The Effects of Intracanal Irradiation of Pulsed Nd: YAG Laser on the Periradicular Tissues in the Dog

Abstract

The aim of this study was to histopathologically investigate the effects of pulsed Nd: YAG laser irradiation on the periradicular tissues when applied in the root canal of the dog.Six adult mongrel dogs were anesthetized and the tooth pulps of the upper and lower premolars were extirpated. Each root canal was cleaned and shaped to a final apical file size #55. Non-irradiated root canals were served as control.The laser irradiation (100mJl0pps, 100mJ20pps, 100mJ30pps, 200mJ10pps and 200mJ20pps) was performed under an up-and-down motion in the root canal between the apical and cervical portion with an optical fiber (∅=400μm) for 30 sec. After the irradiation, a small cotton pellet soaked with formalin cresol was placed in the pulp chamber and the access cavity was filled with glass ionomer cement. The animals were sacrificed at 7 and 28 days postoperatively.The results were as follows:1. At 7 days postoperatively, no histopathological difference was found between the control and 100mJ10pps group. On the other hand, carbonization and defects of the root canal wall were observed in all laser-treated groups except the 100mJ10pps group.2. At 28 days postoperatively, alveolar bone resorption was often observed again in all laser-treated groups except the 100mJ10pps group. Furthermore, in the 100mJ20pps group, dentoalveolar ankylosis was observed in the periradicular tissues, and severe external root resorption was frequently seen in the 200mJ20pps group. However, in the 100mJ10pps group, the degree of inflammation in the periradicular tissues was similar to the control.3. It was concluded that pulsed Nd: YAG laser with irradiation energy less than 100mJ10pps could be used safely in the root canal of the dog.(J. Jpn. Soc. Laser Dent. 7: 12-21, 1996 Reprint requests to Dr. SEKINE)