AN EVALUATION OF THE BACTERICIDAL EFFECT OF THE ND-YAP LASER

The aim of this in vitro study was to compare the efficacy of a classi cal irrigant with that of a laser in disinfecting a contaminated root canal. Thirty canals of extracted single-root teeth were prepared with files to size #20. The teeth were sterilized with Germispad((R)) (Spa d, France) for 30 min and then inoculated with Streptococcus mitis ATC C 33399. By randomization, the teeth were divided into six groups of f ive teeth each. In the first group, teeth were neither inoculated nor prepared. This was the sterility control group (1). In the second grou p (2) teeth were inoculated without any preparation: as positive contr ols. The third group was inoculated and then hand-instrumented with fi les to size #30 with 5.25% NaOCl as irrigant. This was the hand instru mentation group. The other groups were prepared with hand instrumentat ion with files to size #30, using sterile water as an irrigant, and th e canal was then lased with different frequencies as follows: group 4, frequency of 5 Hz and power of 260 mJ; group 5, frequency of 10 Hz an d power of 310 mJ; and group 6, frequency of 30 Hz and power of 300 mJ . After experimentation, the residual colonies were counted. The resul ts indicated that (i) the treatment with NaOCl and manual instrumentat ion effectively inhibited the growth of Streptococcus mitis ATCC 33399 ; and (ii) the antibacterial effect of the Nd:YAP laser depended on th e frequency. Only a frequency of 30 Hz of the Nd:YAP laser inhibited t he growth of Streptococcus mitis ATCC 333999.