INFLUENCE OF POST CURING HEAT AND PRESSURE ACTIVATION FOR RESIN COMPOSITE ON IT’S SURFACE HARDNESS

This study was conducted to evaluate the influence of post curing heat and pressure activation of resin composite on it’s surface hardness.
Materials and methods: A total of 30 disc specimens, 7mm in diameter and 2mm thick, were constructed from 3 different types of contemporary resin composite restoratives (10 each). For each restorative, half the numbers of the constructed specimens (5 discs) were served as directly cured composite, following their storage in water at 37±1oC for 24h. The remaining 5 specimens of each restorative were subject to post-curing heat and pressure in type B Lisa autoclave for 41 min using B-universal 121 cycle at 122.5ºC and a pressure of 1.16 bar to simulate one simple approach of chair-side indirect composite polymerization. Vickers hardness numbers were determined using a micro-hardness tester (Wilson ® Hardness Tester, Model Tukon 1102, Buehler, Lake Bluff, IL, USA) using a load of 50 gf for 15 seconds dwell time. The Vickers’s hardness number (N/mm2) was recorded as an average of six readings, three from each surface (top and bottom) for each specimen.
Results: ANOVA was used for the effect of additional heat activation and type of resin composite on it’s surface hardness. It was found that the use of an additional heat activation and type of resin composite (matrix type and degree of loading) had a statistical significant effect on VHN of resin composite tested.
Conclusion: The post-curing heat and pressure improves the surface hardness of the tested resin composites.