Development of antibacterial dual-cure dental resin composites via tetrapod-shaped zinc oxide incorporation.

Objectives: This study aimed to evaluate the effects of incorporating the 0-20 wt% tetrapod-shaped zinc oxide (tZnO) whiskers on the mechanical, antibacterial, and cytotoxic properties exhibited by experimental dual-cure resin composites.

Methods: Commercially obtained tZnO whiskers underwent surface modification using 3-methacryloxypropyltrimethoxysilane (γ-MPS). Subsequently, four groups of resin composites containing 0, 5, 10, and 20 wt% silanized tZnO along with barium borosilicate glass (BaBSG) fillers were fabricated while maintaining total filler loading at 60 wt%. Mechanical properties were examined utilizing specimens produced adhering to ISO 4049:2019 guidelines where applicable. Depth of cure was quantified immediately, while three-point flexural strength, flexural modulus, fracture toughness, Vickers hardness, compressive strength, and diametral tensile strength were assessed after 24 h of storage in 37 °C distilled water. Planktonic bacteria of Streptococcus mutans (S. mutans) were cultured and tested for antibacterial activity using disk diffusion and microbial anti-adhesion assays. Cytotoxicity was examined by preparing extracts from specimens in a cell culture medium and exposing stem cells from human exfoliated deciduous teeth (SHED) to serial dilutions of these extracts, then assessing cell viability and survival using CCK-8 assay and live/dead staining.

Results: Elevating tZnO loading yielded significant reductions in depth of cure, compressive (from 296.4 to 254.6 MPa), and diametral tensile strength (from 42.7 to 31.0 MPa), while flexural strength (91.3-94.1 MPa), flexural modulus (6.4-6.6 GPa), fracture toughness (0.96-1.04 MPa·m), and Vickers hardness (36.5-37.4 kgf·mm) remained the same. Composites integrating tZnO displayed markedly enhanced antibacterial activity against S. mutans, based on anti-adhesion tests and live/dead staining. No cytotoxicity was observed for SHED treated with extracts from resin composites possessing up to 20 wt% tZnO whiskers.

Significance: This study demonstrates that incorporating up to 20 wt% silanized tZnO in place of traditional barium glass particles appreciably enhances dual-cure resin composite antibacterial function against S. mutans without compromising mechanical properties.