Objective: To analyze occlusal contact areas on the working and nonworking sides during unilateral mastication.
Methods: Eighteen subjects without any temporomandibular disorder (TMD) symptoms participated in the present study. The subjects were presented with 3 g gum for right masticating. Chewing movement was simulated using virtual craniofacial movement simulation system. Then occlusal contact areas were calculated at four selected moments during the closing phase in the third chewing cycle: the occurrence of occlusal contact, one third time, two thirds time, the intercuspal occlusion.
Results: During the closing phase in the third chewing cycle, the total occlusal contact areas on working side increased from (9.3+/-0.4) mm2 to (39.2+/-1.2) mm2, and that on nonworking side increased from (2.3 +/-0.5) mm2 to (40.3+/-1.2) mm2. At the occurrence of occlusal contacts, occlusal contact areas of the first and second mandibular molars were on average (3.7+/-0.2) mm2 and (3.5+/-0.2) mm2 on working side, and (0.5+/-0.2) mm2 and (1.2+/-0.3) mm2 on nonworking side, respectively. However, when the mandible moved to the intercuspal position, their areas were sharply increased to (14.8+/-0.7) mm2 and (13.9+/-0.4) mm2 on working side, and (13.6+/-0.5) mm2 and (12.1+/-0.5) mm2 on nonworking side, respectively. In addition, nonworking-side contacts were observed for 12 subjects at the occurrence of occlusal contacts, and for all subjects at two thirds time.
Conclusion: This paper provides a new method useful for analyzing occlusal contacts during functional movements. This study revealed the pattern of occlusal contacts during the closing phase in the chewing cycle. Moreover, it was confirmed that nonworking-side contacts occurred during unilateral mastication.