Effect of thickness on shrinkage stress and bottom-to-top hardness ratio of conventional and bulk-fill composites.

Autor: Santin DC; Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo-USP, Bauru, SP, Brazil., Velo MMAC; Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo-USP, Bauru, SP, Brazil., Camim FDS; Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo-USP, Bauru, SP, Brazil., Brondino NCM; Faculty of Science, Department of Mathematics, São Paulo State University-UNESP, Bauru, SP, Brazil., Honório HM; Department of Pediatric Dentistry, Orthodontics and Public Health, Bauru School of Dentistry, University of São Paulo-USP, Bauru, SP, Brazil., Mondelli RFL; Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo-USP, Bauru, SP, Brazil.
Jazyk: angličtina
Zdroj: European journal of oral sciences [Eur J Oral Sci] 2021 Dec; Vol. 129 (6), pp. e12825. Date of Electronic Publication: 2021 Dec 05.
DOI: 10.1111/eos.12825
Abstrakt: This study evaluated the effect of the material thickness on shrinkage stress and bottom-to-top hardness ratio of conventional and bulk-fill composites. Six commercial composites were selected based on their different technologies: Two conventional (C1, C2), two high-viscosity bulk-fill (HVB1, HVB2), and two low-viscosity bulk-fill (LVB1, LVB2). Shrinkage stress was analyzed for five specimens with 2 mm thickness (C-factor 0.75 and volume 24 mm 3 ) and five specimens with 4 mm thickness (C-factor 0.375 and volume 48 mm 3 ) for 300 s in a universal testing machine. Bottom-to-top hardness ratio values were obtained from Knoop microhardness measurements in specimens with 2- and 4-mm thickness (n = 5). Thickness increase resulted in significantly higher shrinkage stress for all materials with the exception of HVB2 and LVB1. C1, C2, HVB2, and LVB1 showed lower bottom-to-top hardness ratios at 4 mm than at 2 mm. Only LVB2 presented a bottom-to-top hardness ratio lower than 80% at 2 mm, while HVB1 surpassed this threshold at 4 mm of depth. The results suggest that the increase of composite thickness affected the shrinkage stress values. Also, thickness increase resulted in lower bottom-to-top hardness ratio. HVB1 showed better behavior than other bulk-fill materials, with low stress and adequate bottom-to-top hardness ratio at 4 mm thickness.
(© 2021 Scandinavian Division of the International Association for Dental Research. Published by John Wiley & Sons Ltd.)
Databáze: MEDLINE
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