Effect of DPSS Nd: YAG (532 nm) and diode (980 nm) laser treatment on fluoride uptake in dentin following silver diamine fluoride application: An in vitro study

Abstract

Fluoride treatment has long been recognized as an important method for treating dental decay. Silver Diamine Fluoride (SDF) treatment has emerged as a low-cost and simple approach, combining silver’s antimicrobial properties with fluoride’s caries-inhibiting activities. The present study compares the effects of two lasers, diode-pumped solid-state frequency-doubled Nd: YAG (DPSS, 532 nm) and diode (980 nm), on fluoride absorption in dentin when used with SDF. Following treatment with 38% SDF, the prepared dentin specimens were exposed to radiation for 3, 5, and 10 s using either a frequency-doubled Nd: YAG laser (532 nm, 1 W, free-space beam, 3 mm diameter) or a diode laser (980 nm, continuous wave) at 1 W and 3 W power with a 300 μm optical fiber scanned tangentially across the surface at a speed of 1 mm/s. The equivalent energy densities for 1 W and 3 W diode irradiation were approximately 1,414.7 J/cm² and 4,244.1 J/cm², while for Nd: YAG exposure, it ranged from 42.4 to 141.4 J/cm². Evaluation methods included scanning electron microscopy (SEM) to assess dentinal tubule openness and energy-dispersive X-ray (EDX) analysis to quantify fluoride uptake. Statistical analyses included the Kruskal-Wallis test and Mann-Whitney comparisons, with Spearman’s correlation coefficient used to examine relationships between image analysis and EDX results. Results indicated that the combination of SDF treatment with laser irradiation significantly increased fluoride uptake and decreased open dentinal tubules compared to SDF treatment alone (overall P < 0.001). The SDF + diode 3 W group exhibited the highest mean fluoride wt% and the lowest mean% open tubules (significant compared to SDF alone, P < 0.05). The fd-Nd: YAG 10 s group exhibited fluoride levels comparable to diode 3 W. There was a significant negative correlation (ρ = -0.78, P < 0.001) between fluoride wt% and percentage of open tubules. Laser irradiation with Diode at 3 W or fd-Nd: YAG Laser-assisted SDF treatment enhances tubule blockage and boosts surface fluoride retention in a laboratory context. These findings support the use of lasers to optimize the effectiveness of SDF in caries prevention and dentinal tubule sealing. However, more in-vivo and thermal safety research is required before making a clinical recommendation.