Brienne Roloff DDS; Greg Huang DMD, MSD, MPH
Surgical correction of skeletal Class III malocclusion after combined maxillary and mandibular procedures appears to be stable for maxillary advancements up to 5 mm and for the correction of presurgical sagittal intermaxillary discrepancies smaller than 7 mm.
Studies with large sample sizes and patient-oriented outcomes are needed to properly evaluate the effectiveness and stability factors in bimaxillary surgery of Class III malocclusions.
1) Is bimaxillary surgery of skeletal Class III malocclusion effective? 2) Are there any factors that influence stability/relapse following bimaxillary surgery of skeletal Class III malocclusion?
The authors searched Medline until October 2007 using MeSH. They also manually and electronically searched the Cochrane Controlled Clinical Trials Register. The inclusion criteria included: a) systematic reviews, meta-analysis, RCCTs, CCTs, prospective and retrospective studies with and without controls, and clinical trials comparing at least 2 surgical strategies without a control group; b) articles written in English; c) permanent dentition and adult patients with skeletal Class III malocclusion; d) lateral cephalometric radiographs taken in natural head position; e) bimaxillary surgery; and f) follow-up of at least 12 months after surgery. The outcomes assessed were dental and skeletal measurements, such as overjet and ANB angle.
The search strategy yielded 1783 articles. Fifteen articles qualified for final review after inclusion/exclusion criteria were applied. Quality was judged as low in 2 studies, as medium in 12 studies, and as medium/high in 1 study. Seven articles showed correction of the sagittal intermaxillary relationships and overjet after surgery, as well as at the latest follow-up. Two studies declared the success rates to be 80% and greater. Analysis of the 15 studies revealed the following trends for the maxilla: the horizontal stability of surgical outcomes in the maxilla might be negatively influenced by surgical advancement greater than 6 mm and by the use of semirigid fixation or resorbable plates and screws to stabilize when the advancement was greater than 5 mm; double jaw surgery improved vertical stability of the maxilla when it was to be moved down at surgery. Factors of mandibular relapse were: the degree of intraoperative clockwise rotation of the mandibular proximal segment, the amount of mandibular setback, excessive posterior condylar displacement in the glenoid cavity, and altered orientation and stretching of the pterygomasseteric sling.
Surgical correction of skeletal Class III malocclusion after combined maxillary and mandibular procedures appears to be fairly stable, independent of the type of fixation used to stabilize the mandible, for maxillary advancements up to 5-6 mm (especially with superior repositioning) and for the correction of presurgical sagittal intermaxillary discrepancies smaller than 7 mm. A limited degree of intraoperative clockwise rotation of the mandibular proximal segment along with limited “stretching” of the muscles are additional factors of post-surgical stability.
Source of Funding:
The source of funding was not reported.
Importance and Context:
It has been estimated that one-fourth of Class III patients may need surgery at the completion of active growth for the correction of the dentoskeletal disharmony, as they may not have responded satisfactorily to orthopedic therapy1,2. Thus, it is important to understand the effectiveness, stability, and limitations of surgical correction, which was the focus of this review.
Strengths and Weaknesses of the Systematic Review:
The search method of this systematic review could have been improved. Only 1 database was formally searched. Although the authors stated they performed both a manual and electronic search of the Cochrane database, they did not provide search dates or methodology details. Also, they only included English-only articles. The authors also stated their inclusion criteria, but they did not provide a list of the excluded literature. Strengths of the review were: 2 independent reviewers separately assessed the articles; the articles were blinded to the authors who performed the data extraction and analysis; study characteristics were provided; a quality assessment was performed. However, several criteria for judging study quality were intended for RCTs, but only 1 of the studies was an RCT. The authors did not explain how the final quality rating was determined. Also, the authors did not synthesize data in the form of a meta-analysis, which would have strengthened their conclusions. Therefore, their conclusions are qualitative, and difficult to follow from the long tables that are presented.
Strengths and Weaknesses of the Evidence:
The review identified only 1 RCT, which could not be classified as high quality because of its design and reporting problems. The majority of the studies were retrospective, longitudinal reports, and did not report previous estimates of sample size, withdrawals, and blinding in measurements. The treatment strategies employed were heterogeneous, which may have made meta-analysis challenging. Many studies report a follow-up time of 12 months. This may be inadequate to assess stability if follow-up means 12 months after surgery instead of 12 months after completion of orthodontic treatment.
Implications for Dental Practice:
The limited evidence indicates that bimaxillary surgery for the correction Class III malocclusion is an effective procedure, with success rates of 80% or greater reported in 2 studies. Surgical correction appears to be stable for maxillary advancements up to 5 mm and for the correction of presurgical sagittal intermaxillary discrepancies smaller than 7 mm. However, the evidence for the stability conclusions comes from lower level studies that have relatively short-term follow-up (12 months). It is important to compare 1 vs 2-jaw surgery, in terms of effectiveness and stability, as well as morbidity, risks, and costs.
(1) Baccetti T, Franchi L, McNamara JA Jr. Cephalometric variables predicting the long-term success or failure of combined rapid maxillary expansion and facial mask therapy. Am J Orthod Dentofacial Orthop. 2004;126:16-22;
(2) Franchi L, Baccetti T, Tollaro I. Predictive variables for the outcome of early functional treatment of Class III malocclusion. Am J Orthod Dentofacial Orthop. 1997;112:80-86.