Download Applying transverse genioplasty for facial asymmetry and profile

Applying transverse genioplasty for facial asymmetry and profile
improvement－case report
YI-JYUN CHEN1,3
TSUI-HSIEN HUANG1,3
CHIH-YU PENG1,3
CHIA-TZE KAO2,3
1
Institute of Stomatology, College of Oral Medicine, Chung Shan Medical University, Taichung, Taiwan, ROC.
Institute of Oral Material Science, College of Oral Medicine, Chung Shan Medical University, Taichung, Taiwan, ROC.
3
Department of Dentistry, Chung Shan Medical University Hospital, Taichung, Taiwan, ROC.
2
An 18-year-old healthy man with marked facial and dental asymmetry due to unilateral mandibular
condylar hyperplasia was treated with pre-adjusted fixed appliance therapy combined with transverse
genioplasty. The total treatment time was 28 months. Although the compromised treatment did not
exactly correct the asymmetry, a more-balanced proportion of facial features and a better profile were
achieved. The mentalis muscle tone was also relieved, presenting a smooth labiomental fold with a
satisfying outcome. （J Dent Sci, 3(2)：108-116 , 2008）
Key words: facial asymmetry, transverse genioplasty, labiomental fold, profile.
Most of the time, people view themselves from
the front rather than from other aspects1, and it is also
easier for patients and orthodontists to identify facial
asymmetry from a frontal view2-5. For an adult patient
with a skeletal Class III malocclusion and a midline
deviation, combined surgical-orthodontic therapy is
often the treatment of choice because of its satisfying
outcome and stability6. Camouflage treatment with
selective extractions is usually considered only for
borderline patients. A Class III malocclusion is caused
by any combination of deficient maxillary growth and
excessive mandibular growth. However, injury to the
condylar region can result in growth arrest, and
consequently a characteristic distortion of the mandibular form producing facial asymmetry7.
Many schematic diagrams of the “ideal” position
of the chin as described by Ricketts8, Steiner9,
Burstone10, and Holdway11 are all discussed in the
horizontal anteroposterior direction; therefore, genioplasty has become one of the best choices of
surgical procedures for correcting chin deformities12-14.
Received: February 18, 2008
Accepted: May 13, 2008
Reprint requests to: Dr. Chia-Tze Kao, Institute of Oral Material Science,
Chung Shan Medical University, No. 110, Chien-Kuo
North Road, Section 1, Taichung, Taiwan 40201,
ROC.
108
In contrast, transverse genioplasty is an option for
correcting mandibular asymmetry12; and although it is
less effective for overall facial balance, fewer risks are
involved14.
Sometimes, the treatment plan consists of
orthodontic treatment combined with compromised
minor surgery rather than the most ideal surgical
procedures, or even no surgery is involved15-17. The
ultimate benefit to the patient has always been the
primary concern of clinicians providing coordinated
orthodontic and orthognathic surgical treatment18.
The present case report describes an example of
orthodontic compensatory treatment combined with
transverse genioplasty of an adult patient with a class
III malocclusion and facial asymmetry. Transverse
genioplasty decreased the degree of facial asymmetry
and significantly improved the facial profile by
simultaneously relieving the mentalis muscle tone.
CASE PRESENTATION
An 18-year-old male presented with the chief
complaint of “I don’t like my asymmetric chin
position which makes me look quite different from
other people” (Figure 1A). His medical history
showed no contraindication to orthodontic therapy.
According to the interview data, he had received a
J Dent Sci 2008‧Vol 3‧No 1
Transverse genioplasty for facial profile improvement
Figure 1. An 18-year-old male patient with a class III malocclusion and dentofacial midline deviation
(A, B). (A, C) The mentalis hyperfunction has had a detrimental effect on the facial esthetics in both
frontal and profile views. (D) The asymmetry is the result of unilateral condylar hypoplasia.
traumatic injury to the left side of the chin at 7 years
of age with a residual scar (Figure 2); a family history
of mandibular prognathism was denied. A facial
examination showed constricted mentalis muscle tone
(mentalis muscle hypertension) and an anterior bulge
of the labiomental skin, with the chin deviated to the
left side. There was a 5-mm deviation of the chin
button from the facial midline. On an intraoral
examination, the teeth were well aligned in both
arches, and a huge amalgam restoration was found on
J Dent Sci 2008‧Vol 3‧No 1
the mandibular first molar, which also revealed an
edge-to-edge incisor relationship (Figure 1B). The
facial asymmetry originated from the cranial base,
maxilla, and mandible (Figure 3A). Furthermore, the
asymmetrical mandible body length and ramus height
(Figures 1D, 3A) resulted in a class III malocclusion
on the right side with a buccal crossbite between the
lower left canine and lower left first premolar
(Figure 1B), with both dental midlines deviating to the
left. The cephalometric analysis (Figure 3B, Table 1)
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Y.J. Chen, T.H. Huang, C.Y. Peng, et al.
Figure 2. A scar on the left side of the patient’s chin.
confirmed the skeletal class III pattern (with an ANB
of -1) with bimaxillary dental protrusion (with a
U1-L1 angle of 108°) and an average mandibular
plane angle (FMA) of 28°. He was diagnosed as
having an Angle’s Class III malocclusion with incisor
edge-to-edge occlusion, a dental midline deviation, an
asymmetric skeletal Class III jaw base relationship,
and a normal mandibular plane angle.
Treatment plan
During consultations with the patient and his
parents, a treatment plan was devised based on the
concept of non-extraction orthodontic treatment
involving compensatory dental changes with
genioplasty for the skeletal discrepancy. The treat-
ment plan consisted of the following stages: (1)
achievement of Class I molar occlusion and normal
incisor relationships with 0.022-inch-slot pre-adjusted
edgewise appliances and inter-arch asymmetrical
mechanics; (2) a deferred surgical procedure to
identify the cessation of skeletal growth using serial
cephalometric radiographs; (3) extraction of the right
maxillary and mandibular third molars; and (4)
retention of the upper and lower removable retainers.
Treatment progress
At the age of 18 years and 5 months, the
pre-adjusted 0.022-inch-slot edgewise appliances
were put in place. After the initial leveling was
accomplished, the maxillary anterior teeth were
Figure 3. Superimposition of cephalometric tracings before and after treatment.
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Transverse genioplasty for facial profile improvement
Table 1. Summary of the cephalometric analysis
Measurement
Norm
Initial
Finish
SNA
82°
84°
84°
SNB
80°
85°
83°
ANB
2°
-1°
1°
SND
76°~77°
83°
81°
U1-UA
4 mm
13 mm
13 mm
U1-UA
22°
38°
41°
L1-NB
4 mm
10 mm
9 mm
L1-NB
25°
35°
36°
0 mm
1 mm
Pog-NB
U1-L1
131°
108°
100°
OccI-SN
14°
10°
9°
GoGn-SN
32°
30°
30°
Max.L(A’-C’)
50 mm
48 mm
48 mm
Mand.L(B’-D’)
50 mm
52 mm
51 mm
ALFH(A’-B’)
67 mm
68 mm
PLFH(C’-D’)
50 mm
50 mm
Aver ALFH=(ALFH+FLFH)/2
58.5
59
FMA
31±5°
28°
32°
IMPA
94±6°
98°
99°
FMIA
55±6°
54°
49°
Wits(A/B to OccI. PI)
-1.4±2.6 mm
mix.: -0.8~1.5
-7 mm
-3.5 mm
retracted with a 0.019 × 0.025-inch rectangular
stainless steel arch wire with vertical loops as hooks
between the maxillary central and lateral incisors, and
a mandibular 0.019×0.025-inch rectangular stainless
steel arch wire for further alignment. The lower arch
wire with a reverse curve of Spee was used to tip back
the molars in order to achieve a better molar
relationship. After a 7-month period of leveling, the
right lower and upper third molars were sequentially
extracted. The malocclusion correction was done and
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was completed using inter-arch asymmetric mechanics
and vertical elastics. After 25 month of edgewise
treatment, Class I incisor and molar relationships with
good buccal segment interdigitation had been
achieved (Figure 4), and further consultation focused
on surgical correction of the facial asymmetry
(Figure 5). After an extraoral facial analysis, a
transverse sliding osteotomy shift to the right side of
5.0 mm without mandibular advancement was agreed
upon. Two months later, transverse sliding genioplasty
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Y.J. Chen, T.H. Huang, C.Y. Peng, et al.
Figure 4. Pre-surgical evaluation. (A) The mentalis muscle is still in hypertension. (B) Finished stage, with
good interdigitation.
with wire fixation was performed with the patient
under general anesthesia (Figure 6). One month after
this, wrap-around retainers were applied to both dental
arches following removal of the pre-adjusted edgewise appliances.
Treatment results
Figure 5. Frontal view of the patient with
a bite stick in place to show the canting of
the occlusal plane.
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Facial photographs (Figure 7A) show significant
improvement in the facial profile and few class III
facial characteristics. Although there was still mild
facial and dental asymmetry, the patient is now
pleased with his dental and facial appearance.
After active treatment, his upper lip was
coincident with the E line, and the lower lip was 2.0
mm anterior to the E line. The following treatment
goals set in the pretreatment planning were attained,
and the malocclusion was compromisingly treated: (1)
achieving solid intercuspation of the teeth with Class I
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Transverse genioplasty for facial profile improvement
Figure 6. Transverse genioplasty with a 5-mm shift to
the right side.
molar and normal incisor relationships; (2) improving
the lateral crossbite; (3) decreasing the maxillary and
mandibular dental midline deviations; and (4)
achieving an acceptable facial profile (Figure 7). The
distance from the chin button to the facial midline was
reduced from 5 to 2 mm.
The occlusion was reduced to a class I molar
relationship and a Class I cuspid relationship
occlusion with a normal overjet and overbite. The
composite cephalometric tracings superimposed on
the S-N line at sella illustrate the treatment changes
(Figure 3B). The mandibular incisors remained in the
same approximate position with an IMPA angle of 99°.
The FMA angle increased (32°), which increased the
facial height but also helped to ameliorate the Class III
appearance, and the SNB angle decreased to 83°. A
posttreatment panoramic radiograph confirmed that
no pathosis or root resorption had occurred (Figure
7C). There were neither signs nor symptoms of
temporomandibular disorders (TMDs) during the
treatment or retention periods. The patient was given
maxillary and mandibular wrap-around retainers. The
treatment time was 28 months. The right mandibular
first molar was then restored for better long-term
stability (Figure 8).
DISCUSSION
The secret to facial beauty is balanced
proportions of all facial features19,20. The appearance
J Dent Sci 2008‧Vol 3‧No 1
of any face is a composite of all of the anatomic
elements—teeth, bone, and soft tissues—and their
relationships to one another21. The chin is a prominent
facial feature, which plays an important role in the
overall facial appearance22. The position of the chin is
important in establishing correct facial proportions.
The chin gives the appearance of strength to the face13.
A “crooked chin” is the most difficult chin deformity
to properly assess and correct (Figure 1A). This
deformity generally results from a truly 3-dimensional
skeletal abnormality20. Because patients’ views of
themselves are usually in a mirror, discrepancies of
the chin's projection are often not even recognized by
the patient. For these reasons, surgical correction of
minor deformities of the chin is infrequently requested13,20. In contrast, asymmetrical chin deformities
are easily detected by patients, and corrections are
often asked for.
Mandibular asymmetries may be related not
only to asymmetrical positioning, but also to an
asymmetrical morphology of the mandible23.
Differences in the length of the body of the mandible,
as well as differences in the height of the developing
ramus, can lead to asymmetries. The developing
asymmetries may begin early in fetal life24 but may
also be the result of disturbances in postnatal
development, including trauma to the mandibular
condyle25. Condylar hypoplasia may also result in
skeletal asymmetry in which the mandible deviates
toward the affected side26. Compensatory maxillary
asymmetry and canting of the occlusal plane may be
associated with such skeletal asymmetries (Figure 5).
A significantly asymmetrical condylar height can
also be detected with a radiographic examination
(Figure 1D).
Management of axial inclination asymmetries
depends on the treatment plan. Patients who do not
undergo extraction may require maintenance of
asymmetrical compensatory axial inclinations,
although a more-ideal symmetry can be achieved in
patients willing to undergo surgical and extraction
procedures27. Malocclusion in a young adult who
presents with a Class I occlusion on 1 side and a Class
III occlusion on the other side can be of both skeletal
and dental origins. Asymmetrical mechanics can be
used to correct a Class III malocclusion with a midline deviation26. An anterior crisscross elastic can
effectively decrease the dental midline deviation, but
may produce the undesirable side effect of canting the
occlusal plane27. The use of a combination of Class II
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Y.J. Chen, T.H. Huang, C.Y. Peng, et al.
Figure 7. Patient after treatment, showing dramatic improvement in the lower facial profile and an
elegant appearance from genioplasty (A~D). Frontal cephalogram showing the extent of the
underlying skeletal asymmetry (E).
and III elastics can produce rotation of the entire arch.
One side effect of interarch elastics, molar extrusions,
can be minimized by an upper arch wire with a curve
of Spee and a lower arch wire with a reverse curve of
Spee. In addition, tipping back the right mandibular
molars greatly helped decrease the dental midline
deviation and crossbite correction in this case
114
(Figure 3D). Finally, in order to obtain a better
surgical evaluation, the transverse genioplasty was
postponed until the final stage (Figure 4).
In the present case, the prepubertal traumatic
history of the chin may have been the reason for the
mandibular asymmetry, which caused condylar growth
arrest on the left side and mandibular hyperplasia on
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Transverse genioplasty for facial profile improvement
Figure 8. Right mandibular first molar after being restored.
the right. Although a non-extraction treatment
involving compensatory dental changes was selected,
a minor skeletal correction by transverse genioplasty
was performed to reduce the jaw deformity.
Transverse genioplasty without advancement (Figure 7D), which downsizes the surgical risks compared
to other osteotomies for mandibular deformities, is
seldom considered as a simultaneous adjunct to
orthodontic treatment. This case, however, illustrates
the benefits that it can contribute to the final outcome.
The patient’s esthetic appearance was dramatically
enhanced by genioplasty, combined with marked
improvement in the harmonious profile of the lower
third of the face and the chin-neck contour, owing to
relief of the muscle tone by transverse genioplasty
(Figure 7A).
Genioplasty is chin surgery. The chin is a
prominence of the mandible and overlying tissues.
Two notable muscles on the chin are the genioglossus
and mentalis. The genioglossus is behind the chin
under the tongue. It is the muscle that pulls the tongue
forward when you breathe, swallow, and stick out
your tongue. The mentalis is on the front of the chin.
It pushes the lip up, and when used, produces a
puckered appearance28 (Figure 1A). Continued hyperfunction of this muscle may have played a role in
creating this deformity. Surgeons have been using
botulinum toxin A with good success to manage
hyperfunctional facial lines28,29. The paralytic effect,
however, lasts only 3~6 months, although some
investigators have reported a longer duration in
patients exposed over a prolonged period of time29.
Therefore, relaxing the mentalis muscle may have
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resulted in anterosuperior rotation of the genial
segment30, which presents a more-satisfying profile
(Figures 3B, 7A). Aesthetic surgery of the chin is an
extremely useful procedure, which can aid in
achieving balanced proportions of the facial features.
Although augmentation of the chin using alloplasts
can camouflage an anteroposterior chin deficiency,
this technique is not effective in correcting vertical or
transverse deformities of the lower face and chin31.
Therefore, transverse sliding genioplasty was a better
choice for a surgical procedure in this case.
Only by critical clinical, lateral cephalometric,
and P-A cephalometric radiographic analyses (Figure 7E) with soft-tissue markers can these various
aspects be totally appreciated and accordingly
appraised32,33. In a case like the present one, when
correcting a rather gross developmental facial
deformity, improvement can be achieved by lessexacting surgery, and patient satisfaction is frequently
good. However, when dealing with a more-subtle
esthetic variety of deformity, such as an isolated
crooked chin, the patient is generally seeking and only
satisfied with subtle, precise change1,20.
Facial appearances tend to influence the
impressions of those we meet, and our social
interactions are heavily dependent on how we look to
others34-36. Accordingly, the treatment plan should be
closely congruent with and responsive to the patient's
wants, needs, and preferences, and it should also
consider the psychological, social, cultural, and
economic dimensions of the patient in addition to
physical findings18. After all, patient-centered outcomes can never be overemphasized.
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Y.J. Chen, T.H. Huang, C.Y. Peng, et al.
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