The Effect Of The Dual Wavelength Laser On Sterilization Of Enterococcus Faecalis Within Root Canals

Objective:To investigate the effect of dual wavelength laser on sterilization of Enterococcus faecalis within root canals and to provide theoretical basis for the clinical application of the dual wavelength laser.Methods:The standard bacterial strain of the Enterococcus faecalis ATCC29212 was cultured. EfaA gene which was a virulence gene of Enterococcus faecalis was extracted. EfaA genes were transferred into plasmids. Recombinant plasmids were diluted as ten-times step. The ten-times step dilution recombinant plasmids were amplified by the Real-time Quantitative PCR technique and a standard curve was built.The crowns part of the 45 one root canal extracted teeth were decoronated and roots standardized to a length of 15 mm. The root canals were prepared by step-back technique to 35# K file. The concentration of the Enterococcus faecalis solution was adjusted at 2 MacFarland to contaminate the extracted teeth. The 45 teeth were divided into five groups randomly after they were infected 21 days, each group had 9 samples. A sample of each teeth was taken by paper point before the teeth were disposed by different methods. The specimens of group A were subjected to chemo-mechanical preparation using 5.25% NaCIO and irradiated by the dual wavelength laser. The specimens of group B were treated using the dual wavelength laser and physiological saline. The specimens of group C were prepared by using 5.25% NaOCl and ultrasonic. The 5.25% NaCIO sulotion was used for chemo-mechanical preparation of group D. Group E was irrigated by physiological saline as a control group.The counts of residual Enterococcus faecalis were detected. The root was splitted and the root canal surface was exposed which were used for investigation of scanning electron microscope(SEM).Results:The counts of the Enterococcus faecalis reduced after the teeth were disposed by different methods obviously. The counts of the residual Enterococcus faecalis had statistical difference between group A and C, C and D, D and E, B and E (P< 0.05). The group of laser dual wavelength laser and NaCIO had the best efficiency in sterilizing root canal and removing smear layer.Conclusion:1.The Er:YAG/Nd:YAG dual wavelength laser combined with physiological saline had effect on eliminating root canal infection obviously but it could not remove the smear layer;2. The Er:YAG/Nd:YAG dual wavelength laser combined with NaCIO could not only sterilize bacteria in dentinal tubule but also could remove the smear layer thoroughly.