Evaluation of the effectiveness of low power diode laser with different wavelengths in dental caries prevention

Objectives: To investigate the effectiveness of low power diode lasers, with different wavelengths and different irradiation times in caries prevention an ex vivo study. Materials and Methods: True experimental posttest design on 130 extracted human premolar teeth by measuring caries-like lesions examined by polarized light electron microscope after irradiation by four low power diode lasers 532 nm (4 mW), 671 nm (100 mW), 675 nm (30 mW), and 810 nm (20 mW). A fifth group was added as a control (without irradiation). The specimens were prepared by coating the teeth with acid resistance nail varnish leaving uncovered 2 mm × 2 mm of the enamel surface mesially or distally below the contact area. For each wavelength, samples were divided into three groups for three irradiation time as 4, 8, and 12 min; each group consisted of 10 teeth. Irradiated samples and the control were immersed in lactic acid (4.8 pH) and incubated for 21 days under controlled temperature of 37°C and controlled PH of 4.8. After the incubation period, the teeth were sectioned longitudinally by dissecting the 2 × 2 enamel window and the depth of the lesion was measured microscopically. ANOVA test was used to compare between different wavelengths and different irradiation times with level of significant set at P ≤ 0.05. Results: The depth of the caries-like lesions in 810 nm and 675 nm was more than that in control group (180 μm), while statistical significant difference was found (P = 0.002); when the 671 nm and 532 nm lasers wavelengths revealed depth of 70 μm and 112 μm, respectively. Increasing irradiation time decreases the depth of caries-like lesions. Conclusion: Diode laser of wavelengths 532nm and 671 nm showed less depth than control group, indicating caries prevention effect. Increasing irradiation time to a certain value increases resistance to acid dissolution.