Effect of Laser Irradiance and Fluoride Varnish on Demineralization around Dental Composite Restorations

Abstract Introduction: This study aimed to assess the effects of CO۲ and erbium-doped yttrium aluminum garnet (Er:YAG) lasers with and without fluoride varnish on demineralization around composite restorations.Methods: This in vitro experimental study evaluated ۹۶ extracted human premolars. After preparation and restoration of class V cavities in the buccal surface of the teeth with composite resin, they were randomly divided into ۸ groups of control, CO۲ laser (L۱), CO۲ laser-NaF (L۱F), NaF-CO۲ laser (FL۱), Er:YAG laser (L۲), Er:YAG laser-NaF (L۲F), NaF-Er:YAG laser (FL۲) and NaF (F). The entire surface of the teeth, except for the restored cavity in the buccal surface and ۱ mm around the margin, was coated with two layers of nail varnish. The teeth then underwent pH cycling for ۱۰ days (۳ hours in demineralizing solution and ۲۱ hours in remineralizing solution) to artificially induce demineralization. The amount of calcium and phosphorous released into the cariogenic solution was quantified using atomic absorption spectroscopy and spectrophotometry. The Vickers hardness tester was used to measure the hardness of the tooth structure adjacent to composite restoration. Data were analyzed using one-way ANOVA and Tukey’s test.Results: The four groups of L۱F, FL۱, FL۲ and L۲F showed minimum loss of calcium and phosphorous ions, and the mean hardness of FL۱ and FL۲ groups was higher than that of other groups.Conclusion: The CO۲ and Er:YAG lasers alone have no significant effect on the resistance of tooth structure to cariogenic solution. However, they can exert a synergistic effect when used along with NaF varnish. Fluoride varnish applied prior to laser irradiation confers further resistance to the tooth structure and positively affects its hardness. Keywords: Laser Recurrent Caries Fluoride Surface Hardness