The effect of novel solvent formula of primer containing functional monomer on improving the durability of dentin adhesion

OBJECTIVE: The study was designed to investigate how varying ratios of a functional monomer, 4-formylphenyl acrylate (FA) primer, formulated with a blend of ethyl-acetate (EAC) and ethanol (ET), impact the adhesive durability of All Bond Universal (ABU) and Single Bond Universal (SBU) under both etching and rinsing modes. METHODS: FA was synthesized via the acyl chloride reaction. FA primer was prepared by mixing ethyl acetate and ethanol as a binary solvent system at solvent ratios of 7:3, 6:4, 5:5, and 4:6. The optimal ratio of ethyl acetate to ethanol was determined by measuring the degree of conversion (DC) and contact angle, combining the microtensile bond strength (µTBS) and fracture pattern immediately and 10,000 thermocycles. Matrix metalloproteinases (MMPs) activities and adhesive infiltration at the interface were observed, whereas scanning electron microscopy was used to further evaluate nanoleakage and resin rags. RESULTS: Application of the primer containing a mixed EAC:ET-4:6 solvent resulted in a significant enhancement in the µTBS of both immediate and aging groups, and the contact angle of the demineralized dentin surface. Confocal Laser Scanning Microscope (CLSM) and Scanning Electron Microscope (SEM) were further observed the infiltration properties of resin rags in the bonding interface were strengthened. The MMPs activities in the hybrid layer was clearly inhibited, and the degree of nanoleakage at the bonding interface reduced remarkably, thus, it improved the stability and durability of the bond. CONCLUSION: FA primers containing appropriate ratios of ethanol and ethyl acetate solvents can simplify operation procedures, enhances collagen fiber resistance to enzymatic degradation, and improves hybrid layer sealing, thereby increasing bonding strength. CLINICAL SIGNIFICANCE: The FA primer formulated with an ethyl acetate-ethanol mixed solvent aim to achieve high-strength, low leakage, and long-term durable adhesive effects, demonstrating dual functional advantages: Effective collagen crosslinking capacity leading to enhanced bond durability and reduced secondary caries incidence, alongside decreased technique sensitivity. These findings provide novel perspectives for FA primer applications in clinical practice.