Genetic basis for individual variation in pain perception among endodontic patients

Catechol-O-methyltransferase (COMT), Cyclooxygenase (COX) 1 and 2 are enzymes that have been implicated in the modulation of pain. Previous studies have shown that human genetic variants coding for low COMT activity are correlated with increased experimental pain sensitivity and risk of developing chronic pain disorders. The present study extends this work by examining the potential contribution of three enzymes to acute pain perception. Ninety-four patients treated by endodontic residents at University of North Carolina School of Dentistry were enrolled into a prospective cohort study. Nonsurgical root canal therapy was performed. Participants recorded pain levels for five days following treatment and completed psychological questionnaires to quantify anxiety, depression and somatization disorders. Potential predictors of postoperative pain were collected and all patients submitted saliva samples for genetic analysis. In this study, 63% of patients experienced at least mild pain after root canal therapy and 24% experienced mild to severe pain. Patient age, gender, pulpal and periapical diagnosis were not associated with postoperative pain (p>0.05). Presence of pretreatment pain was significantly correlated with higher postoperative pain (p = 0.01). Diastolic blood pressure (p = 0.024), heart rate (p = 0.02) and trait anxiety score (p = 0.036) were also correlated with postoperative pain. While no association was found between postoperative pain and COMT or COX-1 genetic variants, there is evidence of an association between COX-2 haplotype and acute postoperative pain following endodontic treatment (p = 0.025). Understanding the genetic basis of endodontic pain perception will advance our pharmacologic management of postoperative pain