Author Name : Dr. Ritu Kadyan
Publisher Name : ER Publications, India
Aim: This in-vitro study is aimed to investigate the influence of the different curing distances (0mm, 3mm, 6mm and 9mm) in terms of surface microhardness (KHN) of different resin composites.
Materials and Methods: The materials tested were Microhybrid composite- Esthet X HD (Dentsply), Nanohybrid composite- Filtek Z250 (3M ESPE, St. Paul, MN, USA), Nanofilled composite- Filtek Z350 (3M ESPE, St. Paul, MN, USA). 40 specimens of each material was prepared by using the cut dentin section with a hole (with internal dimentions 3.5mm in diameter and 2mm in height) which act as a natural mold. The subgroups were divided according to the distance in mm of the light cure gun tip from the composite resin surface (0 mm, 3 mm, 6 mm, and 9 mm). Samples were subjected to a load of 100 gf (gram force) with a dwell time of 15 seconds to the central top surface of each sample via an Indentator to check surface microhardness which was carried out using a Digital Microhardness Tester to attain Knoop Hardness Value (HV).
Results: Comparing the mean difference in surface microhardness for Filtek Z350 in different simulating groups, Filtek Z350 showed the maximum microhardness as compared to Filtek Z250 but there was no statistical difference seen between these two. The Esthet X HD showed minimum microhardness with statistically significant difference when compared with Filtek Z350 samples and Filtek Z250.
Conclusion: The nano composites might be considered better in terms of surface hardness as compared to micro hybrids. The KHN values of almost all resin composites decreased with the increase in light source distance from the resin composite surface.