Effect of temperature on post-cure polymerization of bulk-fill composites

To investigate the 24h post-cure polymerization and the effect of temperature on the post-cure polymerization of one conventional and three bulk-fill composite materials.

A conventional composite GrandioSO (GR) and three bulk-fill composites: Tetric EvoCeram Bulk Fill (TECBF), Quixfil (QF) and X-tra fil (XF) were investigated. The samples were cured for 20s with irradiance of 1090mW/cm(2). Composite samples were divided into two groups: the "room-temperature" group (RT, n=5) and the "body-temperature" group (BT, n=5) and they were stored in dark at 20°C and 37°C, respectively. Measurements of degree of conversion (DC) were made immediately after curing (0h) and 24h post-cure (24h). To analyse the extent of post-cure DC increase, the DC values of 0h-RT/24h-RT and 0h-BT/24h-BT were compared. To analyse the difference in DC between RT and BT, the DC values of 0h-RT/0h-BT and 24h-RT/24h-BT were compared.

DC increase 24h post-cure was significant for all composites and ranged between 6.3% and 8.2% in RT and between 12.5% and 15.7% in BT. All composites demonstrated a higher DC in 24h-BT compared to 24h-RT. The difference was statistically significant for GR, TECBF and QF.

All composites demonstrated a significant post-cure effect after 24h. Post-cure temperature increase from 20°C to 37°C yielded a higher post-cure DC increase.

Due to the temperature effect on the final DC, studies performed at composite samples at room temperature may record more inferior properties than these attained in the oral cavity.