DENTAL MATERIALS
EFFECT OF THERMAL CYCLING ON MICROHARDNESS VALUES OF RESIN COMPOSITES WITH DIRECT AND INDIRECT INDICATIONS CURED BY DIFFERENT POLYMERIZATION TECHNIQUES
https://doi.org/10.25241/stomaeduj.2023.10(1-4).art.2
Abstract
Introduction
The present in vitro study investigated the effects of cyclic temperature changes on the surface hardness of composite resins that could be used indirectly and cured by different polymerization methods.
Methodology
A total of 200 disc-shaped samples (5 mm x 2 mm) were prepared from resin composites with indirect indications (ENA HRi Bio Function [BF], Enamel Plus HRi [HRI]), an indirect composite (Gradia Plus [GR]), and a direct composite (Herculite XRV Ultra [HL]). Composite samples were divided into subgroups according to the 20- or 60 seconds polymerization methods with either a light emitting diode (LED), halogen curing units, or a dual mode light curing unit (Labolight DUO) (n=10). Then, the specimens were subjected to ageing through 5000 thermal cycles at temperatures alternating between 5°C and 55°C with a dwelling time of 30 seconds in water baths. Finally, all samples were subjected to hardness testing using a digital microhardness tester. Scores in Vickers values were analyzed statistically using the ANOVA and Bonferroni tests at p<0.05.
Results Thermal cycling had significantly affected the microhardness values of groups polymerized with both the halogen (GR- 60 seconds, HRI- 60 seconds) and LED units (HRI- 60 seconds). Dual mode curing had significantly increased the microhardness scores of HRI and HL groups (p<0.05). Among all groups, regardless of the curing time or unit, BF had the highest microhardness scores.
Conclusion
Although thermal cycling had significantly affected the microhardness scores of some groups of composite resins with indirect indications, its efficiency could be reported as inconsiderable.
Keywords: Dual mode curing; Polymerization; Microhardness; Resin composites; Thermal cycling;