Abstract: Objective: To investigate the influence of previous occlusal interference on masticatory muscle hyperalgesia induced by secondary occlusal interference in rats. Methods: Repetitive occlusal interferences were obtained by bonding a 0.4 mm thick metal crown on the upper first molar in rat and removing it after two or four days. The bilateral head withdrawal thresholds were measured at multiple time points. Results: Eight days were needed for the thresholds to recover to baseline after the removal of the first occlusal interference which lasted for two days, and 10 days were needed after two occlusal interferences which both lasted for two days. And it took respectively 19 days and 12 days for the thresholds to recover to baseline after the removal of the second occlusal interference which lasted for 4 days following the first occlusal interference which lasted for 2 days or following sham operation. Conclusion: The first occlusal interference which lasted for 2 days facilitated masseter hyperalgesia induced by the second occlusal interference which lasted for 2 or 4 days in postponing the recovery time without increasing the severity of masseter hyperalgesia. This study successfully established an animal model of repetitive occlusal interference-facilitated masticatory muscle pain.

Key words: Masticatory muscle, Hyperalgesia, Traumatic, Rats