ogn
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gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
g atatatatatatatatatatatatatatatatatatathicicicicicicicicicicicicicicicicicici Su
Su
Su
Su
Su
Su
S rg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
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os
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os
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os
os
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E
C, Profile facial and computed tomography scan views when the patient was 12 years old, before
reconstruction. D, Before and 1 year after left zygomatic and orbital cranial graft reconstruction and serratus muscle
free-tissue transfer reconstruction. E, Frontal and occlusal views when the patient was 13 years old, with orthodontics
in progress in preparation for jaw reconstruction.
• Figure 4-41, cont’d

129
CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
F
Maxillary counter-
clockwise rotation
Mandibular counter-
clockwise rotation
Arch expansion
Roll Orientation Correction
G
H
Or
Or
Or
Or
Or
O thththththththth
r ogn
gn
gn
g athicic Su
Su
Surg
r ery
ry; J.C.
C.
C Pos
os
os
os
os
o nicicici k
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Orththththththththththththththththththththtr ogn
gn
gn
gn
gn
g atatathicicicic Su
Su
Su
Surg
r ery
ry
ry
ry; J.C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
osnicicicicicicicicicicicicicicicicicick
F, Panorex radiograph when the patient was 13 years old, with preoperative orthodontics complete
in preparation for jaw reconstruction. Note the short dental roots on the left side. G, Articulated dental casts that indicate
analytic model planning. H, Frontal facial views in repose before and after reconstruction.
• Figure 4-41, cont’d 
Continued

130
SECTION 1  Basic Principles and Concepts
I
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
O thththththththththththththththththththth
r ogn
gn
gn
gn
gn
g atatatatatatathicici Su
Su
Surg
r ery
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
o nicicicicicicicicicicicicicicick
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Orthththththththththththththththththththththththththththththth
r ogn
gn
gnatata hicicicic Su
Su
Su
Surg
r ery
ry
ry
ry; J.C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
o nicicicicicicicicick
J
Or
Or
Or
Or
Or
Orthththththththththththththththththththtr ogn
gn
gn
gn
gn
gnatatatatatatatatatatatathicicicicicicici Su
Su
Surg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
o nicicicicicicicicicicicicicicicicicicicicicicicicicick
Or
Or
Or
Orththththththth
r ogn
gn
gn
gn
g atatatatatathicicic Su
Su
Su
Su
S rg
r ery
ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
o nicicicicicicicicicicicicicicicicick
K
Or
Or
Orththth
r ogn
gn
gn
gn
g atatatathicicicicicicicici Su
Su
Su
Su
Su
Su
Su
Su
Su
S rg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
o nicicicicicicicicicick
Or
Or
Or
Orthththth
r o n
gn
gn
gn
gn
g atatatatata hicicicicicicicicicic Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
S rg
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ry
ry
ry
ry
ry
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ry
ry
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ry
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ry
r ; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C. Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
o nicicicicicicicicicicicicicicicicicicicicick
I, Frontal views
with smile before and after reconstruction.
J, Oblique facial views before and after
reconstruction. K, Profile facial views
before and after reconstruction.
• Figure 4-41, cont’d

131
CHAPTER 4  Hereditary, Developmental, and Environmental Influences on the Formation of Dentofacial Deformities
Prior to retreatment
After treatment
L
M
L, Occlusal views before and after orthodontics and orthognathic surgery. M, Lateral cephalometric
radiographs before and after reconstruction.
• Figure 4-41, cont’d 
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135

5
Orthodontic Considerations in
the Evaluation and Treatment
of Dentofacial Deformities
JEFFREY C. POSNICK, DMD, MD
• Orthodontic Treatment Philosophy
• The Biologic Basis for Orthodontic
Tooth Movement
• Periodontal Ligament Structure and Function
• Response of the Teeth and the Periodontium
to Normal Occlusal Function
• Orthodontic Tooth Movement
• Conclusions
of tooth moving appliances and attributed any
change back toward the original malocclusion
to ‘the wisdom teeth’ or ‘the lack of patient
cooperation wearing the removable retainer as
instructed.’ ”
Current issues in orthodontic therapy are, for the most
part, no longer just a matter of what attachments or
mechanical approaches to use.* Contemporary orthodon­
tics focuses on accurate diagnosis and a basic philosophy of
treatment to enhance facial aesthetics and to correct dys­
function. The role of orthognathic surgical interventions
and coordinated comprehensive dental rehabilitation to
achieve the most favorable outcome should always be
considered.110
Malocclusions result from a combination of environ­
mental influences and the patient’s morphogenetic heredi­
tary predisposition (see Chapter 4).1,11,15,18,43,44 The dental
alignment that naturally occurs in each individual is greatly
influenced by the baseline jaw relationships as well as by his
or her daily postural masticatory and airway function.† In
the presence of a dentofacial deformity, the mere orthodon­
tic movement of the teeth into a “better” interdigitation will
not establish normal jaw relationships nor will it correct the
head and neck dysfunctions that contribute to or result
from the malocclusion.147,157,179-181 The observed crowding
of the teeth generally reflects nature’s attempt to establish a
homeostatic balance among the available space in the alveo­
lus, the size of the teeth and the dental roots, the position
and size of the jaws, and the constant molding and balanc­
ing effects of the masticatory and facial musculature with
regard to daily function.6,146,147,162-165,182,183
Orthodontic Treatment Philosophy
In current clinical practice, orthodontic therapy is carried
out to provide an idealized occlusion, to enhance facial
aesthetics, and to contribute to the individual’s overall
health and self-image. Through manipulation of the peri­
odontal apparatus, orthodontic treatment has the potential
to not only improve occlusion and periodontal relationships
but to facilitate their maintenance over a lifetime. For those
individuals with dentofacial deformities, orthodontic treat­
ment is indispensable to remove dental compensations,
thereby allowing for the correction of the jaw relationships
while providing optimal occlusion and periodontal health.
Orthodontics has come a long way since 1972, when
Dr. T.M. Graber stated the following in the standard text­
book of the day:
“Orthodontic therapy can produce dire consequences
that will later require the services of the periodontist
or even the prosthodontist. The limitations of orthodontic
treatment are stringent. The [useful] role of tooth sacrifice
[and/or orthognathic surgery] must be recognized.
Traditionally, orthodontists had their patients wear
retaining appliances indefinitely after the removal
†References 50, 58, 59, 75, 76, 91, 93-97, 119, 127, 134-136, 141, 150-
152, 167, 213, 216, 229
*References 20, 22, 35, 45, 46, 48, 83, 87, 100, 115, 158, 171, 198, 207,
220-223, 226-228

136
SECTION 1  Basic Principles and Concepts
• Figure 5-1  A, Principal fiber bundles of the periodontal ligament on
the facial surface of a mandibular premolar (silver stain). B, Distribution
of faciolingual forces (arrows) around the axis of rotation (R) in a man­
dibular premolar. The periodontal ligament fibers are compressed in
areas of pressure (P) and taut in areas of tension (T). Part A from Glick­
man I: Clinical periodontology, ed 4, Philadelphia, 1972, W.B. Saun­
ders Company, Figures 2-3 and 2-8, pp 34 and 38, respectively.
A
R
B
P
T
P
T
The Biologic Basis for Orthodontic
Tooth Movement
Currently, there are a plethora of appliances than can
accomplish almost any desired change in the alignment of
the teeth.69,72 From a purely mechanical perspective, ortho­
dontists are trained in the techniques of tooth movement
with the goals of improving dental alignment in each jaw
and achieving “ideal” occlusion between the upper and
lower arches. The orthodontic movement of the teeth is
based on the principle that, if prolonged pressure is applied
to a tooth, movement will occur as the bone around the
tooth remodels. This is primarily a periodontal ligament
phenomenon. In the process, bone is selectively resorbed in
some areas and deposited in others. The bone that sur­
rounds the tooth responds to the applied force through
intermediate structures (periodontal ligaments), and the
objective is for the tooth to move without the loss of crestal
height or cortical plates while carrying its attachment appa­
ratus along with it. The whole socket must migrate along
with the tooth during this process.
When orthodontic therapy is used to move teeth outside
of a biologic envelope, extended treatment time, the poten­
tial for periodontal sequelae, and a less-than-ideal long-
term occlusion are the likely consequences.70,86,178 These
may occur as a result of the following: (1) attempts to
further compensate the position of the teeth toward the
skeletal disharmony and outside of the alveolar housing;
(2) dental (root) crowding within limited available alveolar
bone; or (3) ongoing nasal airway obstruction with an open
mouth posture and inadequate lip coverage of the
incisors.4,8,9,32,73,85,193
Periodontal Ligament Structure
and Function
Unless ankylosis is present, each tooth is connected to and
separated from the adjacent alveolar bone by a specialized
collagen supporting structure known as the periodontal liga­
ment (PDL) (Fig. 5-1). The PDL normally occupies a space
of approximately 0.5 mm around all parts of the tooth root.
The PDL is comprised of a network of parallel collagenous
fibers that insert into the cementum (i.e., the covering of
the root surface of each tooth) and then into a dense bony
plate (radiographically, this is called the lamina dura) that
is adjacent to each tooth within the alveolar bone. These
supporting PDL fibers are angulated between the root of
the tooth and adjacent bone; they attach apically on the
root and extend occlusally to the adjacent bone. Biome­
chanically, these angulated PDL fibers act as shock absorb­
ers by helping to resist forces that are applied to the tooth
during normal chewing function.
Within the periodontal ligament space, there are cel­
lular elements (i.e., mesenchymal cells, nerve endings, and
vessels) and interstitial fluid. The primary cellular elements
(i.e., mesenchymal cells) are thought to differentiate to form
the fibrocytes and the osteocytes. The collagenous elements
of the PDL are constantly being renewed and altered,
depending on the level of functional stress that they are
undergoing. The remodeling and recontouring of the alveo­
lar bone is a necessary component of orthodontic tooth
movement, and it is dependent on specialized cells (Fig.

137
CHAPTER 5  Orthodontic Considerations in the Evaluation and Treatment of Dentofacial Deformities
Interestingly, nature’s application of these light prolonged
forces on the teeth can also occur from maintained postur­
ing of the muscles of the lips, cheeks, and tongue as they
press against the teeth, thereby causing dental movement
and remodeling of the alveolar ridge. When postural forces
from the lip, cheek, or tongue are pathologic, they may
contribute to the classic dental compensations that are seen
with each specific pattern of developmental dentofacial
deformity.* These environmental forces may then be com­
pounded by iatrogenic orthodontic dental compensation
maneuvers to further affect periodontal health. For example,
consider the retroclination of the lower anterior teeth that
is seen with Class III skeletal patterns (Fig. 5-3) (see Chapter
20) or the proclination of the lower incisors that is seen with
skeletal Class II cases (Fig. 5-4) (see Chapter 19). In both
instances, negative periodontal sequelae may occur.
Orthodontic Tooth Movement
The Periodontal Ligament and Bone Response
to Sustained Orthodontic Force
The specific anatomic response to orthodontic forces is
dependent on the force magnitude. “Heavy” forces often
result in pain, necrosis of cellular elements within the PDL
(i.e., hyalinization), and remodeling with the resorption of
the alveolar bone that is being compressed (i.e., the hyalin­
ization zone). It may also result in the resorption of the root
apex, remodeling with the loss of crestal bone, and fenestra­
tions or dehiscence through the cortical plates. When light
and constant forces are applied to the tooth, there is compres­
sion without necrosis of the PDL elements and remodeling
of the tooth socket without significant irreversible necrosis.
As long as the tooth is being moved into adequate alveolar
bone and the forces are light, the root of the tooth is less
likely to resorb, and the alveolar crest height and cortical
plates are for the most part preserved.30 The objective of the
orthodontic movement of a tooth is to produce the desired
new tooth position as quickly as can be done, with as little
damage as possible to the tooth, the PDL, the alveolar bone,
and the adjacent teeth.
There are two major theories to explain the observed
process of orthodontic human tooth movement: the bioelec­
tric theory and the pressure-tension theory. The bioelectric
theory holds that the changes in bone metabolism that are
required to effectively move teeth and their sockets are
controlled by the electric signals produced when alveolar
bone bends and the crystalline structure is distorted. The
pressure-tension theory presumes that cellular changes
occur when pressure or tension is applied within the PDL
or tooth socket, which then produces chemical changes. The
pressure and tension that occur within the PDL result in
specific blood flow changes and the release of chemicals that
5-2). As part of the remodeling process, bone is removed
by osteoclasts that are thought to be derived from the mes­
enchymal cells. Cementum is removed by specialized cemen­
toclasts, which are also derived from mesenchymal cells.
Nerve endings attach to the PDL and to the blood vessels
that surround them. The nerve endings are effective for
proprioception and for the perception of pain. The intersti­
tial fluid found within the PDL space is derived from the
vascular network. It serves as a nutrient source, and it con­
tributes to the shock-absorbing mechanism to better with­
stand the physiologic forces as well as any pathologic forces
that are applied directly to the teeth.
Response of the Teeth and
the Periodontium to Normal
Occlusal Function
During normal chewing function, the teeth are subjected
to intermittent forces that are then transmitted to the peri­
odontal structures.55,88,89,92,118,192,209 When forces are applied
to a tooth, the load is dissipated by the periodontal liga­
ment and the interstitial fluid within the tooth socket.
These mechanisms allow a more limited force to then be
transmitted to the cortical bone that surrounds the tooth
socket (i.e., the lamina dura), which “bends” in response.
The term bending is used to describe the physiologic
response to normal masticatory forces. The bone bending
that occurs in response to normal (chewing) function is
thought to be an important stimulus to osseous regenera­
tion and repair. This intermittent but repetitive stress
loading allows for the modification of the bony architecture
as an adaptation to functional demands. If pressure against
the tooth is maintained (as opposed to being intermittent,
as when chewing), the interstitial fluid within the tooth
socket is expressed (i.e., pushed out) and the tooth itself is
displaced, thereby compressing the PDL directly against the
adjacent bone. This is perceived by the individual as being
quite painful, and, if the force is excessive and prolonged,
a different physiologic response occurs. This “trauma from
occlusion” is a response in which the remodeling of the
adjacent compressed bone occurs. A definition of the term
traumatic occlusion was first provided by Stillman in 1917.
He stated that traumatic occlusion is “a condition where
injury results to the supporting structures of the teeth by
the act of bringing the jaws into closed contacts.”171 The
definition given by the American Association of Periodon­
tics in 1986 is “an injury to the attachment apparatus as a
result of excessive occlusal force.”171 Primary occlusal trauma
involves excessive forces on a normal periodontium, and
secondary occlusal trauma is considered to have occurred
when normal forces are placed on a compromised peri­
odontium (see Chapter 6).
The intentional application of these principles is how
controlled orthodontic tooth movement occurs. The appli­
cation of light prolonged vector-controlled forces allows for
more or less predictable man-made movements of the teeth.
*References 50, 58, 75, 76, 91, 93-97, 119, 127, 134-136, 141, 150-152,
167, 213, 216, 229

138
SECTION 1  Basic Principles and Concepts
• Figure 5-2  A, Undermining resorption in a 12-year-old child. This is a view from a short-rooted premolar tooth.
The cementum that covers the root surface has not been broken, although the periodontal membrane is hyalin­
ized at the area of greatest pressure. A spicule of bone is being attacked from above and below, away from the
compressed PDM. B, Undermining resorption is taking place in a 39-year-old adult. No osteoclastic activity occurs
in the compressed PDM, but osteoclasts are at work on bundle bone that has been laid down previously from
above and below the area of greatest pressure. A, Thick cementum layer. B, Hyalinized periodontal ligament.
C and D, Frontal undermining bone resorption on both sides of the cell-free area. C, Tooth movement with light
forces. This image shows the pressure side during the period shortly after hyalinization. A, Root surface.
B, Remnants of cell-free, formerly hyalinized tissue. C, Large marrow space in alveolar bone. D, Direct bone
resorption. E, Compensatory bone formation in the marrow space as a response to bone resorption on the
side of the periodontal ligament. A courtesy K. Reitan from Graber TM: Orthodontics: principles and practice,
ed 3, Philadelphia, 1972, W.B. Saunders Company, Figure 10-5, p 496. B courtesy K. Reitan from Graber TM:
Orthodontics: principles and practice, ed 3, Philadelphia, 1972, W.B. Saunders Company, Figure 10-5, p 496.
C courtesy K. Reitan from Graber TM: Orthodontics: principles and practice, ed 3, Philadelphia, 1972, W.B.
Saunders Company, Figure 10-6, p 497.
A
B
C
B
A
D
C
C
B
A
D
E

139
CHAPTER 5  Orthodontic Considerations in the Evaluation and Treatment of Dentofacial Deformities
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• Figure 5-3  A 34-year-old man arrived for the evaluation of a long-standing jaw deformity with malocclusion, chronic obstructive nasal breathing,
and periodontal issues. Since his early childhood years, he was known to have a maxillary deficiency with a relative mandibular excess growth
pattern. The family elected a camouflage orthodontic approach that included four bicuspid extractions and the introduction of dental compensa­
tion in an attempt to neutralize the occlusion when he was 10 to 15 years old. He was a forced mouth breather as a result of the associated
increased nasal airway resistance. He underwent septoplasty when he was 20 years old, but this did not result in significant improvement. His
general dentist confirmed labial bone loss and gingival recession of the mandibular anterior and maxillary posterior dentition. He was referred to
this surgeon, and a comprehensive orthognathic and dental rehabilitation approach was recommended. Consultations with a periodontist, an
orthodontist, and an ear, nose, and throat specialist were carried out. The patient was confirmed to have residual deviation of the septum and
enlarged inferior turbinates, which explained the continued difficulty that he had with breathing through his nose. A degree of root resorption of
the anterior dentition was confirmed. The need for gingival grafting to attain improved root coverage and to generate a wider band of attachment
was recommended (i.e., teeth nos. 3, 11, 14, 19, 20, 23 through 26, 29, and 30). This will be followed by the orthodontic removal of dental
compensation and then orthognathic and intranasal procedures to improve long-term dental health, to enhance facial aesthetics, and to open the
upper airway. A, Frontal facial and occlusal views before retreatment. B, Profile facial view and lateral cephalometric radiograph before retreatment.
C, Panorex radiograph with retreatment in progress.
C
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