Dentin μTBS and Hardness of Bulk-fill and Conventional Composites Placed in a Box-shaped Cavity Preparation.


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Dentin μTBS and Hardness of Bulk-fill and Conventional Composites Placed in a Box-shaped Cavity Preparation.

J Adhes Dent. 2017 Nov 17;:1-6

Authors: Silame FDJ, Geraldeli GP, Sinhoreti MAC, Pires-de-Souza FCP, Roulet JF, Geraldeli S

Abstract
PURPOSE: To compare the dentin microtensile bond strength (μTBS) and the Knoop hardness of bulk-fill and conventional restorative composites in box-shaped Class I cavities using different insertion techniques.
MATERIALS AND METHODS: Forty box-shaped Class I preparatons 4 mm deep were performed in the pulp chamber of sound human third molars. The restorations were made using either a conventional microhybrid (Z250, 3M ESPE) or bulk-fill (Tetric EvoCeram Bulk-fill, TCBF) composite using two incremental thicknesses: 2 mm or 4 mm (n = 10). After 24-h water storage, the restorations were sectioned. The first slice (0.7 mm thick) taken from a proximal surface was submitted to the Knoop hardness (KHN) test at five depths from the occlusal cavosurface to the pulpal line angle. Sticks were fabricated from the remaining sections and tested for dentin microtensile bond strength (μTBS). Means were analyzed using two-way ANOVA and Tukey's test (p < 0.05).
RESULTS: Higher (p < 0.05) μTBS resulted when both composites were restored with 2-mm increments, with no significant difference between materials (p > 0.05). Higher (p < 0.05) KHN means were found when 2-mm increments were used, with no significant differences (p > 0.05) between the materials. When the teeth were restored with one bulk increment (4 mm), the deeper layers presented lower KHN means (p < 0.05) starting at 2 mm for Z250 and 3 mm for TCBF.
CONCLUSION: The 2-mm increment restorations in box-shaped cavities yielded higher μTBS and microhardness for conventional and bulk-fill composites.

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