Effectiveness of carbonate removal and demineralization inhibition in primary teeth using a 9.3-μm carbon dioxide...

Studies on permanent dental enamel have shown that irradiation with a 9.3-μm carbon dioxide (CO₂) laser can safely inhibit caries progression in vivo and carieslike lesion formation in vitro. The authors conducted a study to investigate whether 9.3-μm CO₂ laser irradiation could safely inhibit carieslike lesion formation in primary teeth in vitro.

Teeth were irradiated with a 9.3-μm CO₂ laser at a pulse fluence of 0.8 J/cm² and scanned automatically over a target area of 5.8 mm². Two test groups of 15 extracted human molars each were used: (1) laser-irradiated and (2) laser-irradiated plus additional fluoride. Both groups used nonirradiated areas as nonlaser-treated controls. After irradiation, artificial carieslike lesions were generated through a validated pH-cycling protocol. Relative mineral loss (ΔZ) was determined by cross-sectional microhardness testing in depth. Fourier transform infrared spectroscopy was performed on additional 10 irradiated samples to investigate the removal of acid-soluble carbonate groups from the mineral.

Inhibition of carieslike lesion formation relative to untreated enamel was (1) laser-irradiated alone: 56.2%, (2) fluoride alone: 55.0%, (3) laser plus fluoride: 76.5% (significantly different from 1 and 2; P < 0.01). Carbonate removal by laser irradiation (SD) was 50.4% (7.7%) at the surface and detectable to a depth of at least 14 μm.

Irradiation with 9.3-μm CO₂ laser on primary teeth reduced the formation of carieslike lesions and was associated with significant removal of acid-soluble carbonate groups from the enamel mineral. This inhibition was accomplished without an unsafe rise in pulpal temperature and without significant microscopic or visible damage to the enamel surface.