Caspian Journal of Dental Research

Introduction:Discoloration of the resin-based composites is a common problem in restorative dentistry. There are many factors associated with the discoloration of dental materials in the oral environment. The purpose of this study was to evaluate the color changes in a nano-composite cured with a quartz-tungsten-halogen (QTH) and light emitting diode (LED) unit.

Methods:80 disk-shaped specimens were prepared using Filtek Z350 XT.The specimens were cured with two LED units (Valo and BluephaseC5) and QTH ) Astralis7 ( with two different energy density (400 & 750 mW/Cm²). The color of the materials was measured before and after immersing in tea and artificial saliva. Color change value (ΔE) were calculated and analyzed by 2-way ANOVA and Tukey’s test.

Results: In artificial saliva group, the composites cured with Astralis7 and BluephaseC5 showed significantly more color stability. In tea group, the composites cured with BluephaseC5 significantly had the least color change.

Conclusions: The type of light curing unit does not affect the color stability. Exposure time and interaction between light source and photo initiator content in composite may be the most important factors affecting color stability.

Introduction: The present study was performed to evaluate the effects of light-curing modes and shades of methacrylate and silorane-based composite resins on temperature rise during polymerization of composite resins.

Materials &Methods: In this in vitro study, ninety composite samples with two types of composite resin - methacrylate-based and a low-shrinkage silorane-based were prepared, in 3 groups (30 samples in each group), Group 1: Filtek Z250 (shade A3), Group 2: Filtek Z250 (shade B2) and Group 3: Filtek P90 (shade A3). To evaluate temperature changes, 15 samples and the other half were light-cured using the standard and soft start curing modes for 40 seconds, respectively. A k-type thermocouple was used to recorded temperature changes.

Results: Temperature rise in the silorane-based composite resin group (group 3) was higher than that in the methacrylate-based one (group 1) (P<0.001). Temperature rise with the darker shade (group 1) was higher than that with lighter shade (group 2) (P<0.001). Standard curing resulted in more temperature rise compared to soft start curing; however, the difference was only significant in group 2 (P<0.001). In all groups, temperature increased with an increase in curing time and the temperature rise pattern during the first 10 seconds with the soft start curing was not consistent with the standard curing (in group 2 and 3); the temperature rise pattern was milder than the soft start curing (P<0.001).

Conclusion: Factors such as composite resin type, shade and curing mode affected temperature changes in composite resins evaluated in the present study.