Effects of Proanthocyanidin-Functionalized Hydroxyapatite Nanoparticles on Dentin Bonding.

Objectives: To evaluate the effect of proanthocyanidin-functionalized hydroxyapatite nanoparticles (nHAp_PA) used at different concentrations as therapeutic primer on the microtensile bond strength (µTBS) and endogenous enzymatic activity of a universal adhesive to dentin.
Methods: Human sound dentin blocks were randomly allocated into five groups (n=10): i) no treatment (negative control); ii) 14 days of pH-cycling (positive control); iii) pH-cycling + nHAp_PA 2% for 60s; iv) pH-cycling + nHAp_PA 6.5% applied for 60s; v) pH-cycling + nHAp_PA 15% applied for 60s. A self-etch adhesive (Clearfil Se Bond 2, Kuraray) was used for bonding procedures before resin composite build-ups (Brilliant Ever Glow, Coltene). Specimens were tested with the µTBS test after 24h (n=20) and 6 months (n=20) of laboratory storage. The proteolytic activity in each group was evaluated with gelatin zymography. Data were statistically analyzed (p<0.05).
Results: At 24h all treated samples had significantly higher µTBS than controls (p<0.05), with no differences between them. Artificial aging significantly decreased the bond strength in all groups; however, experimental groups still yielded higher bonding values than the control groups (p<0.05). In addition, the negative control had the lowest while nHAp_PA 2% and nHAp_PA 15% the highest bond strengths (p<0.05). Gelatin zymography showed that the groups pre-treated with nHAp_PA exhibited less MMP-9 and MMP-2 activities, in their pro and active forms, than the positive control group, irrespective of the concentrations.
Conclusions: Dentin pretreatment with nHAp_PA prior bonding procedures increased the bonding performances of a self-etch adhesive and inhibited MMP-2 and MMP-9 activities after 6 months.