Laser effects on dentine treated with silver diamine fluoride

Session: Cariology ResearchObjectives: To evaluate the effect of Er:YAG (2,940nm) Laser irradiation and 38% silver diamine fluoride (SDF) application on human sound dentine under cariogenic biofilm challenge. Methods: Six 3mm thick dentine slices were prepared from 6 sound human molars. Each slice was divided into 4 areas for application of distilled water as control (Area 1). Er:YAG Laser (Area 2), SDF (Area 3) and SDF plus Er:YAG Laser (Area 4). The laser irradiation was set at a 100µs pulse and 20Hz repetition rate and applied for 1 sec/mm2. The treated dentine slices were subjected to biofilm challenge, which was formed by five cariogenic bacterias, namely, Actinomyces naeslundii, Lactobacillus acidophilus, Lactobacillus rhamnosus, Streptococcus mutans, Streptococcus sobrinus, in 5% sucrose solution at 37oC for 12 hours. Finally, they were immersed in a buffered remineralizing solution containing calcium chloride and sodium hypophosphate for 12 hours. The surface morphology of the 4 areas of each slice was examined using Scanning Electronic Microscopy. Energy Dispersive X-ray Spectrometery (EDX) was used for elemental analysis. Results: Smooth dentine surface was observed on Areas 1 and 3. A scaly surface with craterlike structures of the dentine surface was observed in Areas 2 and 4. The % weight of fluoride in Areas 1 to 4 were 7.8%, 8.0%, 8.4% and 9.8%, respectively. Area 4 had a higher % weight of fluoride than the other 3 Areas (p=0.029). The Ca/P ratios of Areas 1 to 4 were 1.89, 2.07, 1.92 and 2.40, respectively. The Ca/P ratio in Area 4 was higher than the other 3 Areas (p=0.018). Conclusions: In this laboratory study, SDF application combined with Er:YAG laser irradiation on dentine increased the fluoride content and diminished the demineralization induced by the cariogenic biofilm. This study is supported by HKU Seed Funding Programme for Basic Research #20111115907