Advancement genioplasty in Class I patients: predictability and stability of facial profile changes

Abstract

This retrospective study evaluated the skeletal and soft tissue facial profile changes as well as the predictability and the short-term stability of the soft-tissue response to advancement genioplasty in Class I dental arch relationship patients. The study included 14 adult patients who presented a Class I dental arch but a Class II skeletal arch relationship and underwent advancement genioplasty exclusively. Lateral cephalograms taken immediately preoperatively (T1), immediately postoperatively (T2) and 1 year postoperatively (T3) were analysed. The hard tissue pogonion was sagittally advanced by an average of 7.9 mm ( p < 0.001) (T1–T2). The soft tissue chin followed the sagittal skeletal chin movement and exceeded chin advancement due to the initial soft tissue swelling. In the vertical dimension, the skeletal chin moved 3.0 mm ( p < 0.01) upwards whilst the soft tissue chin moved only 2.1 mm upwards ( p < 0.01). All profile convexity angles increased significantly ( p < 0.001), implying that the profile was straightened by the advancement of the chin. In the short term, advancement genioplasty was a predictable and stable procedure for chin correction. A ratio of 1:1 may be used to predict the sagittal soft tissue to bony movements for the period from before to 1 year after surgery.

Facial appearance is important for psychological well-being and social acceptance, because the face, as the most distinguished body part, influences the manner of perception by others, thereby modulating social interaction .

P hilipps et al. reported that subjects with Class I profiles achieve higher attractiveness scores from patients, their peers, orthodontists and oral surgeons compared with patients with Class II and III profiles. J ohnston et al. reported that facial profiles with an Eastman normal SNB value of 78 degrees were rated to be the most attractive. H önn et al. confirmed the increased attractiveness of straight, compared with convex, facial profiles. Other studies report that Class II profiles are regarded as less attractive than Class III profiles . Convex Class II profiles seem to be the least attractive.

Many adult patients consult an orthodontist and/or maxillofacial surgeon wanting to improve their facial and dental aesthetics because beauty has great social power and results in more social contacts . The possible effects of orthodontic/surgical treatment on facial aesthetics are amongst the decisive factors for treatment planning.

For adult Class II patients there are basically three possible treatment options: dental camouflage, growth reactivation or orthognathic surgery . Although orthognathic surgery has the greatest potential to improve facial aesthetics, a soft tissue profile convexity <160° (NS-Sn-PgS, Fig. 1 ) and an ANB angle >6° are necessary for profiles to be consistently perceived as improved after surgery and thus, to limit the probability for profile worsening and to justify the risks and costs of a surgical approach. Therefore, especially in borderline adult Class II patients, conservative treatment options (dental camouflage or growth reactivation) must be considered. Smaller skeletal treatment effects have to be expected for adult Class II patients treated with both dentofacial orthopaedics and dental camouflage compared with orthognathic surgery patients . After treatment these patients might still present a convex profile with a deficient chin despite the orthodontically achieved Class I dental arch relationship. A genioplasty offers patient with Class I dental arch relationships the possibility to correct their chin position three-dimensionally and to attain a reduction in facial profile convexity and thus a more attractive profile.

Fig. 1
Hard and soft tissue landmarks and reference lines used in the cephalometric analysis. A: deepest point on contour of maxilla between anterior nasal spine and incisor. E-Line: aesthetic line, line connecting No and PgS. LL: lower lip: Most anterior point of lower lip. ML: mandibular line, line connecting gnathion and the most caudal point of the corpus mandibulae in the region of the jaw angle. N: nasion: most anterior point of frontonasal suture No: most anterior point of the tip of the nose. NL: nasal line, line connecting anterior and posterior nasal spine. Ns: soft tissue nasion. NSL: nasion-sella-line, line connecting nasion and sella point. NS-Sn-PgS: soft tissue profile convexity. Pg: pogonion, most anterior point of bony chin contour. PgS: soft tissue pogonion, most anterior point of soft tissue chin contour. Pm: pterygomaxillare, intersection of shade of the fossa pterygopalatina with posterior nasal spine. S: sella-point, centre of sella turcica. Sn: subnasale: point at which columnella merges with upper lip. Spa: anterior nasal spine, most anterior point of the nasal spine. UL: upper lip, most anterior point of upper lip.

Several studies have dealt with the stability and predictability of advancement genioplasty . Most of these studies analysed patients with a comprehensive orthodontic-othognathic surgery approach, including mono- or bimaxillary jaw surgery. As these procedures also influence the soft tissue profile, it is not possible to assess the specific effects of advancement genioplasty. Only a few studies have investigated genioplasty as a solitary surgical procedure . None of these studies defined the dental arch relationship of the patients exactly, which could influence the facial profile changes. The aim of this study was to assess the stability and predictability of advancement genioplasty in Class I dental arch relationship patients with increased soft tissue profile convexity.

Patients and methods

The patients comprised of 14 adults (11 female, 3 male) with a Class I dental arch relationship with normal overjet and overbite but a Class II jaw base relationship ( Table 1 ) who had undergone an advancement genioplasty exclusively. The patients were selected from the files of the private practice of Dhr. Mulié, Zoetermeer, The Netherlands. The pre-treatment age of the patients was 26.2 ± 8.4 years. The surgical procedure was performed by two oral-maxillofacial surgeons. The surgical intervention to advance the chin consisted of an inferior border osteotomy. The genial segment was stabilized either with interosseus wires (11 patients) or a rigid fixation plate (3 patients).

Table 1
Pre-treatment cephalometric characteristics of 14 genioplasty patients.
Variable Mean SD Range
SNB [°] 71.7 3.8 65.8–78.3
ANB [°] 8.0 2.1 4.0–11.5
SNPg [°] 71.6 3.6 66.8–77.5
NAPg [°] 163.8 4.6 157.3–173.3
ML/NSL [°] 45.1 4.9 36.8–53.3

Lateral cephalograms (LC) in habitual occlusion taken immediately preoperatively (T1), immediately postoperatively (T2) and 1 year postoperatively (T3), were analysed. All radiographs were evaluated by the same examiner (C.E.) on two separate occasions at least 2 weeks apart. The mean of the duplicate registrations was used in the final evaluation.

A standard cephalometric analysis was performed to describe the skeleto-facial morphology as well as the profile changes ( Fig. 1 ). In addition, SO-Analysis was used to analyse sagittal and vertical changes ( Fig. 2 ). Before treatment, the following reference points and lines were defined on the LC: the nasion-sella-line (NSL), the occlusal line (OL) and the occlusal line perpendicular (OLp) through sella (S). The OL and the OLp were used as a reference grid. The OL/OLp reference grid was transferred from the first to the subsequent LC (T2, T3) after superimposition of the radiographs on the NSL at S. The sagittal distances between the variables (A-point, pogonion, soft tissue pogonion, mentolabial fold) and the reference grid were measured parallel to OL. In addition, the vertical distances to OL were assessed.

Fig. 2
Hard and soft tissue landmarks and reference lines used in the SO-Analysis. Mlf: Mentolabial fold, deepest point between soft tissue chin and lower lip. OL: occlusal line, line connecting edge of the most anterior upper incisor and distobuccal cusp of the upper first molar. OLp: occlusal line perpendicular, line perpendicular to OL across sella-point (See Fig. 1 for other abbreviations.).

Statistical analysis

Statistical analysis was carried out using SPSS (Version 15.0) for Windows. Means, standard deviations and ranges were calculated. Normal distribution and homogeneity of variance was ascertained using the Kolmogornov–Smirnov test and the Levene test ( p ≤ 0.05), respectively. Parametric statistics ( T -test for pairwise comparison: p ≤ 0.05) were applied to identify significant changes in cephalometric variables between the different time points. Associations between variables were analysed by calculating Pearson’s correlation coefficients. All statistical analysis was performed at a significance level of 5%.

Statistical analysis

Statistical analysis was carried out using SPSS (Version 15.0) for Windows. Means, standard deviations and ranges were calculated. Normal distribution and homogeneity of variance was ascertained using the Kolmogornov–Smirnov test and the Levene test ( p ≤ 0.05), respectively. Parametric statistics ( T -test for pairwise comparison: p ≤ 0.05) were applied to identify significant changes in cephalometric variables between the different time points. Associations between variables were analysed by calculating Pearson’s correlation coefficients. All statistical analysis was performed at a significance level of 5%.

Results

The mean changes of the various cephalometric landmarks between T1 and T2 as well as during the follow-up period 1 year postoperatively (T2–T3) are shown in Table 2 .

Table 2
Hard and soft tissue cephalometric changes in 14 genioplasty patients during the different observation periods.
Variable T2–T1 T3–T2 T3–T1
Mean SD Range p Mean SD Range p Mean SD Range p
Hard tissue
Sagittal
Pg/OLp [mm] 7.9 2.09 4.50–11.25 0.000 −0.1 0.95 −1.25–1.75 0.836 7.8 2.43 4.50–12.25 0.000
SNPg [°] 3.6 0.93 1.50–5.25 0.000 0.1 1.34 −1.25–4.50 0.845 3.5 1.89 1.50–9.25 0.000
N-A-Pg [°] 6.5 2.09 3.50–9.75 0.000 −0.1 1.16 −2.25–2.50 0.865 6.4 2.40 2.50–10.25 0.000
Vertical
Pg/OL [mm] −3.0 2.92 −9.25–2.50 0.002 1.6 1.25 −0.25–4.75 0.000 −1.4 3.00 −7.00–3.50 0.106
ML/NSL [°] −3.9 2.17 −9.25–(−1.00) 0.000 −0.2 1.01 −3.00–1.25 0.563 −4.1 2.36 −9.50–(−1.50) 0.000
Soft tissue
Sagittal
PgS/OLp [mm] 10.5 2.33 6.25–14.50 0.000 −2.9 2.58 −7.50–0.75 0.001 7.6 1.93 3.50–10.75 0.000
NS-Sn-PgS [°] 8.9 2.20 4.75–12.00 0.000 −2.2 2.21 −7.00–0.50 0.003 6.7 1.68 3.00–8.75 0.000
Mlf/OLp [mm] 5.5 2.85 1.25–9.75 0.000 −2.0 2.98 −6.00–6.25 0.026 3.5 3.76 −1.5–13.25 0.004
Mlf depth [mm] −0.4 1.21 −2.25–1.50 0.245 −0.3 0.69 −1.50–1.25 0.126 −0.7 1.08 −2.50–1.25 0.031
UL-EL [mm] −3.6 1.30 −5.25–(−1.00) 0.000 0.5 0.96 −1.25–2.25 0.057 −3.1 0.10 −4.50–(−1.25) 0.000
LL-EL [mm] −5.0 2.01 −8.25–(−1.25) 0.000 −0.3 1.15 −2.00–2.25 0.291 −5.3 1.47 −8.00–(−3.25) 0.000
Vertical
PgS/OL [mm] −2.1 2.49 −9.75–0.25 0.007 1.6 2.79 −3.75–6.00 0.053 −0.5 3.64 −6.75–4.25 0.591
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Jan 27, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Advancement genioplasty in Class I patients: predictability and stability of facial profile changes
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