The role of silver diamine fluoride in resin bonding to eroded dentin: A six-year in vitro evaluation.

PURPOSE: To evaluate whether different concentrations of silver diamine fluoride (SDF) influence the resin-dentin bond strength of two universal adhesives after six years of aging.

METHODS

A total of 160 sound human molars were used and allocated into 20 experimental groups. Of these, 128 teeth were subjected to an erosive pH-cycling model and randomly distributed into 16 experimental groups (n = 8 teeth/group) according to: (1) SDF treatment (no treatment, 12 % SDF, 38 % SDF, or 38 % SDF combined with potassium iodide [38 % SDF+KI]); (2) adhesive system (Scotchbond Universal, Solventum [SBU], or Clearfil Universal Bond Quick, Kuraray [CUQ]); and (3) application mode (etch-and-rinse [ER] or self-etch [SE]). The remaining 32 sound molars were assigned to four additional control groups consisting of untreated sound dentin (n = 8 teeth/group). Restorations were performed, and the specimens were sectioned into resin-dentin bonded beams. Specimens obtained from the same tooth were randomly assigned by random sampling to testing the factor time (24 h or after 6 years of water storage), ensuring a balanced design with respect to tooth dependency. Microtensile bond strength (µTBS) testing and scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM/EDX) analyses were conducted. Data were analyzed using multifactorial ANOVA and Tukey's post hoc test (α = 0.05).

RESULTS

At 24 h, untreated eroded dentin exhibited significantly lower µTBS values than sound dentin (p < 0.05). Pretreatment with SDF (12 %, 38 %, or 38 %+KI) significantly increased µTBS in eroded dentin (p < 0.05), with no significant differences among SDF concentrations or application modes (p > 0.05). After six years of aging, µTBS values significantly decreased in all groups (p < 0.05), with the greatest reduction observed in untreated eroded dentin. SDF pretreatment reduced bond degradation over time, and 38 % SDF resulted in the highest µTBS values (p < 0.05), surpassing those of untreated sound dentin after aging (p < 0.05). SEM-EDX analysis revealed silver-rich deposits at the resin-dentin interface in SDF-treated groups, as well as higher calcium and phosphorus signals after aging, indicating enhanced mineral stability.

SIGNIFICANCE: SDF enhances both immediate and long-term resin-dentin bond durability in eroded dentin in a concentration-dependent manner, irrespective of adhesive type or application mode. However, the adjunctive use of potassium iodide may reduce these beneficial effects.