Orthodontic camouflage versus orthognathic surgery for class III deformity: comparative cephalometric analysis

Abstract

The objective of this study was to compare different cephalometric variables in adult patients with class III malocclusions before and after treatment, in order to determine which variables are indicative of orthodontic camouflage or orthognathic surgery. The cases of 156 adult patients were assessed: 77 treated with orthodontic camouflage and 79 treated with orthodontics and orthognathic surgery. The following cephalometric variables were measured on pre-treatment (T1) and post-treatment (T2) lateral cephalograms: sella–nasion–A-point (SNA), sella–nasion–B-point (SNB), and A-point–nasion–B-point (ANB) angles, Wits appraisal, facial axis angle, mandibular plane angle, upper and lower incisor inclination, and inter-incisal angle. There were statistically significant differences in cephalometric variables before and after treatment between the two groups. The percentage of normal pre-treatment measurements in the camouflage orthodontics group was 30.7%, which worsened slightly to 28.4% post-treatment. However in the group receiving surgery, this was 24.5% pre-treatment, improving to 33.5% after surgery. SNA, SNB, Wits appraisal, lower incisor inclination, and inter-incisal angle showed differences between the two groups before and after treatment. Wits appraisal, lower incisor inclination, and inter-incisal angle were indicative of one or other treatment. Upper and lower incisor decompensation in both groups did not reach ideal values, which impeded complete skeletal correction in 52% of surgical cases.

The prevalence of class III malocclusion varies considerably between Asians (12%), Europeans (1.5–5.3%), and Caucasians (1–4%). The A-point–nasion–B-point (ANB) angle is one of the most widely used variables for determining skeletal class, although some authors consider that Wits appraisal is the most useful parameter for identifying patients who can then be treated by orthodontic treatment alone or in combination with orthognathic surgery. Wits is the distance in millimetres from A point to B point projected and measured on the occlusal plane.

Dentoalveolar compensation before treatment varies depending on the skeletal discrepancies. Correct positioning of the lower incisors has been considered an important treatment objective before orthognathic surgery. Some authors have stated that certain skeletal class III patients treated with orthognathic surgery showed more severe skeletal discrepancies and greater compensation in incisor inclination before surgery than others.

Non-growing patients with moderate class III skeletal malocclusion and acceptable facial aesthetics can benefit from camouflage orthodontic treatment, while patients with severe class III skeletal malocclusion can benefit from orthognathic surgery. When surgical treatment is planned, an optimal result will depend on incisor decompensation. Some of these patients fail to achieve an ideal ANB angle or an optimal result due to incomplete decompensation of the upper and lower incisors resulting from a lack of vestibular bone support or excessive retroclination of the lower incisors before treatment.

Studies comparing class III patients treated by orthodontics alone or by orthognathic surgery are scarce. The aims of this study were (1) to compare different cephalometric variables in adult patients with class III malocclusion between a group treated with camouflage orthodontics and another treated with orthodontics and orthognathic surgery, in order to determine which variables are indicative of one or other treatment, and (2) to evaluate the repercussions of incisor decompensation on the skeletal correction of surgical cases.

Materials and methods

The protocol for this cross-sectional observational human study was approved by the Ethics Committee on Human Research of the University of Valencia, Spain. Rights were protected by the Institutional Review Board. This study followed criteria established in the Declaration of Helsinki for research involving human subjects, and also conformed to STROBE guidelines.

Power analysis showed that a sample size of at least 60 patients would provide an 80% probability of detecting a medium effect ( f = 0.2) associated with an interaction term, using an analysis of variance (ANOVA) model at a confidence level of 95% and assuming a correlation of 0.45 among repeated measurements.

Three hundred and forty patients who underwent treatment in the Orthodontic Department of the Faculty of Medicine and Dentistry, University of Valencia, Spain, between January 2005 and April 2015 were selected to take part in the study. A number of additional patients were recruited to compensate for possible dropouts.

Inclusion criteria established prior to commencement were the following: age over 20 years at the beginning of treatment, Wits appraisal ≤3 mm, good quality initial and final lateral radiographs, patients who had not undergone any extractions, and patients without any congenital deformity, syndrome, or cleft palate.

Following the application of the inclusion criteria, a sample of 156 patients was selected (mean age 23.2 ± 2.6 years, range 20.5–31.1 years). Seventy-seven had received camouflage orthodontic treatment (group C; 36 female, 41 male), while 79 patients had undergone surgery and formed the surgery group (group S; 30 female, 49 male). Of these latter patients, 30 underwent maxillary advancement, 16 underwent mandibular setback, and 33 underwent bimaxillary surgery.

Initial (T1) and final (T2) lateral cephalograms were selected for the cephalometric study. Fourteen cephalometric hard tissue landmarks per radiograph were digitized and nine measurements were obtained. These measurements were based on the cephalometric analyses of Steiner and Tweed ( Fig. 1 and Table 1 ). The cephalometric analysis software used was NemoCeph 11.3.1 (Nemotec, Madrid, Spain).

Dec 14, 2017 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Orthodontic camouflage versus orthognathic surgery for class III deformity: comparative cephalometric analysis
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