A Novel Polyurethane Resin Cement with Dual Caries-prevention Mechanisms Title Page with Author Details

This study aimed to develop a novel polyurethane (PU) resin cement for bonding indirect restorations, incorporating dimethylaminohexadecyl methacrylate (DMAHDM) to address secondary caries. The dual-functional system targeted both prevention of microleakage and bacterial inhibition.

The DMAHDM monomer was synthesized via a modified Menschutkin reaction and incorporated into PU resin cement at mass fractions of 0% to 5%. The cement's properties were evaluated through double bond degree of conversion, water contact angle, polymerization shrinkage, flexural strength, and micro-tensile bond strength. Antibacterial efficacy against Streptococcus mutans, Lactobacillus acidophilus, and Streptococcus gordonii was assessed using early adhesion tests, MTT assays, live/dead biofilm staining, and colony-forming unit (CFU) counts. Biosafety was evaluated via in vitro cytotoxicity and in vivo subcutaneous implantation studies.

The results showed that DMAHDM incorporation up to 3% had minimal impact on mechanical properties. Specifically, the 3% DMAHDM group exhibited a flexural strength of 81.02 MPa and elastic modulus of 3.35 GPa, with significant reductions in flexural strength were observed only at higher concentrations (4%-5%). Polymerization shrinkage increased with DMAHDM content from 2.14% at 0% DMAHDM to 2.95% at 5% DMAHDM. The cement exhibited strong antibacterial activity, with 3%-5% DMAHDM groups achieving 4-5 log₁₀ reductions in bacterial viability. Biosafety assessments indicated acceptable biocompatibility under the in vitro and in vivo conditions tested.

The novel PU resin cement with DMAHDM demonstrated optimal performance at 3% concentration, balancing mechanical properties, polymerization shrinkage, antibacterial efficacy, and biosafety. Further clinical studies are required to confirm its long-term efficacy in preventing secondary caries.

The incorporation of 3% DMAHDM into a polyurethane resin cement provided strong antibacterial activity while maintaining mechanical and interfacial properties comparable to a commercial resin cement under the conditions tested. However, further studies simulating the oral environment and clinical trials are required before claims regarding reduced secondary caries risk or restoration longevity can be made.