Comparative evaluation of the micro-hardness and compressive strength of two composite materials cured with halogen and led light curing units

Resin based composite restorations placed instead of amalgam continue to increase owing to their esthetics and good functional properties, in restorations involving both anterior and posterior teeth. A good clinical performance depends on the physical and chemical properties which are directly related to conversion of the monomers into polymers. Compressive strength is important for clinical success since it directly affects the physical properties and longevity of restorations. The degree of monomer conversion of resin composite can be measured using different testing techniques- direct or indirect methods. In the present invitro-study indirect methods such as surface micro-hardness and compressive strength were used Aim: Evaluate and compare - micro hardness and compressive strength of Bulkfill and Nano-hybrid composite cured with QTH (quartz tungsten halogen) and LED (light emitting diode) light curing units. Materials and Methods: 80 specimens of standard dimension (4mm diameter and 1.5mm depth) were obtained from a transparent teflon mould. The specimens were divided into 2 main groups, each specimen then being filled with a light cure composite resin (3M ESPE bulkfill and nano-hybrid) and cured with LED and QTH light curing units for 40 seconds each. Physical properties like the compressive strength and surface micro-hardness was evaluated using Instron machine, Vickers hardness testing machine as specified in the ISO standard for resin based composite, ISO 4049:2000. Result: Statistical analysis was employed using Student t-test. All the tested groups showed a significant difference from each other when the level of significance was set at 0.05. Conclusion: Composites when cured using LED light curing units appear to have better compressive and micro-hardness levels thus validate a greater potential in clinical applications.