Effect of curing mode on immediate and post-irradiation depth of cure of a silorane-based and methacrylate- based posterior composites (in vitro comparative study)

Abstract

Background: Incomplete polymerization of composite restorations compromises the restoration both mechanically and biologically. Recently, composite curing lights have been developed that have higher intensities and shorter curing cycles which help speed the resin-based curing. This study was conducted with the aim of evaluating the effect of conventional and high intensity light curing units on the depth of cure of three different types of composite resin. Materials and Method: Forty eight cylindrical specimens 4mm in diameter and 8mm in height were prepared from three types of composite resin (Filtek™ P60,Tetric EvoCeram and Filtek™ P90) using a two-piece aluminum mold. Half of the specimens were cured with a QTH for 40 seconds, while the other half of the specimens were cured with the FlashMax P3 high intensity light curing unit for 3 seconds. The cured specimens of each composite type were then subdivided into three subgroups of eight specimens each according to the aging period prior to curing depth measurement (immediate, after 24 hours, or after 7 days). The depth of cure was measured using the scraping method (scratch test). Results: The results of this study showed that Filtek™ P60 showed the highest mean depth of cure, followed by Tetric EvoCeram and Filtek™ P90 which showed the lowest curing depth regardless of the curing mode or aging period, and the difference was statistically highly significant (p< 0.01). The results of the study also showed that the specimens cured with the QTH had higher curing depth than those cured with the FlashMax P3 regardless of the composite type and aging period and the difference was also statistically highly significant (p< 0.01). Concerning the effect of aging, there was an increase in curing depth till 24 hours for Filtek™ P60 and Tetric EvoCeram, while for Filtek™ P90 the increase in curing depth continued till 7 days. Conclusions: The packable composite Filtek™ P60 showed the highest curing depth as compared with the nanofilled composite Tetric EvoCeram and the silorane-based composite Filtek™ P90. However, there was a continuous increase in curing depth of the silorane-based composite with time. All composite resins cured with the conventional QTH light curing unit presented higher curing depths than those cured with the FlashMax P3 high intensity light curing unit.