Antibacterial response of oral microcosm biofilm to nano-zinc oxide in adhesive resin

Objective. Various nanoparticles are currently under investigation to impart biointeractivity for dental materials. This study aimed to: (1) formulate an experimental dental adhesive containing ZnO nanoparticles; (2) evaluate its chemical and mechanical properties; and (3) assess the antibacterial response against oral microcosm biofilm. Methods. Nanosized ZnO was chemically and morphologically evaluated. ZnO was incorporated at 0 (G(CTRL)), 2.5 (G(2 5%)), 5 (G(5)(%)) and 7.5 (G(5)(%)) wt.% in an experimental dental adhesive. The adhesives were evaluated for the degree of conversion (DC), flexural strength (FS), and elastic modulus (E). The antibacterial activity was evaluated using a 48 h-microcosm biofilm model after the formation of acquired pellicle on samples' surfaces. Colony-forming units (CFU), metabolic activity, and live/dead staining were assessed. Results. Nanosized ZnO presented characteristic peaks of Zn-O bonds, and the particles were arranged in agglomerates. The DC ranged from 62.21 (+/- 1.05) % for G(Ctrl) to 46.15 (+/- 1.23) % for G(7)(.5%) (p <0.05). G(7)(.5%) showed lower FS compared to all groups (p <0.05). Despite achieving higher E (p < 0.05), G(2)(.5%) did not show differences for G a n regarding the FS (p >0.05). G(7)(.5%) had lower CFU/mL compared to G ail for mutans streptococci (p < 0.05) and total microorganisms (p <0.05), besides presenting lower metabolic activity (p <0.05) and higher dead bacteria via biofilm staining. Significance. The dental adhesives' physicochemical properties were similar to commercial adhesives and in compliance with ISO recommendations. G(7)(.5%) restricted the growth of oral microcosm biofilm without impairing the physicochemical performance. (C) 2020 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Automated summary

This study formulated and evaluated an experimental dental adhesive containing ZnO nanoparticles, assessing its chemical and mechanical properties, as well as its antibacterial response against oral microcosm biofilm. The results showed that the dental adhesive with 7.5% ZnO effectively restricted the growth of oral microcosm biofilm.