Addition-fragmentation chain transfer monomer in dental resins: Synthesis, characterization, and properties

To synthesize an addition-fragmentation chain transfer monomer (AFCTM) and evaluate its effects on the polymerization shrinkage, physical, and mechanical properties of experimental dental resin and composite.

The AFCTM was synthesized using an iodosulfonylation-dehydroiodination process and characterized by FTIR and ¹H NMR spectroscopy. The AFCTM was then incorporated into a dental matrix resin consisting of Bis-GMA, TEGDMA, and photo-initiator system. The degree of conversion (DC%) was measured using FTIR spectroscopy, and polymerization shrinkage kinetics were assessed using the bonded-disk technique. Shrinkage stress was measured with a universal testing machine equipped with a stress measurement device. DMTA analysis was used to determine dynamic mechanical properties. Flexural properties, were evaluated on the photo-polymerized composite samples.

The incorporation of AFCTM into the dental resin system effectively reduced polymerization shrinkage stress. Higher AFCTM concentrations also led to reductions in maximum shrinkage strain and shrinkage strain rates. The incorporation of AFCTM up to 10 % had no statistically significant effect on the flexural properties. Water absorption and solubility increased at higher AFCTM concentrations.

AFCTM demonstrates promise as an additive for dental composites, effectively reducing polymerization shrinkage stress up to 74 %, while maintaining acceptable mechanical properties. Optimization of AFCTM concentration is essential to balance mechanical strength, water absorption, and shrinkage reduction, paving the way for improved dental composite formulations.