Post-curing conversion kinetics as functions of the irradiation time and increment thickness

Objective: this study evaluated the variation of conversion degree (dc) in the 12 hours following initial photoactivation of a low-shrinkage composite resin (venus diamond). material and methods: the conversion degree was monitored for 12 hours using attenuated total reflection (atr) f-tir spectroscopy. the composite was placed in 1 or 2 mm rings and cured for 10 or 20 seconds with a led lamp. atr spectra were acquired from the bottom surface of each sample immediately after the initial photoactivation (p=0),30 minutes (p=0.5) and 12 hours after photoactivation (p=12) in order to obtain the dc progression during the post-curing period. interactions between thickness (t),irradiation time (i) and post-curing (p) on the dc were calculated through anova testing. results: all the first order interactions were statistically significant,with the exception of the t-p interaction. furthermore,the shift from p=0 to p=0.5 had a statistically higher influence than the shift from p=0.5 to p=12. the post-curing period played a fundamental role in reaching higher dc values with the low-shrinkage composite resin tested in this study. moreover,both the irradiation time and the composite thickness strongly influenced the dc. conclusions: increased irradiation time may be useful in obtaining a high conversion degree (dc) with a low-shrinkage nano-hybrid composite resin,particularly with 2 mm composite layers.