Thermal degradation of photo-polymerized BisGMA/TEGDMA-based dental resins

Abstract The thermal behavior of BisGMA/TEGDMA-based dental resins of various degrees of conversion was examined using differential scanning calorimetry (DSC), thermogravimetric-gas chromatography mass spectrometry (TG-GC/MS), and thermogravimetric-mass spectrometry (TG-MS). This study identified pyrolysates of BisGMA/TEGDMA copolymers from mass spectra. Three phases (initial, second, and final phases) of thermal degradation appeared in the TGA and derivative TGA (dTGA) curves. The thermal degradation mechanism in each phase was explained by the thermal behavior of four pyrolysates: methacrylic acid, 2-hydroxyethel methacrylate, propionic acid, and phenol. The thermal characteristics of copolymers of various degrees of conversion were determined from the temperatures at the intersections of the curves of the second and final phase separated from dTGA curves. Regression analysis revealed a very strong correlation ( R 2 =0.942) between the degree of copolymer conversion and the temperature at the intersection.