Secondary caries is the primary cause
of composite restoration
failures, resulting from marginal leakage and bacterial accumulation
in the oral environment. Antibacterial dental composites, especially
antibacterial monomers, have emerged as a promising strategy to inhibit
secondary caries, which is pivotal to prolonging the lifespan of dental
restorations. In this work, monomethacrylate- and dimethacrylate-functionalized
betulin derivatives (M1Bet and M2Bet) were synthesized
via an esterification reaction and served as antibacterial comonomers
to develop novel dental resin formulations, in which M1Bet and M2Bet were incorporated to partially or completely
replace bisphenol A glycerolate dimethacrylate (Bis-GMA). The control
resin was a mixture based on Bis-GMA and tri(ethyleneglycol) dimethacrylate
(TEGDMA) with a weight ratio of 50:50 (5B5T). The effect of the resin
compositions and the chemical structures of M1Bet and M2Bet on the rheology behavior, optical property, polymerization
kinetics, mechanical performance, cell viability, and antibacterial
activity of dental resins were systematically investigated. Among
all materials, the 1M2Bet4B5T resin with 10 wt % substitution
of Bis-GMA by M2Bet exhibited comparable viscosity, higher
light transmittance, improved degree of conversion, and mechanical
properties compared with 5B5T. After incubation for 24 h, this optimal
resin also possessed the best antibacterial activity against Streptococcus mutans, which had a significantly lower
bacterial concentration (1.53 × 109 CFU/mL) than 5B5T
(9.03 × 109 CFU/mL). Introducing betulin-based comonomers
into dental resins is a potential strategy to develop antibacterial
dental materials without sacrificing physical–mechanical properties.