Effects of prolonged gum chewing on pain and fatigue in human jaw muscles

Gum chewing has been accepted as an adjunct to oral hygiene, as salivary st imulant and vehicle for various agents, as well as for jaw muscle training. The aim of this study was to investigate the effects of prolonged gum chew ing on pain, fatigue and pressure tenderness of the masticatory muscles. Fi fteen women without temporomandibular disorders (TMD) were requested to per form one of the following chewing tasks in three separate sessions: chewing a very hard gum, chewing a soft gum, and empty-chewing with no bolus. Unil ateral chewing of gum or empty chewing was performed for 40 min at a consta nt rate of 80 cycles/min. In each session, perceived muscle pain and mastic atory fatigue were rated on visual analog scales (VAS) before, throughout. and after the chewing task. Pressure pain thresholds (PPTs) of masseter and anterior temporalis muscles were assessed before and immediately after the chewing tasks, and again after 24 h. The VAS scores for pain and fatigue s ignificantly increased only during the hard gum chewing, and after 10 min o f recovery VAS scores had decreased again, almost to their baseline values. No significant changes were found for PPTs either after hard or soft gum c hewing. The findings indicate that the jaw muscles recover quickly from pro longed chewing activity ill subjects without TMD.