Functional genioplasty in growing patients

Original Article
Functional genioplasty in growing patients
Sylvain Chamberlanda; William R. Proffitb; Pier-Eric Chamberlandc
ABSTRACT
Objective: To evaluate the role of age as a moderator of bone regeneration patterns and
symphysis remodeling after genioplasty.
Method: Fifty-four patients who underwent genioplasty at the end of their orthodontic treatment
were divided into three age groups: younger than 15 years at the time of surgery (group 1), 15 to
19 years (group 2), and 20 years or older (group 3). Twenty-three patients who did not accept
genioplasty and had a follow-up radiograph 2 years after the end of their orthodontic treatment
were used as a control group. Patients were evaluated at three time points: immediate preoperative
(T1), immediate postoperative (T2,) and 2 years postsurgery (T3).
Results: The mean genial advancement at surgery was similar for the three age groups, but the
extent of remodeling around the repositioned chin was greater in group 1, less in group 2, and still
less in group 3. Symphysis thickness increased significantly during the 2-year postsurgery interval
for the three groups, and this increase was significantly greater in group 1 than in group 3.
Remodeling above and behind the repositioned chin also was greater in the younger patients. This
was related to greater vertical growth of the dentoalveolar process in the younger patients. There
was no evidence of a deleterious effect on mandibular growth.
Conclusion: The outcomes of forward-upward genioplasty include increased symphysis
thickness, bone apposition above B point, and remodeling at the inferior border. When indications
for this type of genioplasty are recognized, early surgical correction (before age 15) produces a
better outcome in terms of bone remodeling. (Angle Orthod. 0000;00:000–000.)
KEY WORDS: Genioplasty; Inferior border osteotomy; Lip function; Facial proportions
INTRODUCTION
Inferior border osteotomy of the mandible for chin
augmentation was first reported by Trauner and
Obwegeser1 in 1957 and has become widely used as
an isolated procedure or in combination with other
maxillo-mandibular osteotomies. Although the chin can
be repositioned in any direction with this procedure,
simultaneous advancement and upward movement to
correct both a horizontal deficiency and vertical excess
is the most common. Precious and Delaire2 defined
forward-upward repositioning of the chin as a ‘‘func-tional
genioplasty’’ because it provides a beneficial
change in lip function and helps to obtain lip compe-tency
at repose.2 It also tends to reduce lip pressure
against the lower incisors.3 When orthodontic treatment
has created mandibular incisor protrusion, improving
the relationship between the chin and mandibular
incisors (the Holdaway ratio in cephalometric analysis)
is thought to improve the chance of incisor stability—
and one way to do that is to advance the chin rather than
retracting the incisors. This can be particularly helpful
when the improvement in occlusion in Class II patients
was achieved largely by tooth movement because of
minimal or unfavorable mandibular growth.
These functional and stability benefits stand, of
course, in addition to the esthetic improvement
enjoyed with genioplasty. Facial appearance can be
a serious psychosocial handicap, even early in life,4
and functional genioplasty offers a means to improve
esthetics, function, and stability in conjunction with
orthodontic treatment.
Although a number of publications on inferior body
osteotomy for genioplasty have appeared, only a few
a Private practice, Quebec, Canada.
b Kenan Distinguished Professor, Department of Orthodontics,
School of Dentistry, University of North Carolina, Chapel Hill, NC.
c PhD student, Department of Psychology, Universite´ du
Que´bec a` Trois-Rivie` res, Trois-Rivie` res, Quebec, Canada.
Corresponding author: Dr Sylvain Chamberland, 10345 Boul
de l’Ormiere Quebec, Qc G2B 3L2, Canada
(e-mail: drsylchamberland@videotron.ca)
Accepted: June 2014. Submitted: March 2014.
Published Online: July 31, 2014
G 0000 by The EH Angle Education and Research Foundation,
Inc.
DOI: 10.2319/030414-152.1 1 Angle Orthodontist, Vol 00, No 0, 0000

2 CHAMBERLAND, PROFFIT, CHAMBERLAND
studies have data for this procedure in adolescents,
and none include follow-up of a control group who
were evaluated as potentially benefiting from func-tional
genioplasty but rejected it. The optimum age
for genioplasty has been somewhat controversial. The
positive psychosocial reaction to improved facial
appearance would suggest earlier treatment for
severely affected patients4,5; concerns about possible
negative effects on growth and decreased stability
would be the major reason for waiting until little or no
growth remained.6 Martinez et al.7 reported in 1999
that there is better regeneration of symphysis thick-ness
in patients younger than age 15 than in older
nongrowing individuals. More recently, Frapier et al.8,9
suggested that early genioplasty could improve the
direction of mandibular growth and might increase
nasal breathing because of improved lip function, but
these assertions were based on samples that were too
small and diverse for broad generalization.
An isolated lower border osteotomy requires general
anesthesia, but not overnight hospitalization, and is
commonly done as a day-op procedure either in a
hospital or a free-standing surgical center. In the United
States, genioplasty is usually part of a larger orthog-nathic
surgery plan because medical insurance will
almost never cover the cost of an isolated procedure.
This is not the case in Canada, where medical coverage
is provided. The aims of the study were to clarify the
optimal time for functional genioplasty from evaluation
of (1) the pattern of bone remodeling at the chin after
functional genioplasty and (2) the pattern of postsurgical
stability in growing and nongrowing patients.
MATERIALS AND METHODS
Patient Sample
All participants in this research project were treated in
the private orthodontic practice of the senior author. The
surgery patients had lateral cephalometric radiographs
at three time points: T1, immediately prior to genioplasty,
which was done at the end of their orthodontic treatment;
T2, immediately after the genioplasty; and T3, at 2-year
follow-up. The initial sample was all of the 59 patients
who had this surgery between June 1992 and December
2012; five were excluded because of missing radio-graphs,
for a final sample size of 54. This group was
divided into three age groups: younger than 15 years at
time of surgery (group 1, n 5 28), 15 to 19 years (group
2, n 5 16), and 19 years or older (group 3, n 5 10;
Table 1). Skeletal age (maturation of vertebrae) was not
used because chronologic age is more likely to predict
the peak of adolescent growth,10 and age 15 was the
cutoff point in the only previous report of age-related
changes in symphysis remodeling after genioplasty.7
It is difficult to assess exactly how many patients
were offered a genioplasty and declined it, but we were
able to find 23 patients who did not accept genioplasty
and had a follow-up radiograph 2 years after the end of
their orthodontic treatment. This control group (group
4) had only two observation time points: at the end of
orthodontic treatment and 2-year follow-up. They were
similar to the younger surgical patients (group 1) in
age, percentage female, a-p and vertical chin position,
and symphysis thickness at baseline and therefore are
comparable to that group. Five of the control group
eventually joined the surgery group because they
decided to accept genioplasty after their 2-year
postorthodontics records had been obtained.
Surgical Procedure
A mandibular lower border osteotomy was per-formed
with the patient under general anesthesia at
Hoˆ pital l’Enfant-Je´ sus, Que´bec, Canada, by the same
oral-maxillofacial surgeon, following the technique
described by Precious and coworkers.11 Anterior and
superior repositioning of the chin was achieved by
sliding the chin to its new position. For 49 of the 54
patients, wire osteosynthesis was achieved with at
least three transosseous double strands of 28-gauge
stainless-steel wire. The other five patients had bone
screws. Neither the wire nor screw fixation was
removed.
Cephalometric Data
Lateral cephalometric radiographs for patients partic-ipating
in this study prior to mid-2008 were taken on an
Orthophos Ceph machine (Siemens, Beinsheim, Ger-many);
afterward, an OP100 (Instrumentarium, Tuusula,
Finland) unit was used. All radiographs were traced by
Table 1. Patient Characteristics
Baseline Age at T1 (Years) /1-APg (u) ADH (mm) FMA (u)
Group N Mean SD Range % Female Mean SD Range Mean SD Range Mean SD
Group 1 (,15 years) 28 14.00 0.67 12.62 to14.95 32 3.01 1.49 0.4 to 5.3 44.88 2.67 37.1 to 50.7 34.06 4.14
Group 2 (15–19 years) 16 16.65 1.05 16.16 to18.61 44 3.67 1.74 21.2 to 6.5 45.92 3.27 40.1 to 51.1 32.46 3.39
Group 3 (.19 years) 10 28.65 4.96 22.35 to 36.16 40 2.73 1.90 20.3 to 5.6 48.00 4.76 36.9 to 53.1 34.74 6.35
Group 4 (control) 23 14.31 1.41 11.46 to 16.44 39 3.18 1.56 1.0 to 5.8 43.90 2.39 39.5 to 49.6 31.97 4.25
Angle Orthodontist, Vol 00, No 0, 0000

FUNCTIONAL GENIOPLASTY IN GROWING PATIENTS 3
Figure 1. Cephalometric landmarks and dimensional measurements. Symphysis thickness was evaluated by measurement of the distance
between the anterior and posterior borders 4 mm below the apex of the lower incisors (ACP-PCP). Vertical chin height was evaluated by the
perpendicular distance from the mandibular plane to the lower incisor tip (ADH). Remodeling of the area above the repositioned chin was
evaluated by change at B point and symphysis thickness increase; remodeling of the area on the inferior border was evaluated by the change of
the depth of the notch at the posterior limit of the osteotomy cut, by measuring the perpendicular distance from PGP to the mandibular plane (MP).

Figure 2. Facial changes before and after functional genioplasty for a typical patient. Note the improvement in facial proportions, improved lip
closure at repose, and improved display of the incisors on smile. Moving the chin up also moves the lower lip upward and decreases the display
of lower incisors.
the senior author with Quick Ceph Studio (Quick Ceph
Systems, San Diego, Calif). Magnification was calibrated
for both the older scanned films and newer digital
radiographs. An x–y cranial base coordinate system
was constructed through sella with the x-axis drawn 7u to
the sella-nasion line and the y-axis passing through sella,
perpendicular to the x-axis (Figure 1).
For all subjects, the recommendation for genioplasty
was based on clinical evaluation of the prominence and
vertical position of the soft tissue chin relative to the lips
and midface. Cephalometric data for pretreatment a-p
chin deficiency relative to the lower incisors, the vertical
distance from the incisors to the bottom of the chin, and
the mandibular plane angle are shown in Table 1. To
Table 2. Change at Surgery (mm)
Genial Advancement at
Surgery T1–T2 Genial Vertical Reduction T1–T2 /1-APg Change T1–T2
Group n Mean SD Range Mean SD Range Mean SD Range
Group 1 (,15 years) 28 6.45 2.2 2.6 to 10.6 2.93 2.5 22.1 to 7.4 21.61 1.08 22.9 to 2.6
Group 2 (15–19 years) 16 5.88 1.77 1.5 to 9.2 3.53 2.77 20.5 to 8.2 22.04 0.70 23.1 to 20.4
Group 3 (.19 years) 10 5.25 2.79 1.4 to 10.7 3.83 1.88 0 to 7.3 21.64 0.85 22.8 to 20.5

Table 3. Symphysis Thickness at Each Time Point (mm)
T1 T2 T3 T2–T3 T1–T3
n Mean SD Mean SD Mean SD Mean SD Mean SD
Group 1 (,15 years) 28 8.39 1.62 8.50 1.57 11.73 2.86 3.24 2.68 3.44 2.51
Group 2 (15–19 years) 16 8.14 1.78 8.29 1.84 10.35 2.58 2.06 1.24 2.15 1.88
Group 3 (.19 years) 9 8.13 2.37 8.07 2.48 9.18 2.21 1.11 1.02 1.04 1.16
Group 4 (controls) 23 — — 8.84 2.20 8.46 2.25 20.44 0.67 — —
evaluate postsurgical changes in the chin, the focus was
on four measurements (Figure 1): symphysis thickness,
vertical height of the chin relative to the lower incisors,
and remodeling above and behind the chin.
Statistical Analysis
The distribution of the sample was evaluated and
judged to be close enough to normal to use mean,
standard deviation, and range as descriptive statistics.
The study design involved comparison among the three
age groups who underwent genioplasty (groups 1, 2,
and 3) and comparison of the youngest group (group 1)
to an age-matched control group (group 4) with the
same characteristics. For both comparisons, changes
scores between time points were analyzed with multi-variate
analysis of covariance, in which gender effect
was evaluated as a covariate. Although gender did not
contribute to the differences, we kept this effect in the
model to adjust the conclusions for gender. One-sample
t-tests were used to evaluate the chance that data for
each time point were different from zero; pairwise
comparisons with Bonferroni adjustments for multiple
comparisons were used to evaluate the change between
groups. Unlike the Tukey adjustment, the Bonferroni
method does not need correction because of the
unbalanced sample size between groups. The level of
significance was set at P , .05. All of these analyses
were conducted with IBM SPSS Statistics (version 21).
To assess the method error, 15 cephalograms were
redigitized. An analysis of variance showed that there
was no significant difference between the first tracing
and the redigitized tracing. The coefficient of fidelity for
all variables was .9997. The coefficient of fidelity for
the symphysis thickness change and remodeling of the
inferior border (PGP) was .9231. The analysis of the
method error was conducted with SAS 9.4 (SAS
Institute Inc, Chicago, Ill).
RESULTS
Change at Surgery (T1–T2)
Changes at surgery for a typical functional genio-plasty
patient are shown in Figure 2, and the data are
summarized in Table 2. There were no significant
differences in genial advancement or vertical reduction
between the three age groups (Table 2). The changes
were highly statistically significant (,.0001 for both).
Change from Surgery to Follow-up (T2–T3)
Changes in symphysis thickness. Symphysis thick-ness
increased significantly for all three surgical
groups and showed a small but significant decrease
for the controls (Table 3; Figure 3). Pairwise compar-isons
between groups 1 and 3, controlling for different
sample size, showed a significant difference (P 5
.004) between these two groups for the symphysis
thickness change.
When there is considerable variability in treatment
outcomes, as there often is, the percentage of patients
with clinically significant change can provide a better
understanding of the data.12,13 Figure 3 shows that
39% of the youngest patients (group 1) had a 2- to 4-
mm increase in symphysis thickness during the 2 years
postsurgery, and 28% had a .4-mm increase.
Therefore, two-thirds of the youngest patients had a
more than 2-mm increase in symphysis thickness. The
percentage with change .2 mm was smaller in group
2, but two of those patients (7%) had a .4-mm
Figure 3. The percentages of patients with .2- and .4-mm changes
in symphysis thickness after genioplasty. Note the differences in the
genioplasty age groups and the contrast to the control patients.

increase. No patients in the oldest group (group 3) had
a .4-mm change, and only two (20%) had a .2-mm
change. In contrast to the genioplasty groups, no
patient in the control group had an increase in
symphysis thickness from the end of treatment to 2-
year recall, and seven (30%) had a 1-mm or greater
decrease.
Changes in coordinate positions and dimensional
relationships. Data for changes in coordinate positions
for points B, Pg and Me are displayed in Tables 4 and
5, and the changes for Pg and Me are shown
graphically in Figures 4 and 5. It is important to keep
in mind that these changes are due to a combination of
mandibular growth and surface remodeling at and near
the chin.
Horizontal growth change at Pg after genioplasty
(T2–T3) of group 1 was less than the control group, but
the difference was not statistically significant. Group 1
showed a significant forward growth change, while for
groups 2 and 3, the horizontal change at Pg was not
significant (Figure 4). Vertical growth change at Me
after surgery was similar to the control group, and the
vertical change was significant for group 1, group 2, and
controls (Figure 5). Figure 6 shows the pattern of
vertical dentoalveolar change postgenioplasty. All
changes were statistically significant from zero for each
group, but for group 1, the T2–T3 change was
significantly different from groups 2, 3, and 4. One
should keep in mind that this vertical change at Me was
balanced by posterior facial growth: the mandibular
plane angle change for group 1 was not significant.
Pairwise comparisons are shown in Table 6. This
confirms that remodeling in group 1 is different from
remodeling in groups 3 and 4.
Three variables were significantly correlated to the
postsurgical change in symphysis thickness: the
amount of genial advancement, the amount of vertical
dentoalveolar growth, and the age at surgery. The
R value of these three variables taken together was
.47 (r 2 5 .22), and their influence was significant at the
Table 4. Horizontal Changes in Coordinate Position
Group n
T2–T3 (Postsurgery to 2 Years) T1–T3 (Presurgery to 2 Years)
Mean SD
Intragroup
Significance Mean SD
Intragroup
Significance
Horizontal change
D B point Group 1 (,15 years) 28 3.72 2.89 ,.001 4.21 3.47 ,.001
Group 2 (15–19 years) 16 2.13 1.92 ,.001 2.33 1.65 ,.001
Group 3 (.19 years) 9 1.90 1.42 .004 1.68 1.74 .020
Group 4 (controls) 23 2.47 2.57 ,.001 2.47 2.57 ,.001
D BPg to MP Group 1 (,15 years) 28 1.06 1.33 ,.001 21.35 1.39 ,.001
Group 2 (15–19 years) 16 0.85 1.14 .009 21.59 2.40 .018
Group 3 (.19 years) 9 0.69 1.00 n.s. 20.78 1.70 n.s.
Group 4 (controls) 23 20.36 0.58 .007 20.36 0.58 .007
D Pg Group 1 (,15 years) 28 1.17 2.89 .042 7.57 3.90 ,.001
Group 2 (15–19 years) 16 20.21 1.42 n.s. 6.13 1.99 ,.001
Group 3 (.19 years) 9 0.48 2.06 n.s. 5.70 2.75 , .001
Group 4 (controls) 23 2.67 2.85 .005 2.67 2.85 .005
D Symphysis thickness Group 1 (,15 years) 28 3.24 2.68 ,.001 3.44 2.51 ,.001
Group 2 (15–19 years) 16 2.06 1.24 ,.001 2.15 1.88 ,.001
Group 3 (.19 years) 9 1.11 1.02 .011 1.04 1.16 .027
Group 4 (controls) 23 20.44 0.67 .004 20.44 0.67 .004
D Me Group 1 (,15 years) 28 0.78 2.78 n.s. 7.68 3.81 ,.001
Group 2 (15–19 years) 16 0.00 1.71 n.s. 6.79 2.27 ,.001
Group 3 (.19 years) 9 0.68 1.69 n.s. 6.42 3.38 ,.001
Group 4 (controls) 23 2.38 2.82 ,.001 2.38 2.82 ,.001
D Pg relative to N
perpendicular to FH
Group 1 (,15 years) 28 20.48 2.54 n.s. 5.60 3.31 ,.001
Group 2 (15–19 years) 16 20.86 1.25 .015 5.32 1.70 ,.001
Group 3 (.19 years) 9 20.24 2.25 n.s. 4.93 3.14 .002
Group 4 (controls) 23 0.77 2.07 n.s. 0.77 2.07 n.s.
Sagittal relationship
D ABOP occlusal
relationship
Group 1 (,15 years) 28 20.69 1.57 .028 21.31 1.75 ,.001
Group 2 (15–19 years) 19 21.44 2.09 .015 21.19 1.47 .005
Group 3 (.19 years) 9 21.17 1.46 .043 21.79 1.67 .012
D/1-APg Group 1 (,15 years) 28 0.80 0.85 ,.001 20.87 1.01 ,.001
Group 2 (15–19 years) 16 20.03 0.73 n.s. 22.18 0.53 ,.001
Group 3 (.19 years) 9 0.38 0.65 n.s. 21.39 0.69 ,.001
Group 4 (controls) 23 0.43 0.91 .033 0.43 0.91 .033

P , .05 level (P 5 .03). When the predictor variables
were ranked by the standardized coefficient beta, the
result clearly showed that the younger the age at
surgery and the greater the dentoalveolar growth as
incisors erupted, the more the symphysis would
increase in thickness due to bone apposition. The
amount of genial advancement was not a determinant.
Remodeling changes. Remodeling of the symphysis
after genioplasty involves bone apposition above the
repositioned chin, with changes leading up to and even
beyond point B, and removal of bone adjacent to the
notch in the lower border of the mandible that is
present after the chin has been moved (Figures 7 and
8). Figure 8 illustrates the typical pattern of remodeling
in the younger patients. Statistical analysis showed
that the decrease in the depth of the notch at the
inferior border was significant for groups 1 and 2, but
no significant change was noted for the adult group
(Figure 7; Table 5). There was no significant change of
the inferior border in the control group.
Ranking the predictor variables confirmed that the
greater the dentoalveolar growth postsurgery, the
more complete the remodeling in both areas, but
neither the amount of genial advancement nor the age
at surgery were significant predictors. It is clear,
therefore, that age at genioplasty, which affects the
amount of incisor eruption afterward, does make a
difference in the extent of both bone apposition and
remodeling, with more apposition and remodeling in
patients younger than 15 years, less in late adoles-cents,
and still less in adults.
Stability of the Surgical Repositioning
It is important to keep in mind that postsurgical
changes in the position of the chin were due to a
combination of mandibular growth and surface remode-ling
at and near the chin. For the younger patients, this
is best evaluated by comparing the change in group 1
with the control group. The mean A-P change at Pg after
genioplasty (T2–T3) of group 1 was less than the control
group (ie, the genioplasty patients were slightly more
stable), but the difference was small and not statistically
significant (see Figure 4). The vertical change at Me
after surgery also was similar to the control group (see
Figure 5).
The data show, therefore, that forward and down-ward
growth at the chin in this sample was not
significantly affected by genioplasty and that the
changes in chin position produced by the genioplasty
were maintained in growing patients.
DISCUSSION
The data from this study make it clear that both the
amount of new bone formation after genioplasty and
the extent of remodeling around the repositioned chin
Table 5. Vertical Changes in Coordinate Position
T2–T3 (Postsurgery to 2 Years) T1–T3 (Presurgery to 2 Years)
Group n Mean SD
Intragroup
Significance Mean SD
Intragroup
Significance
Vertical change
D B point Group 1 (,15 years) 28 21.75 2.49 .001 21.93 2.73 .001
Group 2 (15–19 years) 16 20.53 3.70 n.s. 20.67 3.50 n.s.
Group 3 (.19 years) 9 20.09 2.90 n.s. 20.02 2.47 n.s.
Group 4 (controls) 23 22.89 3.65 .001 22.89 3.65 .001
D Pg Group 1 (,15 years) 28 24.10 3.36 ,.001 21.75 3.59 .016
Group 2 (15–19 years) 16 22.71 2.32 ,.001 0.01 2.69 n.s.
Group 3 (.19 years) 9 21.04 2.52 n.s. 1.86 3.12 n.s.
Group 4 (controls) 23 23.69 4.08 ,.001 23.69 4.08 ,.001
D Me Group 1 (,15 years) 28 25.01 3.09 ,.001 22.14 3.30 .002
Group 2 (15–19 years) 16 22.57 2.43 .001 0.90 3.69 n.s.
Group 3 (.19 years) 9 21.26 2.35 n.s. 2.60 2.83 .025
Group 4 (controls) 23 24.46 4.61 ,.001 24.46 4.61 ,.001
D FMA Group 1 (,15 years) 28 0.40 1.61 n.s. 25.89 2.50 ,.001
Group 2 (15–19 years) 16 0.86 0.90 .002 25.48 2.25 ,.001
Group 3 (.19 years) 9 0.39 1.28 n.s. 26.14 2.07 ,.001
Group 4 (controls) 23 20.72 1.62 .044 20.72 1.62 .044
D ADH (anterior dental height) Group 1 (,15 years) 28 3.11 1.93 ,.001 22.78 1.98 ,.001
Group 2 (15–19 years) 16 1.20 1.13 .001 24.86 2.39 ,.001
Group 3 (.19 years) 9 0.74 0.89 .036 25.29 1.92 ,.001
Group 4 (controls) 23 1.84 1.86 ,.001 1.84 1.86 ,.001
D PGP to MP Group 1 (,15 years) 28 1.17 1.29 ,.001 22.84 1.88 ,.001
Group 2 (15–19 years) 16 0.62 0.88 .013 23.26 1.75 ,.001
Group 3 (.19 years) 9 0.30 1.00 n.s. 23.79 1.27 .025

Figure 4. Horizontal change at Pg. The younger genioplasty patients and the controls showed significant forward growth at Pg; the change at Pg
for groups 2 and 3 was nonsignificant. The growth change of group 1 was not statistically different from the controls (ie, there was no evidence of
decreased forward growth in the young genioplasty patients).
are greater in patients who are still in mid-adolescence
than in late adolescents and adults. Our results both
confirm and extend the earlier report by Martinez that
showed better healing in patients younger than age 157
and support other findings6,14–18,21 that after genioplas-ty,
bone remodeling occurs at the inferior border of the
proximal segment between the distal point of the
osteotomy cut and the advanced distal segment. Our
groups 1 and 2 showed a statistically significant mean
reduction of this notch (1.2 6 1.3 mm and 0.6 6
0.9 mm, respectively), while the adult group had a
modest nonsignificant reduction of 0.3 6 1.0 mm.
In this study, the control group had a slight but
significant resorption at B point (0.4 6 0.6 mm), which
is consistent with the usual pattern of growth at the
chin in adolescence. Following genioplasty, as in Park
et al.,18 Shaughnessy et al.,19 and Precious et al.,11,17
we found that bone apposition occurred at B point, with
a similar change in all three age groups (0.7 to
1.0 mm). Bony angles above the repositioned chin
became rounded, and rough edges became smooth.
Shaughnessy et al.19 suggested that the autogenous
bone grafts from the iliac crest that they placed in this
area were responsible for the improved contours.
Since none of the patients of the present study
received a graft and all had significant apposition at
B point, we question the indication for grafting bone
into that area, particularly with bone from a donor site
such as the iliac crest that requires invasive surgery.
Would it have made a difference if we used skeletal
age instead of chronologic age in separating the three
groups? It would have been possible to do that without
additional radiation by using maturation of the cervical
vertebrae. The conclusion of a recent review of
methods to establish peak growth at adolescence,
however, concluded that chronologic age is better.10 It
is possible that the group younger than 15 years had
some relatively mature girls, while the age 15–19
group had some relatively immature males, but that
would have minimized rather than augmented the
differences we observed.
The increased remodeling of the facial alveolar bone
above the osteotomy site is important in the context of
bone support for the lower incisors, because lower
incisors tend to be proclined in individuals with a
deficient chin even without treatment. This often is

Figure 5. Vertical change at Me. Vertical growth change at Me after surgery (T2–T3) was significant for groups 1 and 2 and was similar to the
control group, showing that vertical growth at Me was not affected by genioplasty.

Figure 6. Vertical alveolar dental change. All changes were statistically significant for each group. Note that the mean 6-mm difference between
the young genioplasty patients and controls created by surgery was maintained at 2-year recall.
increased during their orthodontic treatment as the
lower arch is expanded to align crowded incisors and/
or Class II elastics are used to correct the occlusion.
The result can be bone dehiscence and stripping of
gingival tissue. Our data show that as the bone
remodels after genioplasty, there is formation of new
alveolar bone facial to the teeth at a higher level in the
younger patients, and this can be attributed to
postgenioplasty eruption of the teeth as face height
increases more in the younger group.
Our patients also had formation of new bone on
the lingual side behind the prominence of the chin, with
a greater increase in symphysis thickness in the
younger patients that persisted during the first 2 years

posttreatment. The symphysis is a highly stressed
area during normal function. Is greater symphysis
strength a long-term outcome of genioplasty via lower
border osteotomy? We have no data to support that
possibility, but there is nothing to indicate that
genioplasty before the completion of mandibular
growth weakens the chin.
Does repositioning the chin have a deleterious effect
on mandibular growth? That is a valid concern and has
been a major reason for delaying it until growth is
essentially completed. Our control group of mandibular
deficient young patients who did not accept genioplasty
allows a comparison of mandibular growth in treated
and untreated individuals with similar mandibular
morphology. Growth at the chin is largely due to growth
of the mandible, but in the normal growth pattern, the
chin becomes more prominent, not by apposition in the
pogonion area, but by resorption above pogonion that
extends upward toward point B.14 In a growing individual
with an indication for forward-upward genioplasty, data
from our control group show that lip incompetency
persists, facial convexity is maintained, bone resorption
occurs at point B, and symphysis thickness has a
tendency to decrease. Change or the lack of it in a
typical control patient is shown in Figure 9.
Although our data show no evidence to support a
negative effect on mandibular growth from a lower
border osteotomy, whether it is done in early adoles-cence
or later, it will be important to follow the younger
patients until the end of the normal growth period to be
sure that there is no residual effect, and this is
planned. The mandibular plane angle decreases
slightly during normal adolescent growth, and this is
what we observed in both the younger genioplasty
patients and the controls. It can be difficult to avoid
unerupted permanent teeth during a lower border
osteotomy in a child, and this is a contraindication for
early genioplasty. Eruption of mandibular canines,
usually around age 12–13 years, removes that
limitation for most individuals.
Most previous studies of stability after genioplasty
have reported that it is the most stable of the
orthognathic surgery procedures and that significant
relapse is almost never observed.15,19,20 Tulasne,16
using a different surgical procedure than the one in
this study, reported greater relapse (about a 40%
change) for young patients. Martinez et al.7 also noted
greater relapse in their younger group (a 16% change),
but it was neither clinically nor statistically significant.
Our findings do not support a greater relapse at Pg for
younger growing patients. Since almost all of our
patients (91%) had wire fixation, better postsurgical
stability with more costly bone screws may not be a
consideration for this type of genioplasty.17
CONCLUSIONS
N Benefits of genioplasty via a lower border osteotomy
that moves the chin forward and upward (a functional
genioplasty) include increased symphysis thickness,
bone apposition at B point, and remodeling at the
inferior border. Better bone apposition and remodel-ing
is observed in younger patient compared with
adults.
Table 6. Pairwise Comparisons Between Groups
T2–T3 T1–T3
Group
1–Group 4
Group
1–Group 2
Group
1–Group 3
Group
2–Group 3
Group
1–Group 4
Group
1–Group 2
Group
1–Group 3
Group
2–Group 3
Horizontal change
D B point n.s. n.s. .012 n.s. n.s. n.s. n.s. n.s.
D BPg to MP ,.001 n.s. n.s. n.s. .002 n.s. n.s. n.s.
D Pg .069 n.s. n.s. n.s. ,.001 n.s. n.s. n.s.
D Symphysis thickness ,.001 n.s. .004 n.s. ,.001 n.s. .002 n.s.
D Me .049 n.s. n.s. n.s. ,.001 n.s. n.s. n.s.
D Pg relative to N perpendicular to FH n.s. n.s. n.s. n.s. ,.001 n.s. n.s. n.s.
Vertical change
D B point n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s.
D Pg n.s. n.s. .006 n.s. n.s. n.s. .018 n.s.
D Me n.s. .022 .003 n.s. n.s. n.s. .013 n.s.
D FMA .017 n.s. n.s. n.s. ,.001 n.s. n.s. n.s.
D ADH (anterior dental height) .021 ,.001 ,.001 n.s. ,.001 .013 .003 n.s.
D PGP to MP ,.001 n.s. .156 n.s. ,.001 n.s. n.s. n.s.
Sagittal relationship
D ABOP occlusal relationship .028 n.s. n.s. n.s. .001 n.s. n.s. n.s.
D/1-APg n.s. .004 n.s. n.s. ,.001 ,.001 n.s. .012

Figure 7. Remodeling at the inferior border. The notch at the inferior border of the proximal segment between the distal point of the osteotomy cut
and the advanced distal segment was significantly reduced for groups 1 and 2 (1.2 6 1.3 mm and 0.6 6 0.9 mm, respectively), while the adult
group had a modest nonsignificant reduction of 0.3 6 1.0 mm. The net outcome at T3 showed a significant decrease of the depth of this notch
when comparing group 1 to adults (P 5 .018).

Figure 8. The typical pattern of bone remodeling in young patients as seen in superimposed cephalometric tracings. Note that as growth
occurred, remodeling added bone above the repositioned chin segment and decreased the depth of the notch on the inferior border. These
changes are greater in the younger patients.
N When indications for such a genioplasty are recog-nized,
early surgical correction (before age 15)
produces a better outcome in terms of bone remodel-ing.
This is related primarily to greater vertical growth of
the dentoalveolar process in the younger patients.
N There is no difference in postsurgical stability in
younger and older genioplasty patients.
ACKNOWLEDGMENTS
We thank Dr Dany Morais for his surgical excellence, Mr.
Warren McCollum for creating the graphs and charts, Ms
Ramona Hutton-Howe for preparation of photographs for
publication, Mr David Emond of Laval University for statistical
consultation, and the Orthodontic Fund of the Dental Foundation
of North Carolina for support of production costs. The junior
author is supported by a doctoral scholarship from the
Desjardins Foundation, the Quebec Research Fund on Society
and Culture, and Social Sciences and Humanities Research
Council of Canada.
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Figure 9. Facial changes in a typical untreated control patient, who was age 15 years 10 months at the end of orthodontic treatment and age
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