Dentin Bond Strength of Resin Cements Under Simulated Intraoral Humidity Conditions

BACKGROUND/AIMS: Adhesive procedures performed after dental trauma are often carried out in emergency settings with compromised isolation due to bleeding, limited access, and patient cooperation. This study evaluated how variation in intraoral relative humidity influences dentin bond strength of three resin cements under simulated intraoral temperature. METHODS: A methyl methacrylate-based self-curing resin cement (Super-Bond EX), a primer-assisted dual-cure resin cement (Panavia V5), and a self-adhesive dual-cure resin cement (SA Luting Multi) were tested at 50%, 65%, 80%, and 95% relative humidity at 32°C. Mid-coronal bovine dentin was prepared and resin composite rods were bonded in a humidity-controlled environmental chamber according to the manufacturers' instructions, following an ISO/TS 16506:2017 Annex A of the ISO standard-based shear bond strength framework. For the primer-assisted cement, the primer was applied outside the chamber under ambient conditions to standardize solvent evaporation, and specimens were then transferred into the chamber for cementation. Shear bond strength was measured after 24 h water storage at 37°C, and failures were classified as interfacial or cohesive. RESULTS: The methyl methacrylate-based cement showed stable bond strength across all humidity conditions with no significant differences among groups. The primer-assisted cement demonstrated significantly higher bond strength at 50% relative humidity than at 65%, 80%, and 95% (p < 0.05) and showed predominantly interfacial failures at and above 65% relative humidity. The self-adhesive cement showed the lowest bond strength overall, with mainly interfacial failures and only minor changes across humidity levels. CONCLUSIONS: Under simulated intraoral conditions, dentin bonding performance depended mainly on cement type. The methyl methacrylate-based cement maintained stable bond strength even at high humidity, whereas the primer-assisted cement was more susceptible at and above approximately 65% relative humidity. The self-adhesive cement showed consistently low bond strength irrespective of humidity.