Preventing Enamel Caries Using Carbon Dioxide Laser and Silver Diamine Fluoride.

Objective: This study was intended to investigate the caries prevention potential of carbon dioxide (CO2) laser (λ = 10,600 nm) irradiation followed by application of silver diamine fluoride (SDF) to enamel. Materials and methods: Human enamel specimens were randomly allocated to four groups (n = 10 per group). Group 1 specimens were treated with SDF; Group 2 specimens were treated with a CO2 laser; Group 3 specimens were irradiated with a CO2 laser then treated with SDF, and Group 4 specimens received no treatment. All specimens were subjected to pH cycling for cariogenic challenge. Lesion depth, microhardness, surface morphology, and elemental analysis were assessed. Results: The lesion depths for Groups 1-4 were 33 ± 16, 80 ± 9, 18 ± 15, and 102 ± 9 µm, respectively (p < 0.001; Group 3 < Group 1 < Group 2 < Group 4). Knoop hardness values for Groups 1-4 were 61 ± 19, 68 ± 20, 78 ± 27, and 36 ± 8, respectively (p = 0.002; Group 4 < Groups 1, 2, and 3). The enamel in Group 4 but not in the other groups showed a roughened surface resembling an acid-etched pattern. Calcium-to-phosphorus molar ratios of Groups 1-4 were 1.68 ± 60.09, 1.61 ± 0.06, 1.69 ± 0.10, and 1.49 ± 0.10, respectively (p < 0.001; Group 4 < Groups 1, 2, and 3). Conclusions: Using the CO2 laser or SDF separately enhanced the resistance of enamel to cariogenic challenge. Moreover, there was an additional effect of the combined use of the CO2 laser and SDF for preventing enamel demineralization.