Preliminary investigation of the histological effects of laser endodontic treatment on the periradicular tissues in dogs.

This study was conducted to determine the biological effects on the periradicular tissues of Nd:YAG laser endodontic treatment in dogs. Twelve vital teeth (24 roots) of two mongrel dogs were randomly selected to receive conventional or Nd:YAG laser endodontic treatment. Endodontic therapy was performed on the second, third, or fourth, right or left, mandibular premolars. The teeth were evaluated radiographically and histologically at 1, 15, and 30 days after endodontic treatment. The remaining teeth served as untreated controls. The results of this study revealed laser treatment causes cell necrosis in the periodontal ligament 1 day after treatment. Conventionally prepared teeth displayed no evidence of cell necrosis in the periodontal ligament. At 15 days posttreatment, both the laser and conventionally treated teeth showed increased size and numbers of osteocytes and osteoclasts in the periradicular bone. Additionally, laser-treated teeth showed signs of initial bone resorption. At 30 days posttreatment, conventionally treated teeth began to return to normal morphology. The laser-treated teeth exhibited ankylosis, cemental lysis, and major bone remodeling.