Development of 4-META/MMA-TBB resin with added benzalkonium chloride or cetylpyridinium chloride as antimicrobial restorative materials for root caries

To develop antimicrobial restorative materials for root caries, we assessed a 4-META/MMA-TBB resin (Bondfill SB Plus, Sun Medical) containing benzalkonium chloride (BAC) or cetylpyridinium chloride (CPC) at 1.25, 2.5, and 5.0 wt%. The same resin without antibacterial agent was used as control. The degree of conversion was measured by attenuated total reflectance-Fourier transform infrared spectroscopy. The 3-point flexural strength test was conducted according to ISO 4049. The antimicrobial effect against three oral bacteria (Streptococcus mutans, S. sobrinus, and Actinomyces naeslundii) was assessed using agar diffusion tests. The shear bond strength to root dentin was assessed after 24 h of storage in water with or without 10,000 thermal cycles. The shear bond strength data were statistically compared using a linear mixed-effects model (α = 0.05). The specimen with 5.0 wt% BAC showed a significantly higher degree of conversion than the control, but it also had significantly lower flexural strength and lower shear bond strength after thermal cycling than the other specimens. When BAC or CPC was added at ≥ 2.5 wt%, the resins inhibited the growth of the three investigated microbes. In conclusion, both BAC and CPC showed significant antimicrobial effects when added at 5.0 wt% to the 4-META/MMA-TBB resin. Up to 2.5 wt%, neither antimicrobial agent affected the degree of conversion, flexural strength, or shear bond strength of the resin.