Factors Associated with Chewing Side Preference in a Dentate Population

Objectives: The aim of this study was to determine whether handedness or asymmetry of occlusal characteristics, muscular force and temporomandibular disorders (TMD) can explain chewing side preference in a dentate population. Methods: One hundred and seventeen dentate adults participated in this cross-sectional study. Static and dynamic occlusal characteristics were determined at maximal intercuspal position and at right and left lateral excursions of 1.5 mm by scanning interocclusal records and analyzing them using image software. Unilateral maximum bite force and finger-thumb grip force were measured by means of a gnathodynamometer. TMD were assessed according to the Research Diagnostic Criteria for TMD. Chewing side preference was determined by observing the direction towards which the jaw was moved while each subject chewed three pieces of silicon for 20 chewing strokes, repeated over for 5 trials. Asymmetry or side difference variables were calculated as the difference between right-hand-side values and left-hand-side values for all parameters. Stepwise multiple linear regression was performed to examine whether side difference variables explain chewing side preference. Results: Fifty-nine subjects (50.4%) chewed on the right, 15 (12.8%) chewed on the left, and 43 (36.8%) chewed on both sides. Ten subjects (8.5%) were left-handed. There was no relationship between preferred chewing side and handedness. Significant relationships were observed between chewing side preference and side differences in bite force, occlusal contact area, Angle class, type of dynamic occlusion and presence of disc displacement with reduction (P<0.05). Stepwise multiple linear regression showed that side differences in bite force, occlusal contact area and disc displacement were the factors related to the preferred chewing side (adjusted R square =0.22). Conclusions: Asymmetry of bite force and occlusal contact area at intercuspal position together with the presence of disc displacement in the TMJ explained 22% of the variation in chewing side preference in a dentate population.