Relationship between three-dimensional position change of mandibular proximal segment and temporomandibular disorders after intraoral vertical ramus osteotomy in skeletal Class III malocclusion with asymmetry

Abstract

The purpose of the present study was to compare pre- and post-operative changes in temporomandibular joint (TMJ) sounds and pain in patients who had undergone orthognathic surgery (LeFort I osteotomy and intraoral vertical ramus osteotomy) for correction of skeletal Class III malocclusion with facial asymmetry, and to identify skeletal differences associated with these symptoms. Preoperative (T1) and 1-year postoperative (T2) 3-dimensional CT (3D CT) imaging of 29 patients with skeletal Class III with facial asymmetry were obtained and measured. These subjects were grouped Group Ia (improved /maintained joint sound) and Group Ib (worsened joint sound), as were grouped Group IIa (improved /maintained TMJ pain) and Group IIb (worsened TMJ pain) according to changes of TMD clinical sign after surgery. Horizontal and vertical asymmetry, configuration of the condyle and fossa, preoperative (T1) mandibular proximal segment measurements, postoperative (T2) mandibular proximal segment measurements, and pre- and post-operative mandibular proximal segment changes [△T(T2-T1)] were compared and analyzed with the following results: 1. No statistically significant differences were noted in horizontal and vertical asymmetry between either group for TMJ sound and pain.2. Preoperatively (T1), the coronal condylar long axis angle on the non-deviated side was greater in Group Ib (worsened joint sound) than Group Ia (improved/maintained joint sound) (p<0.01). There was also a greater difference in coronal condylar long axis angle between each side in Group Ib (p<0.05).3. Postoperatively (T2), the horizontal condylar angle was noted to be smaller on the deviated side than the non-deviated side in Group Ib compared to Group Ia (p<0.01). Also, the coronal condylar vertical axis angle was smaller in Group Ib (p<0.05).4. There was a greater increase in horizontal condylar angle on the non-deviated side than the deviated side in Group Ib compared to Group Ia when pre- and postoperative changes [△T(T2-T1)]were compared (p<0.01).5. In the postoperative period (T2), Group IIb (worsened TMJ pain) had a smaller horizontal condylar angle on the deviated side compared to the non-deviated side (p<0.05), and a smaller A-B distance (superior joint space) compared to Group IIa(improved/maintained TMJ pain) (p< 0.05).The results of this study indicate that in skeletal Class III patients with asymmetry corrected with IVRO, a smaller postoperative horizontal condylar angle on the deviated side and less inferior movement of the deviated condyle are associated with worse TMJ sound and pain.