Effect of 532 nm and 671 nm Diode Lasers Irradiation on Calcium Solubility in Human Dental Enamel: An Ex-Vivo Study

Aim: This study aimed to measure the amount of calcium dissolved from dental enamel of extracted human teeth immersed in lactic acid solution after irradiation by 532 nm (100 mW) and 671 nm (100 mW) continuous wave diode lasers.
Methodology: One hundred and forty freshly extracted human premolar teeth were used. Samples were prepared by cutting each tooth into two cubic specimens of 4x4 mm enamel surface (one for irradiation and the other as control).The surfaces of the cube were coated by acid resistant varnish leaving the 4x4 enamel on one surface uncovered. Irradiation was done for each wavelength with 4, 8, 12 and 16 minute intervals. The control and the irradiated specimens were immersed in 3 ml lactic acid (pH 4.4) for 24 hours under a temperature of 37°C. The amount of calcium dissolved was measured by an atomic absorption spectrophotometer. Comparison between variables was done by ANOVA and Chi-square tests with the level of significance set at p ≤ 0.05.
Results: The findings of this study showed that the percentages of calcium dissolved in the laser groups were less. Eight minutes irradiation time revealed the highest percentages of teeth with less calcium content (for 671 nm diode laser–81.25% and for 532 nm–78.60 %).The mean of calcium dissolved in acid decreased with increasing the irradiation time with P values of 0.013 and 0.000 for 532 nm and 671 nm, respectively.
Conclusion: Low power diode laser S of wavelengths 532 nm and 671 nm showed a decrease in calcium solubility in comparison to the control group; so it is a promising result in caries prevention. By increasing irradiation time, to a certain value, resistance to acid dissolution also increases.