Bactericidal effect of pulsed 1,064 nm Nd : YAG laser light on Staphylococcus epidermidis is of photothermal origin: An in vitro study

Background and Objective: The aim was to investigate the bactericidal effec t of the 1,064 nm Nd:YAG laser on Staphylococcus epidermidis. Material and Methods: S. epidermidis was inoculated on agar plates and then exposed to pulsed laser light in three different modes: with an uninterrup ted train of pulses, or with two different repeated cycles of fractionated trains of pulses. The agar temperature was measured directly after uninterr upted radiation. Results: A bacterial growth inhibition area of 0.3 cm(2) and maximum temper ature of approximately 80 degreesC was observed after uninterrupted radiati on at 2,000 J cm(-2). The corresponding figures after an exposure of 5,000 J cm(-2) were 0.9 cm(2) and 100 degreesC, respectively. No bacterial inhibi tion was observed after exposure to repeated cycles of 20 seconds of radiat ion followed by 60 seconds of rest. Conclusion: The antimicrobial effect of the 1,064 nm Nd:YAG laser light is caused by a photothermal rather than a photochemical effect. (C) 2000 Wiley -Liss, Inc.