Histological changes induced by 15 F CO₂ laser microprobe especially designed for root canal sterilization; in vivo study

Till now, no suitable delivery fiber 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 designed a microprobe that reaches closer to the apex, distributing the energy density to a smaller area of the root canal, thus favorably increasing the thermal effects. The 15 F CO₂ microprobe is a flexible, hollow, metal fiber, 300 μm in diameter and 20 mm in length, coupled onto a handpice, with the following radiation parameters: wavelength-10.6 μ m; pulse duration-50m, sec; energy per pulse 0.25 joule; energy density-353.7J/ cm² per pulse; power on tissue-5W. The study was conducted on 30 vital maxillary or mandibulary; central, lateral, or premolar teeth destined for extraction due to periodontal problems. 20 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. Histological examination of the laser treated teeth showed coagulation necrosis and vacuolization of remaining pulp tissue in the root canal periphery. Primary and secondary dentin appeared normal, in all cases treated with 15 F CO₂ laser. Gramm stain and bacteriologic examination revealed complete sterilization. These results demonstrate the unique capabilities of this special microprobe in sterilization of the root canal, and no thermal damage to the surrounding tissue.