The Inhibitory Effect of CW CO2 Laser on Carieslike Lesion Initiation on Sound Enamel: an In Vitro Study

Although CO2 laser irradiation can decrease enamel demineralization, it has still not been clarified which laser wavelength and which irradiation conditions represent the optimum parameters for application as preventive treatment. One of the important applications of the laser is as a caries inhibition treatment of the sound dental tissues. This study aimed to assess the caries preventive potential of various CW CO2 laser parameters, and to explore the effect of laser power density, and the exposure time on the caries inhibition activity. Eighty one extracted human premolar teeth were irradiated with three output power: (1, 2, and 4) W, three spot diameter: (2, 2.83, and 4) mm, and three exposure times: (0.2, 0.4, and 0.8) sec of 10.6µm CW CO2 laser. Three teeth were used as a control group. All teeth were subjected to carieslike lesion formation by 3.5 pH lactic acid solution for 21 days. The teeth after that were sectioned into ground cross sections and the lesion depths were measured under polarizing microscope. The lesion depths of experimental samples were compared with those of the control samples. A single exposure to CW CO2 las er irradiation was found to be resulted in reduction of the carieslik e lesion depths. These reductions were up to 61%. The inhibition activity was related directly to the power density and inversely to the exposure time of CW CO2 laser radiation. The optimal parameters were 33W/cm2 power density and 0.2 exposure time. These finding should be reinforced with more laboratory, animal, and human studies with and without fluoride before clinical applications.