Background and objectives:
To investigate the bactericidal effect of an 809 nm semiconductor laser alone, and in combination with naocl/h(2)o(2) irrigation in root canals in vitro.
Study design/materials and methods:
A total of 72 human single-rooted teeth extracted for periodontal reasons were included. the crowns were removed, the roots shortened to a length of 12 mm, and the canals enlarged up to an apical size of #50 file. the specimens were autoclaved and incubated with a suspension of streptococcus sanguinis (atcc 10556). laser irradiation was performed on a pc-controlled xy translation stage. a 200 micron optic fiber was used. twelve specimens were irradiated at a power output of 1.5, 3.0, and 4.5 w in the cw-mode. the total irradiation time was 60 seconds per canal. twelve specimens were rinsed with naocl and h(2)o(2) only, 12 were rinsed and laser treated, and 12 served as untreated controls. after laser treatment, the specimens were sonicated and the bacterial growth was examined by counting colony forming units on blood agar plates. temperature changes at the outer root surface during irradiation were registered by means of thermocouples. treated and control specimens were investigated by means of scanning electron microscopy.
Results:
Mean bacterial reductions of 0.35 log steps at a power output of 1.5 w, 1.44 at 3.0 w, and 2.84 at 4.5 w were calculated. bacterial reduction by the naocl/h(2)o(2) solution alone was 1.48 and comparable to that achieved by irradiation at 3.0 w. with a log kill 2.85, the combination of rinsing and laser irradiation at 3.0 w resulted in a further significant bacterial reduction as compared to rinsing alone (p = 0.004). irradiation did not result in excessive heat generation at the root surface. carbonization of the root canal wall was observed in single teeth at 3.0 and 4.5 w and no controlled sealing of the dentinal tubules could be achieved in the root canal.
Conclusions:
The application of the diode laser might be an adjunct to conventional endodontic treatment when used in combination with a naocl/h(2)o(2) solution.