Development of Rapidly Polymerizing Monomethacrylates as Reactive Diluents

Objective: Reactive diluents such as TEGMDA have been widely used with Bis-GMA or UDMA to achieve photo-curable resins with appropriate viscosity and higher reactivity. However, some significant drawbacks in these materials, such as unreacted monomer and polymerization shrinkage, still exist. The aim of this work is to investigate whether the cure and material properties can be improved in dental resins containing novel monomethacrylates as reactive diluents so that these Bis-GMA-based copolymers have reduced polymerization shrinkage but higher overall double bond conversion. Methods: Several examples of ultra-high-reactivity monomethacrylates that contain secondary functionalities have been synthesized and investigated. With TEGDMA/Bis-GMA (30:70 mass ratio) and 0.1wt% UV initiator DMPA as control, various monomers were mixed with Bis-GMA in the same ratio, and the monomer mixtures were polymerized to maximum conversion under identical cure conditions. The polymerization rate and double bond conversion were monitored using photo-FTIR. Polymerization shrinkage was measured using ACTA linometer. Results: Compared with the TEGDMA/Bis-GMA system, all the monomethacrylate/Bis-GMA systems studied showed higher final conversions, faster curing rates, and decreased polymerization shrinkage. Compared with the TEGDMA/Bis-GMA control, our optimum mixture achieved 86% final conversion (vs. 65%), a polymerization rate 3.5 times faster and an 11% reduction in polymerization shrinkage. Conclusions: These results indicate that certain highly reactive, novel monomethacrylates possess very promising potential to replace TEGDMA as reactive diluents and can readily be applied to develop superior dental resins. (Supported by NIH grant# DE10959 and IUCRC-Fundamentals and Applications of Photopolymers)