• Thalerngsak Samaksamarn D.D.S., Grad. Dip. in Clin. Sc. (Endodontics)
• Chantavat Sutthiboonyapan D.D.S., Grad. Dip. in Clin. Sc. (Endodontics), M.S., Diplomate, Thai Board of Endodontics
• Patchara Pipattanagovit D.D.S., M.S
• Oranart Matangkasombut D.D.S., Ph.D.

Objective To compare the antibacterial effect of the erbium, chromium: yttrium-scandium-galliumgarnet
(Er,Cr:YSGG) laser irradiation with two irrigating solutions in root canals of extracted human
teeth.

Materials and methods One hundred and twenty-five extracted single-rooted teeth were collected.
The canals were then enlarged with K files to size 50 using crown-down technique and randomly
assigned into four experimental groups of 30 teeth each and five teeth for sterility control group. After
sterilization, all roots except the sterility control group were inoculated with 10 microlitres of a known
concentration of Enterococcus faecalis ATCC29212 and incubated at 37 ÌC for 48 hours. The first group
was used as a negative control receiving no treatment. The second group and third group were irrigated
with 2.5% sodium hypochlorite (NaOCl) solution and 2% chlorhexidine (CHX) solution for 10 minutes respectively. The last group was irradiated with the Er,Cr:YSGG laser at 1.5 watts output power with no air and water using four lasing cycles of 10 seconds each. After treatment, sterile normal saline solution was filled into the canals and the walls were then circumferentially filed with H-file size 50. The content was then transferred and plated on tryptic soy agar immediately. All plates were incubated at 37 °C for 24 hours. The colony-forming units were counted, and the quantitative results were subjected to an One-Way ANOVA test and Tamhaneûs Test.

Results The differences in the mean number of viable colonies between the control and the other
groups were statistically significant different (p < 0.05). Comparing among the treated groups, the
mean Log colony forming units values obtained after Er,Cr:YSGG laser irradiation were statistically
significantly higher than 2.5% NaOCl and 2% CHX group (p < 0.05). However, there was no significant
difference between the 2.5% NaOCl and 2% CHX group (p > 0.05).

Conclusion It can be concluded that Er,Cr:YSGG laser irradiation can reduce the viable microbial
population in root canals to a certain extent but is less effective than irrigating with 2.5% NaOCl and
2% CHX solutions.

(CU Dent J. 2008;31:125-34)