Antibacterial Activity and Caries Prevention of Silver Diamine Fluoride on Irradiated Root Dentin: Effects of Application Time and Light Curing

Objectives To evaluate the caries-preventive effects of silver diamine fluoride (SDF) applied using different protocols on root dentin by assessing antibacterial activity and carious lesion prevention in nonirradiated (NR) and irradiated (IR) dentin. Materials and methods Two hundred and forty root dentin specimens were allocated into eight groups based on dentin substrate (NR or IR) and SDF application protocol: control, 10 s application (10s), 10 s application with light curing (10sLC), and 60 s application (60s). Silver and fluoride distribution from the surface to a depth of 500 μm was analysed using energy-dispersive X-ray spectroscopy ( n = 10). A multispecies biofilm model was used to evaluate biofilm biovolume and bacterial viability after 24 hours ( n = 10). Carious lesion depth was assessed after 10 days of biofilm challenge ( n = 10). Three-way ANOVA was applied for elemental analysis, while two-way ANOVA was used for biofilm analysis and lesion depth. Results The 10sLC and 60s application groups demonstrated superior surface silver precipitation, with greater accumulation observed in IR dentin. All SDF-treated groups showed significant suppression of biofilm formation and reduced bacterial viability compared with controls. Lesion depth was greater in IR dentin than in NR dentin. The greatest lesion depth reduction occurred in NR10sLC (NR dentin) and in IR10sLC and IR60s groups (IR dentin). Conclusions SDF effectively prevented caries in both dentin substrates, while IR dentin was more susceptible to lesion formation. The 10sLC protocol reduced lesion depth more than 60s in NR dentin, with comparable efficacy in IR dentin.