A cone beam computed tomography study on the osseous morphology of temporomandibular joint with free loss of posterior teeth

Objective: The purpose of this retrospective study is to explore the association between free loss of posterior teeth (FLP) including bilateral (BFLP) and unilateral (UFLP) free loss of posterior teeth and the osseous morphology of temporomandibular joint (TMJ). Design: The condylar volume(V) and surface area(S), condylar mediolateral diameter (CD), horizontal condylar angle (HCA), glenoid fossa depth (GFD) and articular eminence inclination (AEI) of the bilateral TMJs were measured by using cone-beam computed tomography (CBCT) and Mimics software. The study included 120 FLP patients (UFLP=60, BFLP=60) and 60 controls with complete dentition. The differences between and within groups were statistically analyzed by SPSS 26.0. A two-way ANCOVA was employed to analyze the interaction effects among FLP, sex, and age on TMJ osseous morphological changes. Results: In the UFLP group, both CD and AEI of the missing side were greater than those of the non-missing side (p < 0.05). Between groups, the GFD of the control group was significantly greater than those of the BFLP group and the missing side and non-missing side of the UFLP group (p < 0.05). Two-way ANCOVA demonstrated significant sex-based differences in TMJ morphology (V, S, CD, GFD, AEI; p < 0.05), with pronounced FLP x sex interactions for V, S, and CD (p < 0.001). Age predominantly influenced GFD (p < 0.001), surpassing FLP and sex effects (p < 0.05). Conclusions: FLP was associated with shallower glenoid fossa morphology. Patients with UFLP showed asymmetric TMJs, with reduced CD and a flatter articular eminence on the non-missing teeth side. FLP-associated TMJ changes require careful consideration of sex and age factors.