Influence of temperature and primer application on setting time and degree of conversion of a dual-cure self-adhesive...

To examine the in vitro effect of different temperatures and use of a primer on the setting time (ST) and degree of conversion (DC) of a novel dual-cure self-adhesive cement (Set Maxx, SDI Limited).

Set Maxx was tested alone or with Stela Primer (SDI), both with light curing (LC) for 20 s with the Valo X (Ultradent), or it was allowed to self-cure (SC). The ST was determined according to ISO 4049 (n = 5). To measure DC, the cement was dispensed onto a temperature-controlled ATR sensor on an FT-IR spectrometer set at 23 °C, 32 °C, or 37 °C. The rates of polymerization and DC were measured for 1800 s (n = 4). The temperature increase was also measured at the bottom using a K-type thermocouple (n = 3). The results were compared using ANOVA and Tukey's multiple comparison test (α=0.05).

The setting time was longer for the 23 °C group that used no primer (149 s ± 2.6). The highest DC was observed when using the primer at 37 °C in the SC (75.1 % ± 2.2) and LC (76.5 % ± 1.8) groups. Light exposure had a negligible effect on the final DC; however, it had the most significant impact on the maximum rate of change in the DC during polymerization. This was likely due to heat from the light, with the highest rate for the LC group at 37 °C (7.7 %/s ± 0.4) and a temperature increase of 41.7 °C ± 3.2.

Compared to using no Primer and at a temperature of 23 °C, using 37 °C and Stela Primer enhanced the DC of Set Maxx. Light exposure alone did not substantially increase the final DC, but it did increase the reaction rate and accelerate the polymerization.

Combining the Stela Primer with light exposure achieved the highest DC in Set Maxx. Laboratory studies conducted at room temperature should be reevaluated and repeated at intraoral temperatures.