Oral Appliance, Gender, and Environmental Effects on Jaw Muscle Activities

Objectives: To elucidate the effects of mouth guard splints on jaw muscle activities during exercise, Duty Factors (DF, % time of muscle activity out of total recording time) were measured. Specific aims were to determine if DFs during exercise were affected by oral appliance condition (splint, none, sham), gender (females, males), and environment (home, laboratory).
Methods: Five females and five males gave informed consent and completed study protocols. Surface electromyography (EMG) of right masseter and anterior temporalis muscles were recorded from subjects during standardized biting and exercise protocols without appliances at two repeated laboratory sessions. Subjects also self-recorded EMG during 6 days at home while performing the exercise protocol with and without appliances, twice for each condition. Conditions were randomly assigned and different each day. Laboratory EMG versus bite-force data were plotted and linear regressions were used to calculate average EMG thresholds for 20 N bite-forces (T20N_ave). DFs during exercise at different %T20N_ave were determined from laboratory and home EMG. ANOVA and Rank Sum examined effects of condition, gender, and environment on DFs, followed by post hoc tests, where significance was defined by p<0.05.
Results: At thresholds ≤5 N, mean DFs for both muscles and genders were 2.4-times and significantly lower during exercise with splints (5.3%) compared to without splints (12.7%). No trends existed at higher thresholds or for sham results. Mean DFs during exercise were 2.0-times and significantly lower in males (5.8%) than females (11.4%) for all home conditions except sham use. At thresholds ≤5 N, mean DFs during exercise for both muscles were 6.0-times and significantly lower in home (11.8%) than laboratory (70.4%) environments.
Conclusions: DFs during exercise were lower with splints compared to without splints, in females compared to males, and in home compared to laboratory environments. Supported by UMKC SOD Summer Scholars Program.