Lecture 6 correction of dentofacial deformities

 Epidemiologic surveys demonstrate that a large percentage of the United
States' population has a significant malocclusion. Very little data describe
the exact prevalence of significant skeletal facial deformity.
 This information can be extrapolated from studies that have evaluated the
prevalence of severe malocclusion.
 The National Health and Nutrition Examination Survey (NHANES III)
conducted from 1989 to 1994 obtained a sample of 14,000 individuals ages
8 through 50 that roughly approximates the general U.S. population.
 In this study, information was collected describing overjet/reverse overjet,
vertical overlap (deep bite and open bite) , and posterior crossbites I It can
be assumed that patients with extreme values in each of these categories
have underlying facial deformities.
2

 Because many patients have dental compensations for
skeletal growth abnormalities (described later in this
chapter) , this study likely underestimates the severity of
skeletal abnormalities.
 This type of data combined with other criteria that clearly
define the most severe characteristics of a malocclusion,
such as overjet versus crowding, can help to approximate
more clearly the prevalence of skeletal abnormality that
may require surgical correction as part of the treatment
for malocclusion.
4

 It appears that about 2% of the u.s. population has
mandibular deficiency and/or vertical maxillary excess
that is severe enough to be considered handicapping.
 Other abnormalities and their percentage of prevalence
in the population include mandibular excess and/or
maxillary deficiency, 0.3%; open bite, 0.3%; and
asymmetry, 0.1 % .
 Therefore, it appears that approximately 2.7% of the U.S.
population may have a dentofacial deformity contributing
to malocclusion that will require surgical treatment for
correction.
5

 Historically, treatment of malocclusions, even those
associated with dentofacial deformities, has been aimed
at correction of dental abnormalities, with little attention to
the accompanying deformity of the facial skeleton.
 In the last 60 years, surgical techniques have been
developed to allow positioning of the entire midface
complex, mandible, or dentoalveolar segments to any
desired position.
 The combining of surgical and orthodontic procedures for
den to facial deformities has become an integral part of
the correction of malocclusions and facial abnormalities.
6

 Malocclusion and associated abnormalities of the skeletal
components of the face can occur as a result of a variety of
factors, including inherited tendencies, prenatal problems,
systemic conditions that occur during growth, trauma, and
environmental influences.
 Although it is not within the scope of this book to present a
detailed discussion of facial growth, an understanding of basic
principles as they relate to the development of dentofacial
deformities is essential. Enlow and Han's Essentials of Facial
Growth should be reviewed for a more complete discussion of the
principles of facial growth.
7

 The development of proper craniofacial form and function is a
complex process affected by many factors.
 In the area of the craniofacial complex, areas exist that appear to
have their own intrinsic growth potential, including the
sphenooccipital and sphenoethmoidal synchondroses and the
nasal septum.
 In addition, the majority of growth of the bones of the face occurs
in response to adjacent soft tissue and the functional demands
placed on the underlying bone. These soft tissue influences
include the nasal, oral, and hypopharyngeal airway; facial
muscles; and muscles of mastication.
8

 The general direction of normal growth of the face is downward
and forward with lateral expansion.
 The maxilla and the mandible appear to grow by remodeling or
differential apposition and resorption of bone, producing changes
in three dimensions.
 Enlow and Hans describe this phenomenon as area relocation,
with the maxillary-mandibular complex enlarging in the downward
and forward direction as an "expanding pyramid".
 The direction and amount of growth characterize an individual's
growth pattern. Alterations in the pattern of growth or in the rate
at which this growth occurs may result in abnormal skeletal
morphology of the face and an accompanying malocclusion.
9

A, Mandibular growth resulting from apposition and resorption of bone. Primary areas of bony
apposition include superior surface of alveolar process and posterior and superior surfaces
of mandibular ramus.
B, Forward and downward growth of nasal complex and maxilla in "expanding V “ Resorption
of bone at superior surface of palate occurs Simultaneously with apposition at inferior
surfaces of palate and alveolar processes. In addition, growth in posterior area of maxilla
results in downward and forward expansion of maxilla. 10

 Genetic influence certainly plays a role in dentofacial
deformities.
 Patterns of inheritance, such as a familial tendency toward
aprognathic or deficient mandible, are often seen in a patient
with a dentofacial deformity.
 However, the multifactorial nature of facial development
precludes the prediction of an inherited pattern of a particular
facial abnormality.
11

 Abnormal facial growth and associated malocclusions are
sometimes associated with congenital abnormalities and
syndromes. Some of these syndromes such as hemifacial
microsomia and mandibulofacial dysostosis (Treacher Collins
syndrome) are related to embryonic abnormalities of neural
crest cells.
 Other congenital abnormalities affecting jaw growth include
cleft lip and palate and craniosynostosis (premature fusions
of craniofacial sutures) .
 Facial growth abnormalities may be caused by maternal
systemic influences such as fetal alcohol syndrome, which
may result in hypoplasia of midface structures.
12

 Environmental influences also play a role in the
development of dentofacial deformities. As early as the
prenatal stage, A intrauterine molding of the developing
fetal head may result in a severe mandibular deficiency.
 Abnormal function after birth also may result in altered
facial growth because soft tissue and muscular function
often influence the position of teeth and growth of the
jaws. Abnormal tongue position or size can affect the
position and growth of the maxilla and mandible.
13

A, Tongue asymmetry with
unilateral hypertrophy.
B, Resulting unilateral open bite.
14

 Respiratory difficulty, mouth breathing, and abnormal tongue
and lip postures can adversely influence facial growth.
 Trauma to the bones of the face can result in severe
abnormalities of the facial skeleton and the occlusion.
 In addition to the abnormality that occurs as an immediate
result of trauma, further effects on the development of facial
bones may occur. In the case of temporomandibular joint
(TMJ) trauma in a growing child, significant restriction of jaw
function may occur as a result of scarring or bony/fibrous
ankylosis.
 Subsequent alteration of growth may result with deficient or
asymmetric mandibular growth
15

Condylar trauma at
an early age
resulting in
restricted jaw
function and
subsequent
deficient and
asymmetric
mandibular growth.
A, Profile view.
B, Occlusion with
right side anterior
open bite due to
decreased growth in
the left mandibular
ramus area.
C, Radiograph of
right condyle
and ramus (normal) .
D , Left side with
decreased growth.
16

 In the past, individual practitioners often treated patients with
dentofacial deformities. Some patients have been treated with
orthodontics alone, with a resultant acceptable occlusion but a
compromise in facial esthetics.
 Other patients have had surgery without orthodontics in an
attempt to correct a skeletal deformity, which resulted in improved
facial esthetics but a less than ideal occlusion.
 In addition to orthodontic and surgical needs, these patients often
have many other problems requiring periodontic, endodontic,
complex restorative, and prosthetic considerations.
17

 Many areas of dental practice, in addition to orthodontics
and surgery, must be integrated to address the complex
problems of patients with dental deformities.
 This integrated approach, used throughout the
evaluation, presurgical, and postsurgical phases of
patient care, provides the best possible results for these
patients
18

 The most important phase in patient care centers on
evaluation of the existing problems and definition of
treatment goals.
 At the initial appointment a thorough interview should be
conducted with the patient to discuss the patient's
perception of the problems and the goals of any possible
treatment.
 The patient's current health status and any medical or
psychological problems that may affect treatment are
also discussed at this time.
19

 The involved orthodontist and oral and maxillofacial surgeon
should conduct a thorough examination of facial structure,
with consideration of frontal and profile esthetics.
20

 Evaluation of facial esthetics in the frontal view should
assess the presence of asymmetries and evaluate overall
facial balance.
 The evaluation should include assessment of the position
of the forehead, eyes, infraorbital rims, and malar
eminences; configuration of the nose, including the width
of the alar base; paranasal areas; lip morphology;
relationship of the lips to incisors; and overall proportional
relationships of the face in the vertical and transverse
dimensions.
21

Normal facial proportions.
A, Representation of proportional relationships of full-face view. Relationships of medial
intercanthal distance, alar base width, and lip proportions to remainder of facial structures
are demonstrated.
B, Normal profile proportions demonstrates relationships of upper, middle, and lower thirds
of face and proportional relationships of lip and chin morphology within lower third of face.
22

 The profile evaluation allows an assessment of the
anteroposterior and vertical relationships of all components
of the face. The soft tissue configuration of the throat should
also be evaluated.
 Photographic documentation of the pretreatment condition of
the patient should be a standard part of the evaluation.
 Video and digital computerized images have been introduced
over the past decade as an additional aid in evaluating facial
morphology.
23

 A complete dental examination should include assessment of
dental arch form, symmetry, tooth alignment, and occlusal
abnormalities in the transverse, anteroposterior, and vertical
dimensions.
 The muscles of mastication and TMJ function should also be
evaluated. A screening periodontal examination, including
probing, should assess the patient's hygiene and current
periodontal health status.
 Impressions and a bite registration for dental cast
construction and evaluation should also be obtained at this
time.
24

 Lateral cephalometric and panoramic radiographs are
routinely used in the patient evaluation and are an
important part of the initial assessment.
 The cephalometric radiograph can be evaluated by
several techniques to aid in the determination of the
nature of the skeletal abnormality.
25

A, Lateral cephalometric radiograph.
B, Tracing of lateral cephalometric head film, with
landmarks identified for evaluating facial, skeletal, and
dental abnormalities using system of cephalometries for
orthognathic surgery 26

 An important note, however, is that cephalometric
radiographs are only a part of the evaluation process;
they are used as adjunctive diagnostic tools in the clinical
assessment of the patient's facial structure and
occlusion.
 Other radiographic images may be helpful in evaluating
patients for surgical correction. These may include
posteroanterior facial films, TMJ images when indicated,
and conventional and cone-beam computed tomography
28

A, Cone-beam computed tomography scan clearly demonstrating bone
deformity in three dimensions with detailed view of skeletal components,
tooth root positioning, and location of the inferior alveolar nerve.
B, Stereolithic model.
29

 In difficult, complex cases, it may be helpful to obtain a
stereolithic three-dimensional model constructed from computed
tomography scan data.
 Computerized digital technology is currently available that helps
to integrate the cephalometric data with digital images of the face
to improve evaluation of the relationship of the underlying facial
skeleton and overlying soft tissue.
 After careful clinical assessment and evaluation of the diagnostic
records, a problem list and treatment plan should be developed
that combines opinions from all practitioners participating in the
patient's care, including the orthodontist, oral and maxillofacial
surgeon, periodontist , and restorative dentist.
30

Periodontal Considerations
 As the first step in treatment, gingival inflammation must be
controlled and the patient's cooperation ensured.
 In patients who are unwilling or unable to clean their teeth
properly before the placement of orthodontic appliances, oral
hygiene procedures will be even less effective when
complicated by orthodontic band placement.
31

 Periodontal therapy includes oral hygiene instruction,
scaling, and root planing; in certain instances, flap
surgery to gain access for root planing may be necessary
to provide proper tissue health.
 Whenever possible, it is desirable to delay
comprehensive treatment until adequate patient
compliance and control of inflammation are achieved.
32

 As a result of the periodontal examination findings and
proposed orthodontic and surgical plan, mucogingival
surgery is often accomplished during this initial phase of
therapy to provide a zone of attached keratinized tissue that
is more resistant to potential orthodontic and surgical trauma.
 Soft tissue grafting is indicated in areas that have no
keratinized gingiva or where only a thin band of keratinized
tissue with little or no attachment is found when an increase
in tissue trauma is likely.
 Such trauma to these areas includes labial orthodontic
movement of teeth or a surgical procedure such as an
inferior border osteotomy or segmental osteotomies in
interdental areas.
33

A, Presurgical appearance of gingival tissue labial to
lower anterior teeth. Inadequate area of attachment
and keratinization is visualized.
B, Significant improvement in attachment and
keratinization of labial gingival tissue after gingival
grafting.
34

 During the presurgical restorative phase, the patient is evaluated for
carious lesions and faulty restorations. Teeth should be evaluated
endodontically and periodontally for restorability, and any
nonrestorable teeth should be extracted before surgical intervention.
 All carious lesions must be restored early in the presurgical treatment
phase. Existing restorations must function for 18 to 24 months during
the orthodontic and surgical treatment phases, requiring that more
durable restorative materials (i.e . , amalgam and composite resin) be
used, even though they may be replaced during the definitive
postsurgical treatment phase.
 It is wise to delay final restorative treatment until the proper skeletal
relationships are achieved and the finishing orthodontics is completed.
35

 In the edentulous or partially edentulous patient, particular
attention is paid to residual ridge shape and contour in
denturebearing areas.
 The distance between the maxillary tuberosity, posterior
mandible, and ramus areas must be evaluated to ensure that
adequate space is present for partial or complete dentures.
 Teeth that serve as removable partial denture abutments
should be evaluated for potential retentive undercuts.
 If minor orthodontic movement can enhance undercuts, this
information is conveyed to the orthodontist.
36

 Obviously, not all malocclusions require correction with surgery When the
skeletal discrepancy is minimal and orthodontic compensation does not
adversely affect dental or facial esthetics or posttreatment stability, orthodontic
treatment alone may be the treatment of choice.
 However, in some cases an adequate occlusal relationship cannot be achieved
because of the skeletal discrepancy; some patients may be treated with
orthodontic compensation for a skeletal abnormality, resulting in an adequate
occlusion but poor facial or dental esthetics or a poor long-term prognosis for
posttreatment retention. These patients should be considered for surgery
combined with orthodontic treatment.
37

 Treatment of the stable adult deformity can be started without delay,
but questions often arise about how best to manage the growing child
who is identified as having a developing dentofacial deformity.
 If the facial pattern is favorable and Significant growth potential
remains, growth modification with techniques such as functional
appliance therapy or headgear may be the preferred approach.
 For patients with unfavorable growth patterns or severe skeletal
abnormalities or who are unwilling to undergo attempts at growth
modification, surgery is usually the preferred treatment.
 As a general guideline, orthognathic surgery should be delayed until
growth is complete in patients who have problems of excess growth,
although surgery can be considered earlier for patients with growth
deficiencies.
38

 Undesirable angulation of the anterior teeth occurs as a
compensatory response to a developing dentofacial
deformity.
 For example, a patient with maxillary deficiency and/or
mandibular excess often has dental compensation for the
skeletal abnormality with flared upper incisors and retracted
or retroclined lower incisors.
39

A, Class III skeletal malocclusion with maxillary deficiency and
mandibular excess.
B, Dental compensation includes retroclined lower incisors and proclined
upper incisors.
C, Facial profile. 40

 Dental compensations for the skeletal deformity are
corrected before surgery by orthodontically repositioning
teeth properly over the underlying skeletal component,
without considerations for the bite relationship to the
opposing arch.
 This presurgical orthodontic movement accentuates the
patient's deformity but is necessary if normal occlusal
relationships are to be achieved when the skeletal
components are properly positioned at surgery.
41

D , After initial orthodontic treatment before surgery.
E , Dental compensation are removed with proclination of lower
incisors and retroclination of upper incisors, which obviously
increases the severity of malocclusion and facial discrepancy.
F, Facial profile at this stage.
42

 The surgical treatment then results in an ideal
position of the skeletal and dental components.
43

G, Surgical correction with posterior positioning of mandible and
advancement of maxilla.
H, Ideal occlusion.
I, Facial profile after treatment is complete.
44

 The opposite dental compensation may occur in
maxillaryprotrusion or mandibular deficiency.
 Again, the decompensation is aimed at improving
angulation of teeth over underlying bone, after which
skeletal problems are corrected.
45

A, Class II occlusion with compensation demonstrating
proclination of lower incisors and upright upper incisors.
B, After orthodontic decompensation.
C, After surgical correction with mandibular advancement.
46

 The essential steps in orthodontic preparation are to align the
arches individually, achieve compatibility of the arches or
arch segments, and establish the proper anteroposterior and
vertical position of the incisors.
 The amount of presurgical orthodontics can vary, ranging
from appliance placement with minimal tooth movement in
some patients to approximately 12 to 18 months of appliance
therapy in those with severe crowding and incisor
malposition.
47

 As the patient is approaching the end of orthodontic
preparation for surgery, it is helpful to take impressions and
evaluate progress models for occlusal compatibility.
 Minor interferences that exist can be corrected easily with
arch wire adjustment and significantly enhance the
postsurgical occlusal result.
 After any final orthodontic adjustments have been made,
large stabilizing arch wires are inserted into the brackets,
which provide the strength necessary to withstand the forces
resulting from intermaxillary fixation (lMF) and surgical
manipulation.
48

 After the completion of the presurgical periodontics,
restorative dentistry, and orthodontics, the patient returns to
the oral-maxillofacial surgeon for final presurgical planning.
The evaluation completed at the initial patient examination is
repeated. The patient’s facial structure and the malocclusion
are reexamined.
 Presurgical digital photographs and conventional radiographs
or CT scans, and impressions or digital scans of the dentition
are obtained in preparation for developing the final surgical
plan.
49

 When using a traditional model surgery planning
technique, presurgical models, a centric relation bite
registration, and face-bow recording for model mounting
are completed. Model surgery on a duplicated set of
presurgical dental casts determines the exact surgical
movements necessary to accomplish the desired
postoperative occlusion
50

 Model surgery used to determine direction and distance of
surgical movement necessary to achieve desired
postoperative occlusion and facial esthetics.
A, Casts mounted on semiadjustable articulator.
B, Repositioning of maxillary cast using precision
measuring instrument. Distances of model surgical
movements are coordinated between desired facial esthetics
and movements necessary to create ideal postoperative
occlusion.
C , Maxillary cast remounted on semiadjustable articulator
after precision movements have been completed and
verified. Intraocclusal wafers are constructed on this final
occlusal setup for use at time of surgery to align
osteotomies and dental segments into desired postsurgical
position.
51

 The change in facial appearance can be demonstrated
with the use of computer technology by superimposing
digital images of the patient’s profile over bone
landmarks obtained from the cephalometric radiograph.
 The bone structures are then manipulated to duplicate
the bone movements desired at the time of surgery.
 The computer can then produce a digital image that
represents the facial aesthetic result produced by the
associated facial skeletal change
53

Computerized imaging for
dentofacial surgical treatment
planning. Digital image is obtained
and placed in computer memory.
Landmarks from cephalometric
tracing are superimposed over
digital image of face. A, Portions of
cephalometric tracing can be
moved to duplicate the anticipated
surgical movements. The computer
then manipulates the image to
depict soft tissue
changes. Digital images displayed
on the computer monitor shows
predicted facial changes (Quick
Ceph Image System) .
B, View shows presurgical and
estimated final images that would
result from anticipated surgical
procedure (in this case, maxillary
superior repositioning and chin
advancement).
54

 The advantage of using this type of technology is the
ability to predict more accurately the facial changes that
may result from a particular surgical correction.
 The facial images are also more easily evaluated by
patients, allowing them to assess the predicted results
and provide input into the surgical treatment plan.
55

 One disadvantage of this technology is that the
predictions are limited to 2D predictions showing only the
lateral profile.
 Another disadvantage of the technology is related to the
inability of the computer to predict accurately every type
of surgical change for every patient.
 Different muscle tone and skin thicknesses and variable
soft tissue responses to bone change, for example, make
it impossible for the computer to predict each individual
variation precisely.
56

 Recent advances in imaging technology and 3D computer
planning have improved the precision in surgical correction of
complex dentofacial deformities.
 Conventional CT or CBCT data are combined with laser,
optical, or CT scans of the dentition, to produce a
computerized model of the skeletal and occlusal
abnormalities.
 The planned osteotomies can then be designed and surgical
movements created to reposition the skeletal and occlusal
components into the corrected positions
57

(A–B) Lateral and posteroanterior
views of skeletal and dental
components of a dentofacial
deformity, including vertical
maxillary excess and mandibular
excess with class III open bite
occlusion. (C–D) Views of planned
skeletal changes to correct the
deformity. (E) View of the inferior
portion of the mandible showing
the yaw deformity (twisting of the
posterior mandible to the right
side) and (F) correction of
asymmetry.
58

(G) Splint designed to
guide positioning of
the segments during
surgery and numeric
measurement of
changes that will
occur during surgery.
(H) Computer image
of splint.
59

 This type of surgical planning provides an improved
understanding of the bone movements required at surgery.
The potential difficulty with bone interference, the need for
possible bone grafting and recontouring required to achieve
symmetry can all be clearly visualized.
 The splint can also be designed using 3D computer
technology with splint construction completed using computer
aided design and computer aided manufacturing (CAD-CAM)
rapid prototyping.
 The ability to use 3D technology to predict facial aesthetic
changes is also emerging. Digital photographs are
superimposed on the 3D CT data and a virtual model of the
face is constructed.
60

 Movement of the skeletal components produces soft tissue
changes that can then be visualized in three dimensions.
 Although the precision of the predictions has not been
studied extensively, this technology will continue to improve
and provide useful information to doctors and patients.
 After completion of the conventional or 3D virtual model
surgery and facial imaging predictions, the orthodontist and
the general dentist are often consulted to ensure that the
predicted occlusal result is acceptable to all practitioners
involved in the patient’s treatment.
 Any orthodontic or restorative changes necessary to improve
postsurgical position should be planned at this time.
61

 Dentofacial abnormalities frequently can be treated by
isolated procedures in the mandible or maxilla and
midface area. Because abnormalities can obviously
occur in the maxilla and the mandible, surgical correction
frequently requires a combination of surgical procedures.
 The following sections describe a variety of surgical
procedures completed as isolated osteotomies or as
combination procedures.
62

 Excess growth of the mandible frequently results in an abnormal
occlusion with Class III molar and cuspid relationships and a
reverse overjet in the incisor area.
 An obvious facial deformity may also be evident. Facial features
associated with mandibular excess include a prominence of the
lower third of the face, particularly in the area of the lower lip and
chin in the anteroposterior and vertical dimensions.
 In severe cases the large reverse overjet may preclude the
patient's ability to obtain adequate lip closure without abnomlal
strain of the orbicularis oris muscles.
63

 Mandibular excess was one of the first dentofacial
deformities recognized as being best treated by a
combination of orthodontics and surgery.
 Although surgical techniques for correction of mandibular
excess were reported as early as the late 1800s, widespread
use of currently acceptable techniques began in the middle of
this century.
 Early techniques for treatment of mandibular prognathism
dealt with the deformity by removing sections of bone in the
body of the mandible, which allowed the anterior segment to
be moved posteriorly.
64

Body ostectomy with resection of portion of body of
mandible followed by posterior repositioning of
anterior segment.
A, Preoperative view.
B, Postoperative view. 65

 When the reverse overjet relationship is isolated to the
anterior dentoalveolar area of the mandible, a subapical
osteotomy technique can be used for correction of
mandibular dental prognathism.
 In this technique, bone is removed in the area of an
extraction site of a premolar or molar tooth, and the anterior
dentoalveolar segment of the mandible is moved to a more
posterior position.
 Although these procedures are rarely used, they are
occasionally perfomled in cases with unusual arch forms in
combination with edentulous spaces.
67

Anterior mandibular subapical osteotomy.
A, Removal of premolar teeth and bone in area of extraction
sites.
B, After separation, anterior dentoalveolar segment is
repositioned posteriorly, extraction sites are closed, and
anterior reverse overjet relationship is corrected. 68

 In the early 1950s, Caldwell and Letterman popularized an
osteotomy performed in the ramus of the mandible for the
correction of mandibular excess.
 In this technique the lateral aspect of the ramus is exposed
through a submandibular incision, the ramus is sectioned in a
vertical fashion, and the entire body and anterior ramus
section of the mandible are moved posteriody, which places
the teeth in proper occlusion
69

Extraoral approach for vertical ramus osteotomy.
A, Submandibular approach to lateral aspect of ramus showing vertical osteotomy from
sigmoid notch area to angle of mandible.
B, Overlapping of segments after posterior repositioning of anterior portion of mandible.
Proximal segment containing condyle is overlapped on lateral aspect of anterior portion of
ramus.
70

 The proximal segment of the ramus (i.e., the portion
attached to the condyle) overlaps the anterior segment,
and the jaw is stabilized during the healing phase with
wiring of the bone segments combined with jaw
immobilization using IMF. The extraoral approach is
rarely used.
 A similar technique is performed with an intraoral incision
and an angulated oscillating saw.
71

Intraoral technique
for vertical ramus
osteotomy through
use of angulated
oscillating saw.
72

 The design of the osteotomy is identical to that performed
through an extraoral incision. The bone segments can be
stabilized using IMF, with or without direct wiring of the
segments or using rigid fixation with bone plates or
screws, eliminating the need for IMF.
 The advantages of the intraoral technique include
elimination of the need for skin incision and decreased
risk of damage to the mandibular branch of the facial
nerve.
73

Case report of mandibular excess.
A and B, Preoperative facial esthetics demonstrates typical features of
Class III malocclusion resulting from mandibular excess.
C and D , Presurgical occlusal photographs.
E and F, Diagram of intraoral vertical ramus osteotomy with posterior
positioning of mandible and rigid fixation.
75

Postoperative frontal and profile view of patient seen in A and B.
G and H , Postoperative occlusion seen in I and J .
K and L show preoperative and postoperative radiographs.
77

 Another popular technique for correction of mandibular
prognathism is the bilateral sagittal split osteotomy (BSSO)
first described by Trauner and Obwegeser and later modified
by Dalpont, Hunsick, and Epker
 The BSSO is accomplished through a transoral incision
similar to that for the intraoral vertical ramus osteotomy The
osteotomy splits the ramus and posterior body of the
mandible in a sagittal fashion, which allows setback or
advancement of the mandible.
78

Sagittal split osteotomy.
Ramus of mandible is
divided by creation of
horizontal osteotomy on
medial aspect and
vertical osteotomy on
lateral aspect of
mandible.
These are connected by
anterior ramus
osteotomy Lateral cortex
of mandible is then
separated from medial
aspect, and mandible can
be advanced or set back
for correction of
mandibular deficiency or
excess, respectively.
79

 The telescoping effect in the area of the osteotomy produces
large areas of bony overlap that have the flexibility necessary
to move the mandible in several directions.
 The BSSO technique has become one of the most popular
methods for treatment of mandibular deficiency and
mandibular excess.
 Disadvantages include potential trauma of the inferior
alveolar nerve, with subsequent decreased sensation in the
area of the lower lip and chin during the immediate
postoperative period. This may be permanent.
80

Lecture 6 correction of dentofacial deformities

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