# Diffusion of Silver Diamine Fluoride Solution in Dentine: An In Vitro Study

## TL;DR

This study examines how silver and fluoride ions from a solution diffuse through dentine of different thicknesses over 24 weeks.

## Contribution

The study reveals how dentine thickness and tubule characteristics influence the diffusion of silver and fluoride ions from silver diamine fluoride.

## Key findings

- Silver and fluoride ion diffusion through dentine decreased over 24 weeks.
- Thinner dentine allowed more ion diffusion into the pulp.
- Dentinal tubule diameter and number affect ion diffusion dynamics.

## Abstract

The aim of this research was to assess the diffusion dynamics of silver and fluoride ions after 38% silver diamine fluoride (SDF) solution application on dentine of varying thicknesses over 24 weeks.

Bovine dentine discs of 5.5 mm in diameter were prepared and separated into 3 groups with thicknesses of 0.5 mm (group 1), 1.0 mm (group 2), and 1.5 mm (group 3). The diameter and number of dentinal tubules of discs were assessed. Each disc received a topical application of 0.05 mL 38% SDF solution. The deionised water in the tube was collected weekly for 24 weeks. The silver and the fluoride ion concentrations in the collected deionised water were determined. Generalised estimating equations was used to explore the potential effects of the key factors on the silver/fluoride diffusion.

The amount of silver and fluoride ion diffusion through dentine almost levelled off after 4 weeks and showed a decline trend over 24 weeks. The mean (SD) 24-week cumulative ion diffusion through dentine in groups 1, 2, and 3 was as follows: 20 (4) μg, 10 (2) μg, and 5 (1) μg for silver (P < .05) and 18 (2) μg, 13 (2) μg, and 7 (1) μg for fluoride (P < .05), respectively.

Silver and fluoride ion diffusion through dentine showed a decline trend over 24 weeks. The diameter and the number of dentinal tubules on dentine with different thicknesses affects the ion diffusion dynamics. This study provides indications on the pattern of silver/fluoride ions diffusion through dentine to pulp after 38% SDF application. An increased amount of silver/fluoride diffuses through dentine into the pulp with decreased remaining dentine thickness.