Occlusal contacts are affected by experimental jaw muscle pain

Objective: Aim of the study was to measure the effect of an experimental jaw muscle pain on number and position of posterior occlusal contacts. Methods: Eleven adult voluntary subjects (nine male, two female, age 25.2±2.3) were enrolled in this randomized cross-over study. Each subject participated in two experimental sessions (separated by 30 days) in which he/she received an injection in the right masseter muscle. Subjects were randomized with respect to the sequence of the substance injected, hypertonic (5.0%) or isotonic saline solution (0.9%), used respectively as painful and control substance. Three occlusal bite records at the maximal intercuspal position were obtained during each experimental session: before (baseline), during and ten minutes after the end of injection. Occlusal records were put on lower casts and posterior contacts were reported by different colors (black for baseline, red for intermediate and green for final contacts) and counted. Difference in color was assumed to be difference in position, and the intermediate contacts were consequently classified as confirmed, disappeared or new contacts. Repeated measures ANOVA was used to compare the overall number of contacts among groups and the number of contacts of different colors. Results: Means and standard deviations of number of contacts are reported in table. No significant difference was found between the overall number of occlusal contacts, but a significant difference (p=.03) was found between contacts according to different colors. That means the overall number of contacts did not change, but the position did. Conclusion: Within the limits of the present study (first of all the small number of subjects), an experimentally induced jaw muscle pain, under controlled conditions, seems to affect the position but not the number of posterior occlusal contacts.