Orthodontic Pain Induced Sensitization of Trigeminonociceptive System of Patients Undergoing Fixed Orthodontic Treatment

Pain is a complex sensory experience and often accompanies orthodontic conditions and interferes with its management. Orthodontic pain induced by application of orthodontic appliances and traction forces on maloccluded teeth, is typically transient (peaks in 24 hours and subsides within a week), alters sensory perception and normal motor activities such as chewing and talking. The present study was aimed to record thermal sensitivity and motor activity of masseter muscle in patients undergoing fixed orthodontic therapy at 3 time points i.e. before start of treatment (Day 0), at 24 hours (Day 2) and a after a week (Day 7). Pain rating by visual analog scale, Quantitative sensory testing (thermal detection, pain threshold and tolerance threshold for both cold and hot stimuli) and surface electromyography (amplitude and time to fatigue) were recorded for masseter muscle. D'Agostino-Pearson and Friedman's test were applied for determining normality and for comparisons respectively. Twenty eight patients (17 males, 11 females) mean age (17.88 +/- 3.92 years) were recruited from Orthodontics and maxillofacial deformity department. We found significant changes in cold pain perception and cold pain tolerance at Day 2, when compared to Day 0 and Day 7. At Day 2 amplitude of maximum voluntary contraction and time to fatigue were significantly lower than Day 0. All other parameters such as thermal thresholds were comparable at all the time points. The findings suggest that orthodontic procedures causes transient sensitization of the trigeminal nociceptive system. Quantitative assessment of somatosensory and motor function may help in better understanding of time kinetics and mechanism of orthodontic pain in order to plan and modify orthodontic treatment based on patients thresholds and responses.