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.

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

Objective: To investigate the caries prevention effect of silver diamine fluoride (SDF) with a carbon dioxide (CO2) laser (λ = 10,600 nm) on dentin. Method: Human dentin slices (n = 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 CO2 laser. Group 3 (laser + SDF)-slices were irradiated with a CO2 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. Results: micro-CT determined lesion depths for groups 1-4 were 27 ± 6, 138 ± 32, 17 ± 5, and 182 ± 49 µm, respectively (p < 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 (p = 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 (p < 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. Conclusions: SDF can reduce dentin demineralization against cariogenic challenge, and the caries preventive effect of SDF is further enhanced through CO2 laser irradiation.

Effects of 10,600 nm Carbon Dioxide Laser on Remineralizing Caries: A Literature Review.

Objective: To study the effects of carbon dioxide (CO2) lasers (λ = 10,600 nm) on remineralizing dental caries. Methods: This study involved performing a systematic search of English articles archived in the PubMed, Scopus, and Web of Science databases. The keywords used to identify the relevant articles were ((CO2 laser) OR (carbon dioxide laser)) AND ((dental caries) OR (tooth remineralization)). Publications before 2019 were selected. The titles and abstracts of the initially identified articles were screened. Duplicate records, reviews, and irrelevant studies were removed. Full texts were retrieved for publications that studied the effects of CO2 lasers on remineralizing dental caries. Results: The search identified 543 potentially relevant publications. A total of 285 duplicate records were removed. Sixteen articles were included in this review. Four studies reported that CO2 lasers inhibited bacterial growth. The growth of cariogenic bacteria, mainly Streptococcus mutans, on an irradiated tooth surface was slower compared with nonirradiated ones. Four studies investigated the reduction of the demineralization of enamel with cariogenic challenge. They found that CO2 lasers reduced the carbonate content of mineralized tissues and increased the microhardness of enamel. Nine studies used CO2 lasers associated with topical fluorides in remineralizing dental caries. The results of the synergistic effect of laser irradiation and fluoride application with regard to the inhibition of caries progression varied among these studies, whereas laser irradiation could enhance fluoride uptake to demineralized mineral tissues. Conclusions: CO2 laser irradiation increased acid resistance and facilitated the fluoride uptake of caries-like lesions. In addition, it reduced the growth of cariogenic bacteria.