Asymmetry of dental or joint anatomy or impaired chewing function contribute to chronic temporomandibular joint disorders

Abstract

Introduction: The etiologies of most chronic temporomandibular joint disorders are unknown. However, an association between habitual chewing on a particular side and chronic temporomandibular joint disorders has been reported. The aim of this study was to investigate the differences between sides (affected vs unaffected) of biodynamic factors (including lateral dental guidance determined by dental anatomy) or condylar path angles (determined by temporomandibular joint morphology) and chewing function (physiological alternate chewing vs single habitual chewing side). The study scope was to investigate possible etiological factors to improve the understanding of temporomandibular joint disorders. The null hypothesis was that no difference would be found between sides that are or are not affected by chronic temporomandibular joint disorders in chewing function or in levels of dental or temporomandibular joint remodeling. Methods: This cross-sectional, double-blind study involved 24 adults with substantial, chronic, unilateral symptoms diagnosed as temporomandibular joint disorders. Chewing function, temporomandibular joint remodeling (using axiography) and dental anatomy (lateral guidance angles using kinesiography) were assessed. Results: Habitual chewing on one particular side was observed in 17 of 24 participants; significantly more (n = 15) chewed on the affected side than on the unaffected side (P = 0.002 in a two-tailed Fisher’s exact test; risk estimate = 4.5; 95% CI 1.326–15.277). The condylar path (CP) angle was steeper on the affected side than on the unaffected side (mean (standard deviation) = 50.52° (9.98°) versus 45.50° (7.98°); P = 0.002 in a two-tailed t-test). The lateral guidance (LG) angles were flatter on the affected side in all 24 participants. Conclusion: Our results suggest that habitual chewing on one side may be associated with increasing condylar path, with flattening lateral guidance angles, and also with chronic temporomandibular joint disorder on the habitual chewing side