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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

A comparative study between crack analysis and a mechanical test for assessing the polymerization stress of restorative composites

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Author(s):
Braga, Roberto R. [1] ; Yamamoto, Takatsugu [2] ; Tyler, Kenneth [3] ; Boaro, Leticia C. [1] ; Ferracane, Jack L. [4] ; Swain, Michael V. [3]
Total Authors: 6
Affiliation:
[1] Univ Sao Paulo, Sch Dent, Dept Dent Mat, Sao Paulo - Brazil
[2] Tsurumi Univ, Sch Dent Med, Dept Operat Dent, Yokohama, Kanagawa - Japan
[3] Univ Sydney, Fac Dent, Biomat Sci Res Unit, Sydney, NSW 2006 - Australia
[4] Oregon Hlth & Sci Univ, Sch Dent, Dept Restorat Dent, Div Biomat & Biomech, Portland, OR 97201 - USA
Total Affiliations: 4
Document type: Journal article
Source: Dental Materials; v. 28, n. 6, p. 632-641, JUN 2012.
Web of Science Citations: 17
Abstract

Objectives. To verify the hypothesis that crack analysis and a mechanical test would rank a series of composites in a similar order with respect to polymerization stress. Also, both tests would show similar relationships between stress and composite elastic modulus and/or shrinkage. Methods. Soda-lime glass discs (2-mm thick) with a central perforation (3.5-mm diameter) received four Vickers indentations 500 mu m from the cavity margin. The indent cracks were measured (500x) prior and 10 min after the cavity was restored with one of six materials (Kalore/KL, Gradia/GR, Ice/IC, Wave/WV, Majesty Flow/MF, and Majesty Posterior/MP). Stresses at the indent site were calculated based on glass fracture toughness and increase in crack length. Stress at the bonded interface was calculated using the equation for an internally pressurized cylinder. The mechanical test used a universal testing machine and glass rods (5-mm diameter) as substrate. An extensometer monitored specimen height (2 mm). Nominal stress was calculated dividing the maximum shrinkage force by the specimen cross-sectional area. Composite elastic modulus was determined by nanoindentation and post-gel shrinkage was measured using strain gages. Data were subjected to one-way ANOVA/Tukey or Kruskal-Wallis/Mann-Whitney tests (alpha: 5%). Results. Both tests grouped the composites in three statistical subsets, with small differences in overlapping between the intermediate subset (MF, WV) and the highest (MP, IC) or the lowest stress materials (KL, GR). Higher stresses were developed by composites with high modulus and/or high shrinkage. Significance. Crack analysis demonstrated to be as effective as the mechanical test to rank composites regarding polymerization stress. (c) 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. (AU)

FAPESP's process: 09/16267-0 - Crack propagation in the surrounding structure caused by composite polymerization stress: local and material-related effects
Grantee:Roberto Ruggiero Braga
Support type: Scholarships abroad - Research