A pilot investigation of condylar position and asymmetry in patients with unilateral posterior scissors-bite malocclusion based on three-dimensional reconstructive imaging technique

OBJECTIVE: Unilateral posterior scissors-bite (uPSB) malocclusion is common clinically. This study aimed to investigate the condylar morphological alterations and condyle-fossa relationship in patients with uPSB, through cone beam computed tomography (CBCT) and three-dimensional reconstructive imaging technique. METHODS: A retrospective study was designed to comparatively analyze 95 patients with uPSB between July 2016 and December 2021. They were divided into three subgroups: 12 to 20, 21 to 30, and ≥ 31 years, according the age distribution. The morphological parameters regarding condyle, fossa, and joint space after three-dimensional reconstruction were measured and analyzed by a series of digital software. SPSS 26.0 software package was performed for statistical analysis on data sets, using paired t–test, one–way analysis of variance, Wilcoxon signed–rank sun test, Kruskal–Wallis H test, and Bonferroni correction. RESULTS: The condylar volume (CV) of scissors-bite side was greater than that of the non-scissors-bite side (CV (A) = 1740.68 ± 559.80 mm(3) > CV (N) = 1662.25 ± 524.88 mm(3), P = 0.027). So was the condylar superficial area (CSA) (CSA (A) = 818.71 ± 186.82 mm(2) > CSA (N) = 792.63 ± 173.44 mm(2), P = 0.030), and the superior joint space (SJS) [SJS (A) = 2.46 (1.61, 3.68) mm) > SJS (N) = 2.01 (1.55, 2.87) mm), P = 0.018], and the anterior joint space (AJS) (AJS (A) = 3.94 ± 1.46 mm > AJS (N) = 3.57 ± 1.30 mm, P = 0.017). The constituent ratios of the different parts of the bilateral condyles were 23% on the posterior slope, 21% on the top, 20% on the anterior slope, 19% on the lateral slope and 17% on the medial slope, respectively. CONCLUSION: Due to long-term abnormal occlusion of uPSB, the pathological bite force in temporomandibular joint would cause changes in the shape of the condyle. Among them, CV, CSA, SJS and AJS had significant changes in the scissors-bite status, which has the greatest damage to the posterior slope of the condyloid process.