38% silver diamine fluoride for dentine hypersensitivity treatment: an in situ study

Silver diamine fluoride (SDF) is a desensitizing agent approved by the U.S. Food and Drug Administration. However, limited evidence is available to guide the optimal application protocol for SDF. This in situ study aimed to compare dentinal tubule occlusion scores and examine the elemental composition of occluding materials after single versus weekly applications of 38% SDF over 2 weeks.

Five healthy participants took part in this in situ study, which included three 14-day experimental periods and a 7-day washout between periods. In the first experimental period, distilled water (DI) was applied on Day 1. In the second experimental period, SDF was applied once on Day 1. In the third experimental period, SDF was applied on Days 1 and 8. Each participant wore an intraoral palatal appliance containing four treated dentine blocks during the experimental periods. The dentine blocks were removed from the participants' mouths and exposed extraorally to citric acid (pH 3.2) for 2 min, five times daily, for 14 days. Dentinal tubule occlusion scores and the elemental composition of the occluding materials were evaluated using scanning electron microscopy (SEM) images and energy-dispersive x-ray spectroscopy (EDS), respectively. Dentinal tubule occlusion scores were analyzed using one-way analysis of variance (ANOVA) followed by Tukey's HSD post hoc test, whereas EDS elemental composition data were analyzed using the Kruskal-Wallis test followed by Dunn's post hoc test with Bonferroni correction.

All five participants completed all three experimental periods. The mean dentinal tubule occlusion scores were 1.80 ± 0.35 for the DI group, 3.29 ± 0.27 for the single-application SDF group, and 4.10 ± 0.10 for the weekly-application SDF group (DI < single-application SDF < weekly-application SDF; p < 0.001). EDS analysis of dentine blocks revealed a silver peak in both SDF groups, with a higher silver weight percentage in the weekly-application SDF group than in the single-application SDF and DI groups (DI < single-application SDF < weekly-application SDF; p < 0.001).

Although not without limitations, this study reveals that a weekly protocol results in superior dentinal tubule occlusion scores compared to a single application, and that increased frequency of SDF application directly contributes to a higher weight percentage of silver in the resulting occluding materials.