Document Type : Original Article
Authors
1 Assistant Professor, Department of Operative Dentistry, School of Dentistry, Shiraz University of Medical Sciences
2 Dentist
Abstract
Statement of Problem: Postcuring techniques improve mechanical properties of indirect composites significantly. Eventhought this technique has been suggested for direct composites, but its effect for direct composites is still questionable.Purpose: This study was undertaken to evaluate the effect of various postcuring techniques on surface hardness of two different types of composites.Materials and Method: Eighty circular specimens of Nulite F (40 specimens) and Gradia (40 specimens) composites were made and light cured. Ten of each type was kept as control group and 10 of each type was postcured with oven for 5 minutes at 120°C. The other ten ones was postcured with microwave for 5 minutes and the last 10 ones were postcured with labolite for 5 minutes. The specimens were polished and were kept in 37°C water for one week. Then surface hardness testing was performed and data were analyzed using one-way ANOVA and Kruskal wallis tests.Results: The results revealed that the surface hardness (VHN) of Nulite F composite in control group was greater than Gradia composite in control group (p<0.05). All postcuring techniques increased the VHN of all groups significantly. The effects of postcuring on increasing surface hardness of Nulite F were more significant in all techniques, especially by the usage of labolite set in Nulite F composite in comparison with Gradia composite. There was no statistically significant difference between surface hardness of microwave and oven groups in Nulite F composite. No statistically significant difference was noticed between surface hardness of microwave and labolite groups in Gradia composite. The effect of postcuring with oven on surface hardness of Gradia composite was statistically significant compared to the two other techniques.Conclusion: By evaluation of various samples in this study it was concluded that all postcuring techniques (labolite, microwave and oven) increased the surface hardness (VHN) of both direct composites (Gradia and Neulife F) significantly. Key words: Postcuring, Surface hardness, Microwave, Oven, Labolite, Direct composite
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