Effect of CO₂ Laser and Fluoride Varnish on Permanent Enamel

Fluoride is widely used to prevent dental caries. CO₂ laser irradiation can increase enamel resistance to demineralization. The synergistic effect of fluoride and CO₂ laser irradiation on the inhibition of dental caries is not clear. Objective: The aim of the present in vitro study was to evaluate the effect of fluoride varnish and CO₂ laser treatment, alone and in combination, on permanent tooth enamel properties. Methods: Caries-free human third molars were divided into five segments and each segment was assigned to one of five groups: (1) control (C), (2) fluoride varnish (F), (3) CO₂ laser irradiation (L), (4) fluoride varnish followed by CO₂ laser irradiation (FL), and (5) CO₂ laser irradiation followed by fluoride varnish (LF). To determine crystallographic change X-ray diffractometer (XRD) was performed. Enamel surface microhardness was analysed using the microhardness tester. Artificial caries-like lesions were created and the lesion depth was measured. Results: XRD analyses showed that there was more fluorapatite in FL compared to any other groups. No significant difference in Vicker's hardness number among C, L, FL, and LF was found (p>0.05). A significant decrease of the lesion depth was found in F/FL/LF compared with the control (p<0.01). Comparison of the lesion depth among the treatment groups of F, FL, and LF showed no statistical difference (p>0.05). Conclusion: Overall, the present data suggested that the combined treatment of fluoride and CO₂ laser irradiation and fluoride varnish only have a similar inhibitory effect on caries-like formation.