Abstract
Objective The aim of this study is to evaluate the microhardness and surface roughness of two different bulk-fill composites polymerized with light-curing unit (LCU) with different polymerization times before and after the application of a home bleaching agent. Materials-Methods For both microhardness and surface roughness tests, 6 groups were prepared with bulk-fill materials (SonicFill, Filtek Bulk Fill) according to different polymerization times (10, 20, and 30 s). 102 specimens were prepared using Teflon molds (4 mm depth and 5 mm diameter) and polymerized with LCU. 30 specimens (n = 5) were assessed for microhardness. Before home bleaching agent application, the bottom/top (B/T) microhardness ratio was evaluated. After bleaching agent application, the microhardness measurements were performed on top surfaces. Roughness measurements were performed in 72 specimens (n = 12) before and after bleaching application. Additionally, for SEM analyses, two specimens from all tested groups were prepared before and after bleaching agent application. The data B/T microhardness ratio before bleaching was analyzed by two-way ANOVA and Tukey's HSD test. The data from the top surface of specimens' microhardness before and after bleaching were analyzed using Wilcoxon signed-rank test, Kruskal-Wallis, Mann-Whitney U tests. The data from surface roughness tests were statistically analyzed by multivariate analysis of variance and Bonferroni test (p < 0.05). Results The B/T microhardness ratio results revealed no significant differences between groups (p > 0.05). Comparing the microhardness values of the composites' top surfaces before and after bleaching, a significant decrease was observed exclusively in FB30s (p < 0.05). No significant differences in surface roughness values were observed when the groups were compared based on bulk-fill materials (p > 0.05) while the polymerization time affected the surface roughness of the SF20s and SF30s groups (p < 0.05). After bleaching, surface roughness values were significantly increased in the SF20s and SF30s groups (p < 0.05). Conclusion The clinicians should adhere to the polymerization time recommended by the manufacturer to ensure the durability of the composite material in the oral environment.
Highlights
Resin-based composite (RBC) is one of the most commonly used materials in restorative dentistry
The second aim of this study is to evaluate the effect of home bleaching agent on the microhardness and surface roughness of two bulk-fill composites with different polymerization times
Different capital letters show the significant differences between the same columns (p < 0 05)
Summary
Resin-based composite (RBC) is one of the most commonly used materials in restorative dentistry. RBC composition has significantly improved, leading to better esthetics, mechanical properties, and clinical durability. Manufacturers have introduced bulk-fill resin-based composite materials that can fill cavities up to 4–6 mm at once [1]. Optimum polymerization to the full depth of the RBC is very important to obtain proper mechanical and physical properties. Polymerization of the restoration is directly related to the material’s organic and inorganic composition as well as the type and morphology of the filler contents [2]. Polymerization is influenced by the polymerization time, light spectrum, and distance of the restoration to the light-curing unit [3,4,5]. Hardness measurement has been shown to be a practical and indirect method determining
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