Autorotation of the Mandible as Sequelae to Maxillary Intrusion

Abstract

Background: Autorotation of the mandible is a normally anticipated phenomenon following a surgical superior repositioning of the maxilla in clinical situations where patients have an excessive gummy smile. Prediction of the surgical treatment outcome following a presurgical orthodontic treatment is a critical element in the surgical treatment planning. Materials and Methods: The relevant articles were selected by hand search and electronic media (Google Scholar, PubMed, Science Direct, Medline, Embase, and Cochrane) from 1982 to 2020. All the relevant articles were properly screened, and findings were extracted from the articles. Results: It was observed that, following maxillary intrusion, mandible would eventually autorotate to take a new occlusion. Mandibular autorotation as a result of maxillary intrusion would lead to minimal shortening of the lower lip in the vertical plane. It was observed that the amount of mandibular autorotation correlates with the extent of maxillary impaction. Studies have shown that there is a passive soft-tissue response which may be attributed to the fact that no muscular detachment had been affected in the lower lip and soft-tissue chin region during the maxillary surgery. Conclusion: It is observed that there is a definite influence on the mandibular and chin positions as a result of maxillary intrusion and autorotation of the mandible. Every 1 mm of maxillary superior impaction, the chin moved 0.6 mm vertically and 0.2 mm horizontally. There is an appreciable shortening of the lower lip length.

Surgical-orthodontic approach for correcting Vertical Maxillary Excess: Case report

“…However, it can also be performed anteriorly in patients presenting with a gummy smile. 13 Since treating lip incompetence and excessive teeth exposure is a priority in patients with VME, it is important to determine the amount of maxillary impaction necessary to achieve optimal functional and esthetic results. In a previous study, it was shown that approximately 2 mm of maxillary incisors are visible with the lips at rest.…”

“…It was observed that the amount of mandibular autorotation is proportional to the amount of maxillary impaction; with every 1 mm of maxillary superior repositioning, the chin would move 0.6 mm vertically and 0.2 mm horizontally. 13 Another study revealed that an average of 5 mm-maxillary impaction would lead to a 2 mm advancement and 1.2 mm shortening of the chin when using the condyle as center of rotation for mandibular autorotation in the cephalometric predictions. 16 In our case, the maxillary impaction was combined with a BSSO for mandibular anterosuperior movement to further shorten the lower face and improve chin projection.…”