The stability of occlusal plane rotation during orthognathic surgery

Samuel C. Bennett

doi:10.21307/aoj-2020-088

Abstract

Abstract Background Considered rotation of the occlusal plane and the maxillomandibular complex during orthognathic surgery is an approach that enables optimisation of the functional and aesthetic outcomes of surgical-orthodontic treatment for the correction of a variety of dentofacial deformities. Objectives The objectives of this study are to: (1) retrospectively evaluate the stability of clockwise and anti-clockwise rotation of the occlusal plane during orthognathic surgery, and (2) compare the findings with the stability of orthognathic surgery in which no significant occlusal plane rotation occurs. Aims and methods Data were collected from a sample of 31 adult patients (22 females and nine males) treated by one orthodontist in private practice and at the University of Western Australia from 1992–2008. Patients received a Le Fort I osteotomy and BSSO to reposition the maxilla and mandible, respectively. The patients were separated into three groups defined by no occlusal plane rotation; clockwise occlusal plane rotation; or anti-clockwise occlusal plane rotation. Lateral cephalograms were taken at four time periods during treatment: T1 (pre-surgery), T2 (immediately post-surgery), T3 (six weeks post-surgery), and T4 (longest follow-up). The cephalograms were digitised and analysed using a customised cephalometric analysis (QuickCeph Studio, CA, USA) and landmarks were transferred via cranial base and maxillary superimpositions for each patient from T1 sequentially to T4. Results Clockwise rotation of the occlusal plane was highly stable one year following surgery and showed comparable results with cases treated without occlusal plane rotation. Anti-clockwise rotation of the occlusal plane was less stable and showed significant relapse of the occlusal plane angle towards the pre-surgical value during the post-surgical observation period. Conclusion Clockwise rotation of the occlusal plane during orthognathic surgery appears highly stable. Anti-clockwise occlusal plane rotation during orthognathic surgery appears less stable. Further studies are needed to evaluate the longer-term stability of clockwise and anti-clockwise rotation of the occlusal plane during surgical-orthodontic treatment.

Highlights

Dentofacial deformities severe enough to require surgical intervention often require bimaxillary surgery to optimise the functional and aesthetic outcomes of treatment.[1,2,3,4] Depending on the patient’s facial morphology, it is sometimes necessary and/or desirable to rotate the maxillomandibular complex (MMC) and occlusal plane (OP) during surgery
Intra-Class Correlation (ICC) was used to evaluate the reliability of the data produced by the cephalometric superimposition and digitisation methods applied during the study
The present results indicate that a significant degree of relapse may follow an anti-clockwise rotation of the occlusal plane during surgical-orthodontic treatment, which is the possible result of postsurgical changes related to settling of the occlusion.[9,10]

Summary

Introduction

Dentofacial deformities severe enough to require surgical intervention often require bimaxillary surgery to optimise the functional and aesthetic outcomes of treatment.[1,2,3,4] Depending on the patient’s facial morphology, it is sometimes necessary and/or desirable to rotate the maxillomandibular complex (MMC) and occlusal plane (OP) during surgery. Class II type of malocclusions because it enabled a reduction in chin prominence and improved stability.[7] Clockwise rotation of the occlusal plane during surgery produces a tapering of facial form that is aesthetically beneficial, in brachyfacial female patients.[8] it may be more advantageous to rotate the occlusal plane in an anti-clockwise direction during surgery to gain improvements in airway volume and horizontal chin projection, especially in patients with severe chin retrusion. Whilst the potential functional and aesthetic advantages gained by surgery involving clockwise rotation of the occlusal plane are well documented, there is little literature supporting the long-term stability of anti-clockwise occlusal plane rotation during orthognathic surgery.[9,10]. Further studies are needed to evaluate the longer-term stability of clockwise and anti-clockwise rotation of the occlusal plane during surgical-orthodontic treatment. (Aust Orthod J 2017; 33: 82-96)

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Discussion

Conclusion