Effect of Shelf Storage Temperature and Curing Time on the Microhardness of Zirconium Containing Nano-Hybrid Resin Composite: An in Vitro Study
Krishna Prasadl L
Department of Conservative Dentistry & Endodontics, KVG Dental College & Hospital, Sullia, India.
Safiya Nikhat
*
Department of Conservative Dentistry & Endodontics, KVG Dental College & Hospital, Sullia, India.
*Author to whom correspondence should be addressed.
Abstract
Background: Adequate polymerization is essential for attaining optimal mechanical strength and ensuring improved clinical performance of composite restorative materials. Surface hardness is a critical characteristic of resin composites, as it determines their ability to withstand plastic deformation, indentation, and surface abrasion. This property is essential for maintaining esthetic integrity and also reflects the material’s suitability for efficient finishing and polishing procedures.
Objective: The purpose of this study is to evaluate the effect of shelf storage temperature and different curing time on microhardness of composite.
Materials and methods: Specimens were divided into 3 groups. Group I storage at room temperature, Group II storage in refrigerator and Group III: 30 minutes post removal from refrigeration. A total of 36 disc-shaped resin-based composite (RBC) specimens, each measuring 2 mm in thickness and 5 mm in diameter, were prepared using a single restorative material (ESCOM 250). Again, specimens were divided into 2 subgroups. Subgroup A underwent light curing for 10 seconds, whereas Subgroup B was light cured for 20 seconds using an LED curing unit through a Mylar strip and glass slide. The prepared specimens were then subjected to Vickers microhardness testing.
Results: For Group I and Group III, curing for 20 seconds results in significantly higher microhardness for both top and bottom surfaces (P- Value < 0.05). This suggests that a 20-second curing time is more effective than 10 seconds. Specimens that were refrigerated and cured for 10seconds exhibited the lowest microhardness suggesting that both factor storage temperature and curing duration are interdependent.
Conclusion: Temperature and light-curing time significantly impact the surface microhardness of composite materials, with variations in these factors affecting microhardness values.
Keywords: Composite resin, microhardness, storage temperature, curing time