Effect Of Neuropathic Orofacial Pain On Jaw-Muscle Activity During Chewing

Objectives: To determine whether there is a relation between the report of  neuropathic orofacial pain (NOP) on muscle activity during free (casual) and standardized chewing tasks. Methods: Fourteen subjects with a diagnosis of NOP (4 males and 10 females), having a  mean age of 63.0±9.5 years  (range 49-76) and 15 age and gender matched healthy subjects for control (5 males and 10 females) were recruited for the study.  NOP subjects had a history of pain for 3-36 years. but  pain free on day of experiment. In each subject, surface electrodes were placed bilaterally over anterior temporalis and masseter muscles and unilaterally over right digastric muscle. Electromyographic activity was amplified, filtered and digitized,and jaw movement was recorded with a jaw tracking system during free chewing (natural) and standardized chewing of gum on the right side of the mouth. The standardized and free chewing tasks were repeated a minimum 2 times and each trial lasted approximately 20 seconds. Results: A comparison of the neuropathic pain group vs. pain-free control group has demonstrated jaw muscle activity that depends on the task kinematic variables (displacement at every 0.5 mm interval). A significanct group displacement interaction (p<0.05) found on Right Masseter and left Masseter for free chewing and right temporalis for standardized chewing during jaw opening and for right temporalis jaw closing of free chewing. Conclusions: The results indicate an effect of history of NOP pain at displacement on muscle activity of elevator and depressor muscles varied between participants with no pain and chronic pain condition, which is suggestive that there is a long-term effect of neuropathic orofacial pain on jaw muscle activity. Acknowledgement: NHMRC Australia, ADRF, ADA (NSW Branch), Hamdard University, Pakistan