Nd:YAG laser irradiation inactivates endotoxins of dental root dentine

Endotoxins are responsible for important systemic and local reactions that could compromise the endodontic treatment success. The calcium hydroxide even with limitations is the only effective option among the irrigating solutions and intracanal medications on the endotoxin reduction in the dentinal tubules. Objectives: This study evaluated the Nd:YAG laser irradiation effect on the inactivation of endotoxins inoculated in the root canal dentine. Methods: Twenty-four unirradicular teeth were used. The root canals were prepared using a conventional serial technique. Then, they were mounted between two chambers and sterilized using Gamma irradiation. Endotoxin from E.coli (16UE/ml) was placed into the upper chamber. Forty-eight h later, the root canals were irradiated using a Nd:YAG laser (1,064nm, pulse width 120µs, core fiber diameter of 320µm, 1.5W, 15Hz, fluence of 124J/cm2 during 7 s with relaxation time interval of 30 s and in contact mode). Two kinematics of irradiation were used: helicoidal technique and oscillatory technique. Positive and negative non irradiated groups were used. After irradiation the dental roots with the upper chamber were transferred to a sterile lower chamber containing water. After an incubation of 72 h at room temperature, aliquots of the lower chamber water were tested by the LAL turbinemetric kinematics Pyrotell-T test for measuring the endotoxin concentration. The data were compared by Kruskal-Wallis' test complemented by the Dunn's test (p ≤ 0.005). Results: The endotoxin concentrations of the irradiated samples, regardless the irradiation techniques applied, were similar. Moreover, these concentrations were also similar to those of negative controls and significantly smaller than those of positive controls (p=0.0271). Conclusion: The Nd:YAG laser irradiation under this experiment conditions was effective on the inactivation of endotoxin present in the dental root canal lumen and all the way through the root dentine and cement . This research was supported by Fapesp grants number 2005/57550-6