Volume 129, Issue 6 e12825
ORIGINAL ARTICLE

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

Daniella Cristo Santin

Daniella Cristo Santin

Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo-USP, Bauru, SP, Brazil

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Marilia Mattar de Amoêdo Campos Velo

Marilia Mattar de Amoêdo Campos Velo

Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo-USP, Bauru, SP, Brazil

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Francielly da Silva Camim

Francielly da Silva Camim

Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo-USP, Bauru, SP, Brazil

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Nair Cristina Margarido Brondino

Nair Cristina Margarido Brondino

Faculty of Science, Department of Mathematics, São Paulo State University-UNESP, Bauru, SP, Brazil

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Heitor Marques Honório

Heitor Marques Honório

Department of Pediatric Dentistry, Orthodontics and Public Health, Bauru School of Dentistry, University of São Paulo-USP, Bauru, SP, Brazil

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Rafael Francisco Lia Mondelli

Corresponding Author

Rafael Francisco Lia Mondelli

Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo-USP, Bauru, SP, Brazil

Correspondence

Rafael Francisco Lia Mondelli, Alameda Octávio Pinheiro Brisolla St., 9–75, Bauru, SP, Zip Code: 17012-901, Brazil.

Email: [email protected]

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First published: 05 December 2021
Citations: 2

Abstract

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 mm3) and five specimens with 4 mm thickness (C-factor 0.375 and volume 48 mm3) 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.

CONFLICT OF INTEREST

The authors declare no financial and/or personal interest that could affect this study.

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