Effect of diode laser irradiation on the survival rate of gingival fibroblast cell cultures

Background and Objective: The present study is part of a basic research pro gram investigating the cellular effects of the GaAlAs-diode laser with a wa velength of 810 nm on human periodontal tissues. The aim of the investigati on was to evaluate the effects of the laser treatment an the survival rate of human gingival fibroblasts (HGF) in monolayer cell culture at different power settings and durations. Study Design/Materials and Methods: HGF were obtained from a human gingival connective tissue explant. Cells were cultured on 24-well tissue culture p lates. One hundred and thirty multi well cell cultures were laser treated. The variable parameters were power output (0.5-2.5 W) and exposure time (60 -240 seconds per well). The cultures were analyzed by means of trypan blue staining, and the cell numbers counted under a light microscope. Photograph s before and after irradiation were taken and evaluated. Results: Depending on different settings, the laser irradiation caused sign ificant (P < 0.05, t-test) reductions of cell numbers. Exposure time was mo re relevant to this phenomenon than the power output. Linear regression ana lysis revealed no unambiguous correlation between power output and cell dea th, when exposure time was kept constant. Conclusion: When used for periodontal pocket decontamination, the laser bea m may cause damage to collateral periodontal tissues, if the power setting and the duration of the treatment are not adequate. Further investigation, especially with regard to the effects on hard tissue and microorganisms, ar e needed to give a secure recommendation for irradiation parameters at pock et decontamination. (C) 2001Wiley-Liss, Inc.