RESIN CURE DETERMINATION BY POLYMERIZATION SHRINKAGE

Objectives. This study was designed to develop a methodology that woul d measure the monomer conversion of dental restorative resins without the use of an infrared spectrometer. Methods. Specimens were prepared from heat-cured TEGDMA/MMA copolymers consisting of 0,20,40,60, 80 and 100 mole% TEGDMA. The pre- and post-cure volumes of bar-shaped specim ens (45 x 7 x 1 mm) and thin films were measured. The cure of the thin specimens was determined using changes in resin volume as well as by an infrared spectroscopic method. The cure of thin specimens of a comm ercially available unfilled bonding resin was also determined using th e shrinkage method and by conventional infrared spectroscopic methods. Results. There was no difference (p = 0.0617) between cure values of the commercial resin using either conventional IR methods or the shrin kage methods. For each copolymer combination of thin films, there was also no significant difference in the extent of cure between the IR me thod used and the shrinkage method presented (lowest p-value 0.29). Th e cure of TEGDMA/MMA copolymer bar specimens demonstrated a decreasing trend of cure with increasing proportion of TEGDMA, and had cure valu es which were similar to others reported in the literature. Significan ce. The evidence from this study demonstrated that the specimen volume method can be used to determine the extent of resin cure of thin film or bulk resin specimens. This method represents an easily performed p rocedure that can be used by all investigators without expensive equip ment.