Post-irradiation polymerization of composites containing bis-GMA and TEGDMA

Objective: This study was conducted to evaluate the effect of the amount of TEGDMA on post-irradiation polymerization of bis-GMA based composites. Methods: Four experimental composites containing bis-GMA and TEGDMA at the ratios (w/w) of 75/25, 70/30, 67/33, and 50/50 were prepared. The degree of conversion of each composite was measured by Fourier transformation infrared spectroscopy immediately after being cured and after 24 h of storage, and the post-irradiation polymerization was determined. In addition, the change in respective amounts of residual bis-GMA and TEGDMA in cured specimens over 24 h was determined by high performance liquid chromatography. Data were analyzed by means of ANOVA, followed by a Fisherʹs PLSD test at a significance level of 0.05. Results: At both stages of as-cured and after 24 h-storage, the composites containing greater amounts of TEGDMA showed a greater degree of conversion. The amount of post-irradiation polymerization decreased as the content of the incorporated TEGDMA increased. The reduction in the amount of TEGDMA remaining unreacted during post-irradiation polymerization also decreased as the content of TEGDMA increased, while the amount of unreacted bis-GMA showed almost constant values. Significance: An increase in the amount of TEGDMA-incorporation in bis-GMA based composites resulted in less post-irradiation polymerization. As the change in the amount of residual unreacted TEGDMA in cured specimens showed the same trend as the results of the post-irradiation polymerization, TEGDMA is considered to be the main contributor to post-irradiation polymerization of bis-GMA based composites.