Caries Prevention Effects of Silver Diamine Fluoride with 10,600 nm Carbon Dioxide Laser Irradiation on Dentin.

To investigate the caries prevention effect of silver diamine fluoride (SDF) with a carbon dioxide (CO) laser (λ = 10,600 nm) on dentin. Human dentin slices ( = 10) were prepared and allocated to the following treatments: Group 1 (SDF)-slices received an SDF application. Group 2 (laser)-slices were irradiated with a CO laser. Group 3 (laser + SDF)-slices were irradiated with a CO laser, followed by an SDF application. Group 4 (negative control)-slices had no treatment. All of the slices were subjected to pH cycling for cariogenic challenge. Lesion depth, nanohardness, and chemical and morphological changes were assessed by microcomputed tomography (micro-CT), nanoindentation, and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), respectively. micro-CT determined lesion depths for groups 1-4 were 27 ± 6, 138 ± 32, 17 ± 5, and 182 ± 49 μm, respectively ( < 0.001; group 3 < group 1 < groups 2 and 4). The nanohardness values for groups 1-4 were 456 ± 109, 288 ± 5, 444 ± 142, and 258 ± 76 MPa, respectively ( = 0.003; groups 2 and 4 < groups 1 and 3). EDS determined that the calcium-to-phosphorus molar ratio for groups 1-4 were 1.26 ± 0.12, 1.07 ± 0.19, 1.37 ± 0.08, and 0.80 ± 0.17, respectively ( < 0.001; group 4 < group 2 < groups 1 and 3). SEM evidenced no ablation or cracking on the lased dentin surfaces. The treated dentin showed a relatively more intact and smoother surface morphology compared with the untreated dentin. SDF can reduce dentin demineralization against cariogenic challenge, and the caries preventive effect of SDF is further enhanced through CO laser irradiation.