Abstract
BACKGROUND: Dental caries is a frequently encountered bacterial oral disease worldwide. Resin-based dental composites (RDCs) are often utilised for restoring dental carious lesions; however, subsequent caries and restoration failure may result from their vulnerability to bacterial colonisation. While adding antibacterial compounds to certain materials may have additional advantages, doing so could also alter their mechanical and physical properties. The current research intended to assess how the addition of the antimicrobial agent cetylpyridinium chloride (CPC) affects the mechanical and physical characteristics of a commercial composite resin. METHODS: In this study, cetylpyridinium chloride (CPC) was incorporated into two commonly used commercial RDCs, namely, the universal Z250XT and the flowable Z350XT, at mass concentrations of 2% and 4%. The hydrolytic stability (water sorption and water solubility) and mechanical properties (flexural strength and flexural modulus) of the samples were subsequently evaluated via ISO 4049 standards after 1, 7, 30, and 90 days of distilled water storage. The samples were also analysed by scanning electron microscopy (SEM) to characterize the filler particle size, shape, and distribution. Quantitative analysis was conducted via three-way ANOVA, and pairwise intergroup and section comparisons were performed via post hoc LSD with Bonferroni correction. The reported p < 0.05 confirmed statistical significance. RESULTS: The flexural strength and modulus slightly decreased with increasing CPC concentration and distilled water storage time. Water sorption and solubility increased with increasing CPC concentration and distilled water storage time. CONCLUSIONS: Overall, the 2% group outperformed the 4% group in terms of mechanical and physical performance. Higher concentrations of CPC in RDCs and prolonged immersion times were linked to decreased flexural properties and increased sorption and solubility. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12903-025-07114-8.