Chemical and Mechanical Effects of Silver Diamine Fluoride in Dentine

Objectives: To investigate the effect on the chemical structure and the bond strength of sound and demineralized dentin, after the application of two different silver diamine fluoride (SDF) products.
Methods: Thirty-nine human molars were sectioned to expose their dentinal surface, they were randomly divided into 4 experimental groups: (1) sound dentin (2) pH-cycling (3) Cariestop (4) Riva Star. The specimens were subjected to a pH-cycling process for 14 days prior to the application of the products. After the application and sealing of the samples, they were sectioned in 1x1 mm bars. Microtensile bond strength test was evaluated using two adhesives (Clearfil^TMSE BOND 2 and OptiBond^TMFL). Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) was used to evaluate the chemical composition of the dentin. Three spectra of each specimen were performed in each of the time periods studied: immediately, 24h, 48h, 72h, 5d, 7d, 10d and 15d after the application of the product.
Results: Bond strength values were higher in sound dentine with both adhesives. After applying SDF on the dentine submitted to pH-cycling, it dropped significantly regarding the bond strength values, respect to the sound dentin. Cariestop and Riva Star groups, with OptiBond^TMFL, showed bond strength values significantly lowers compared to the pH-cycling group (p=0,001). With Clearfil^TMSE BOND 2, Cariestop maintained its adhesion capacity with respect to pH-cycling, but Riva Star obtained significantly lower values (p<0.001). ATR-FTIR showed an increase in the relative intensity of some peaks between 1000-1600 cm-1 with both SDF.
Conclusions: The use of SDF produces chemical changes in dentine in the short-term. The application of SDF on demineralized dentine decreases immediate the bond strength of dentine adhesives.