Occlusal Factors associated with Temporomandibular Disorder based on a Prospective Cohort Study of Young Adults

Abstract

Purpose: To determine the relationship between temporomandibular disorders (TMD) and the occlusal contact pattern, we conducted occlusal analysis in a prospective cohort study.Methods: One hundred forty-six volunteers consisting of 98 males and 48 females with a mean age of 20.0±1.9 years selected from the dental students of Iwate Medical University were enrolled for the study. All the subjects were asked to fill out a self-administered questionnaire to screen their general and oral health conditions, and then clinical examination, including evaluation of the occlusal contact pattern, was conducted during the first year. A second clinical examination was repeated 2.5 years later to ascertain the incidence of symptoms of TMD. The natural course of TMD symptoms in the 128 subjects were as follows: 66 were classified in the symptom-free group, 18 in the symptom incidence group, 14 in the symptom remission group, and 30 in the symptom continuation group. Then, the occlusal contact patterns during lateral mandibular excursion were classified into five types: (1) canine protected occlusion and group function (CG; n=192), (2) bilateral occlusal guidance (BG; n=10), (3) working side molar guided occlusion (WM; n=45), (4) non-working side molar guided occlusion (NM; n=4), and (5) incisal guided occlusion (IG; n=5).Results: In the second examination, 18 out of the 84 subjects (21.4%) who showed no symptoms at the time of enrolment into the study reported TMJ click and⁄or pain. Of the total, 23, 11, 1, and 1 subjects with symptoms of temporomandibular joint origin were classified as having the CG, WM, NM, and BG pattern of occlusal contact, respectively. With CG as the standard, the relative risk of TMD in subjects shown the WM pattern was 2.79 (95%CI: 1.16-6.70).Conclusion: Since the group showing the working side molar guided occlusion pattern showed a high risk of future development of TMJ click and⁄or pain, lateral excursion guidance may be a contributing factor for the development of TMD.