Abstract
INTRODUCTION: Caries lesions are high prevalent dental infectious. Gram-positive bacteria are the most common pathogenic microorganisms causing caries lesions. Low-Level laser therapy has been shown to have a significant bactericidal effect without causing damage to the oral tissues. This study was designed to evaluate the efficacy of diode laser (980 nm) at different times and doses on Streptococcus (S.) Mutans and (Lactobacillus) L. Acidophilus microorganisms. METHODS: This study was performed on two groups of microorganisms, including S. mutans and L. acidophilus, at a concentration of 10(8) CFU/ml, which exposed to a diode laser source with a central wavelength of 980 nm to investigate three different energies with the following time-exposures (at doses of 5, 10 and 20 J/cm2 with irradiation times of 5, 10 and 20 s). The growth of bacteria (CFU/ml) was calculated. RESULTS: A significant decrease in CFUs/ml of two microorganisms was observed immediately and 24 h after irradiation (p-value < 0.05). The most effective laser radiation for S. mutans immediately and 24 h after exposure was seen at 5 s with 20 J/cm(2) and 20 s with 5 J/cm(2), respectively. The most effective laser radiation for L. acidophilus was the time of 5 s with 10 J/cm(2) both immediately and 24 h after exposure. CONCLUSION: In the present study, we demonstrated that diode laser (980 nm) has great efficacy in the growth reduction of S. mutans and L. acidophilus at different times and doses.