Antibacterial effect and micotensile bond strength of a dentin bonding agent with silver nanoparticles biosynthesised with red propolis from Algoas

The antibacterial action of adhesive systems is an important property, since viable bacteria can remain after the preparation of the cavity. Red propolis is a natural product with antimicrobial and antioxidant activities. The biological synthesis of nanoparticles stands out for being ecologically correct, economical and for reducing toxicity. The aim of this study was to evaluate the conversion degree, antimicrobial activity and bond strength of an experimental dentin bonding agent with silver nanoparticles biosynthesized with red propolis (NPAgB) and silver nanoparticles obtained by conventional synthesis (NPAgC). Two experimental adhesives were synthesized with 250 µg / mL of NPAgB and NPAgC. The pure experimental adhesive and Single Bond 2 (3M / ESPE) were used as controls. Measurements of the conversion degree (CD) of the adhesives were obtained from FTIR spectra. The antioxidant (AA) and antimicrobial activities of NPAgB and NPAgC were evaluated, respectively, by the DPPH method and against S. mutans, S. aureus, S. epidermidis, E. faecalis. Disk diffusion metod (DMM) was used to check the antimicrobial activity of the polymerized adhesives. Microtensile bond strength (µTBS) of the adhesive / dentin interface was measured 24h after restoration. GC of the tested adhesives varied between 76.19 and 87.57% (p <0.05). NPAgB showed better AA% (60%) than NPAgC (52%). The results showed that, compared to NPAgC, NPAgB showed better bacteriostatic activity, except against E. faecalis, a group that showed similar results for both types of nanoparticles. In the DMM test, the NPAgB adhesive provided a diffusion radius of 3.7mm. There was no statistically significant difference (p> 0.05) between the µTBS of adhesives with NPAgB (39.56 MPa), NPAgC (36.17 MPa) and the control group (34.88 MPa). The experimental adhesive with NPAgB showed good antimicrobial activity, adequate conversion degree and bond strength.