The purpose of this study was to assess the efficacy of Nd:YAG laser i
rradiation in disinfecting the root canal system. Seventy-five teeth w
ere uniformly instrumented and sterilized, and their root canals were
infected for 60 min with an overnight culture of Enterococcus faecalis
in Tryptic Soy Broth. The teeth were divided into 6 groups: 1 - non-i
nfected controls; 2 - infected controls; 3 - infected, laser treated;
4 - infected, laser dummy (dye only); 5 - infected, laser dummy (dye a
nd air-water spray); 6 infected, NaOCl-treated (reference group). Afte
r treatment, the root canals were dried and dentinal shavings removed
for a posttreatment culture. Quantitative analysis of bacteria survivi
ng the various treatments were performed, and the bacterial counts for
each group were compared. SEM analysis of teeth split longitudinally
was used to illustrate the effect of treatment on the smear layer and
on surface bacteria. Nd:YAG laser irradiation (group 3) significantly
reduced the number of bacteria while NaOCl irrigation (group 6) effect
ively disinfected the canals.