Local application of melatonin into alveolar sockets of Beagle dogs reduces tooth removal-induced oxidative stress

Background: The antioxidant and anti-inflammatory hormone melatonin is secreted by saliva into the oral cavity, where it may protect the mucosal and gingival tissues from radical damage. To date, no studies have addressed the potential beneficial role of melatonin in the acute inflammatory response that follows oral surgical interventions, especially tooth extractions. The aim of this study was to determine whether tooth extraction induces changes in plasma oxidative stress levels, and whether melatonin treatment may counteract these changes. Methods: Maxillary and mandibular premolars and molars of 16 adult Beagle dogs were extracted under general anesthesia. Eight dogs were treated with 2 mg melatonin placed into the alveolar sockets, whereas the other eight dogs received only vehicle. Lipid peroxidation (LPO) and nitrite plus nitrate (NOx) levels were determined in plasma, whereas glutathione (GSH) and glutathione disulfide (GSSG) levels and glutathione peroxidase (GPx) and reductase (GRd) activities were measured in red blood cells before and 24 hours after tooth extraction. Results: Removal of the premolars and molars caused a significant rise in plasma LPO, and NOx levels and in the erythrocyte GSSG/GSH ratio, whereas melatonin treatment restored the normal values of these parameters. Also, melatonin slightly increased erythrocyte GRd activity without changing GPx activity. Conclusion: For the first time to our knowledge, the results show that during the immediate postoperative period following tooth extraction, there is a significant increase of oxidative stress, which is counteracted by the administration of melatonin into the alveolar sockets.