Histological changes induced by CO₂ laser microprobe specially designed for root canal sterilization: In vivo study

Objective: Until now, no suitable delivery fiber has existed for CO₂ laser endodontic radiation in the apical region, where it is most difficult to eliminate the pulp tissue using conventional methods. To overcome this problem, we have designed a microprobe that reaches closer to the apex, distributing the energy density to a smaller area of the root canal and thus favorably increasing the thermal effects. Methods: A CO₂ laser microprobe coupled onto a special hand piece was attached to the delivery fiber of a Sharplan 15-F CO₂ laser. The study was conducted on 30 vital maxillary or mandibulary, central, lateral, or premolar teeth destined for extraction due to periodontal problems. Twenty were experimentally treated with pulsed CO₂ laser delivered by this newly developed fiber after conventional root canal preparation. Temperature measured at three points on the root surface during laser treatment did not exceed 38 °C. Ten teeth represented the control group, in which only root canal preparation was performed in the conventional method. Results: Histological examination of the laser-treated teeth showed coagulation necrosis and vacuolization of the remaining pulp tissue in the root canal periphery. Primary and secondary dentin appeared normal in all cases treated with 15-F CO₂ laser. Gram stain and bacteriologic examination revealed complete sterilization. These results demonstrate the unique capabilities of this special microprobe in sterilization of the root canal, with no thermal damage to the surrounding tissue. Conclusions: The combination of classical root canal preparation with CO₂ laser irradiation using this special microprobe before closing the canal can drastically change the quality of root canal fillings.