Effects of wet environment on physical, chemical and mechanical properties of four core buildup materials

Abstract The physical, chemical and mechanical properties of core buildup materials under wet conditions are critical determinants of their long-term clinical performance. This study systematically evaluates water sorption, solubility, flexural strength, elastic modulus, elution and fracture mode of four commercially available core buildup materials. Twenty disk-shaped specimens were fabricated and immersed in deionized water or artificial saliva for 150 d, followed by a 112-day dehydration period. Parallel specimen sets were incubated for 154 d for extracts analysis. Then flexural strength tests were conducted using a three-point bending testing apparatus at 1, 30, 90 and 150 d, and fractured specimens were subsequently analyzed by scanning electron microscopy. All materials exhibited time-dependent mass variations. SDR demonstrated the lowest water sorption ( P < 0.05), whereas PC exhibited the lowest solubility ( P < 0.05). For elution analysis, urethane dimethacrylate (UMDA) was detected in all specimens during the 1–7 and 28–35 immersion periods. Triethylene glycol dimethacrylate (TEGDMA) was detected during the 1–7 immersion period in all specimens except LC. Besides, NF exhibited the highest flexural strength, while PC demonstrated the highest elastic modulus after 150 d immersion. All tested specimens exhibited a two-part fracture mode, with voids and pores inevitably present. These findings demonstrate that monomer composition predominantly governs the physicochemical stability of core buildup materials, whereas filler characteristics (loading, content, and distribution) dictate their mechanical performance. The results provide critical insights for material selection in clinical applications requiring prolonged exposure to aqueous environments.