Objectives: To evaluate the incorporation of doxycycline (DOX) into a commercial dental adhesive regarding physicochemical properties, microtensile bond strength (μTBS), nanoleakage (NL), nanohardness (NH) and Young's modulus (YM), metalloproteinases (MMP) inhibition, and antibiofilm activity.
Methods: DOX was incorporated into the adhesive at 0.05, 0.1, 0.5, and 1 wt%. Restored teeth were evaluated for μTBS, NL, NH, and YM after 24 -hs and 1-year of water storage. Biofilms of Streptococcus mutans were grown on top of these adhesives and determined for bacterial viability and amount of biomass. The inhibitory effect on MMP was analyzed by in situ zymography under confocal microscopy.
Results: Adhesives with 0.5 and 1 wt% of DOX presented reduced pH and degree of conversion. The incorporation of DOX did not affect μTBS and hybrid layer YM. The control group (no DOX) had a decrease in μTBS and the densest silver nitrate areas after 1-year storage. Hybrid layer NH values increased with 0.1 wt% DOX compared to control and 1 wt% DOX groups, at 24 -hs. After 1-year storage, NH of 1 wt% DOX adhesive decreased compared to the control group. The 0.5 and 1 wt% concentrations of DOX decreased the bacterial viability and the biofilm biomass. Confocal images suggest an increased MMP inhibition proportional to the percentage of DOX.
Conclusion: At any concentration, DOX-doped dental adhesives were able to inhibit MMP activity, diminish nanoleakage, and maintain the resin-dentin bond-strength after 1 year of artificial aging.
Clinical significance: Doxycycline-doped dental adhesive inhibited metalloproteinases activity and preserved interface bond strength. This formulation has a potential to improve adhesive restorations clinical longevity.
Keywords: Adhesion; Collagen; Degradation; Dentin.
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