Large versus small mandibular counterclockwise rotation during bimaxillary surgical correction of class II deformities-a retrospective CBCT study on skeletal stability.

Abstract

Postsurgical skeletal relapse is a concern for class II deformities corrected with counterclockwise rotation of the occlusal plane. Therefore, the aim of this study was to compare the skeletal stability between large and small counterclockwise rotational advancement of the mandible in patients with skeletal class II deformity. This retrospective study included 50 adult patients with skeletal class II deformity corrected by Le Fort I setback and bilateral sagittal split osteotomy counterclockwise rotational advancement. Patients were divided into two groups, according to the amount of counterclockwise rotation: small rotation (n = 25) and large rotation (n = 25). Serial cone beam computed tomography scans were analyzed to identify skeletal and dental position from presurgery to at least 12months postsurgery. Changes in the facial skeleton (maxilla and mandible) and teeth (central incisor and first molar) were determined for six skeletal and four dental landmarks by measures before treatment (T0) and 1week postsurgery (T1), and from T1 to at least 12months postsurgery (T2). A relapse was found both after large and small rotational advancement of the mandible (pogonion: 1.0 (2.4) mm and 1.4 (3.0) mm, respectively). The result was statistically significant (both p< 0.05) and was with less than 1.5mm clinically acceptable. There were no between-group differences in the postsurgical horizontal and vertical mandibular stability. The results suggest that counterclockwise rotational advancement of the mandible using bilateral sagittal split osteotomy is a clinically stable procedure. The amount of rotation does not affect the postsurgical stability of the mandible. The findings help clinicians better understand the surgical and postsurgical changes of the skeleton and teeth after counterclockwise rotational advancement of the mandible for class II deformity.