Effects of different polymerization protocols on the degree of conversion of two dual‐cured core buildup composites polymerized by light‐emitting diode and halogen light‐curing units

Abstract

The aim of study was to investigate the effects of various curing protocols with quartz–tungsten halogen (QTH) or light‐emitting diode (LED) light‐curing units on the degree of conversion (% DC) of two dual‐cured core buildup resin composites. Two dual‐cured core buildup resin composites, Clearfil Dc Core Automix (CLF) and Grandio Core Dc (GR), were selected. Specimens were exposed to the polymerization protocols as follows: there was immediate photoactivation or photoactivation delayed by 2 or 5 min by a QTH or LED source, and one group was allowed to chemically polymerize and served as a control (n = 6). The % DC of the specimens was determined with attenuated total reflectance–Fourier transform infrared spectroscopy. The GR samples polymerized with QTH for the 5‐min‐delayed photoactivation had higher % DC values than those self‐cured, and the Clearfil Dc Core Automix (CLF) samples with immediate or delayed curing protocols with halogen yielded higher % DC values than the samples that were chemically polymerized. The comparison of the two resin composites polymerized with halogen showed a higher % DC for CLF than for GR in the 2‐min‐delayed photoactivation. On the other hand, when they were cured with LED, the % DC values of GR significantly increased after the 2‐min‐delayed photoactivation. In light of the results, it might be stated that CLF polymerized with QTH, could be the better option. GR provided adequate chemical polymerization; therefore, it might be useful in areas in which light curing is not possible. Clinicians should consider the polymerization characteristics of dual‐cured resin composites. The use of different composites may require the modification of the application procedures recommended by the manufacturer. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40560.

Hardness Development in Resin Composite Core Materials

“…The Knoop hardness values for Fluorocore 2+ are similar to those reported by Arrais et al, 15 slightly more than those reported by Tauböck et al in regards to Multicore Flow, 44 and similar to those reported for Rebilda DC tooth colored material. 44 Clearfil DC Core values in this study approximate those published by Yoshida and Meng 10 but are less than those reported by Karakis et al 11 In regards to the dual cure core material self-cure results, this study contrasts those described by Tauböck et al, 6 Schmage et al, 11 and Karakis et al 39 Some variance could be related to different curing regimens and specimen thickness variations. However, these differences cannot be fully explained at this time and can be the subject for future studies.…”

“…36,37 Accordingly, mixed reports exist concerning the self-cure performance of resin composite dual-cure materials. Studies have reported that resin dual-cure cement materials may not reach similar degree of polymerization when evaluated in the absence of light activation, 38,39 contrasted by other works providing evidence that some dual-cure core materials have similar self-cure mode curing as that observed with photopolymerization. 6,11 Under the conditions of this study, no product under self-cure conditions attained similar hardness to that observed of the photopolymerized top surface of the same product.…”