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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.)

BisGMA/TEGDMA ratio and filler content effects on shrinkage stress

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Author(s):
Goncalves, Flavia [1] ; Azevedo, Caio L. N. [2] ; Ferracane, Jack L. [3] ; Braga, Roberto R. [1]
Total Authors: 4
Affiliation:
[1] Univ Sao Paulo, Sch Dent, Dept Dent Mat, BR-05508000 Sao Paulo - Brazil
[2] Univ Estadual Campinas, Dept Stat, Inst Math Stat & Comp Sci, Campinas, SP - Brazil
[3] Oregon Hlth & Sci Univ, Sch Dent, Dept Restorat Dent, Div Biomat & Biomech, Portland, OR 97201 - USA
Total Affiliations: 3
Document type: Journal article
Source: Dental Materials; v. 27, n. 6, p. 520-526, JUN 2011.
Web of Science Citations: 65
Abstract

Objective. To investigate the contributions of BisGMA:TEGDMA and filler content on polymerization stress, along with the influence of variables associated with stress development, namely, degree of conversion, reaction rate, shrinkage, elastic modulus and loss tangent for a series of experimental dental composites. Methods. Twenty formulations with BisGMA: TEGDMA ratios of 3: 7, 4: 6, 5: 5, 6: 4 and 7: 3 and barium glass filler levels of 40, 50, 60 or 70 wt% were studied. Polymerization stress was determined in a tensilometer, inserting the composite between acrylic rods fixed to clamps of a universal test machine and dividing the maximum load recorded by the rods cross-sectional area. Conversion and reaction rate were determined by infra-red spectroscopy. Shrinkage was measured by mercury dilatometer. Modulus was obtained by three-point bending. Loss tangent was determined by dynamic nanoindentation. Regression analyses were performed to estimate the effect of organic and inorganic contents on each studied variable, while a stepwise forward regression identified significant variables for polymerization stress. Results. All variables showed dependence on inorganic concentration and monomeric content. The resin matrix showed a stronger influence on polymerization stress, conversion and reaction rate, whereas filler fraction showed a stronger influence on shrinkage, modulus and loss tangent. Shrinkage and conversion were significantly related to polymerization stress. Significance. Both the inorganic filler concentration and monomeric content affect polymerization stress, but the stronger influence of the resin matrix suggests that it may be possible to reduce stress by modifying resin composition without sacrificing filler content. The main challenge is to develop formulations with low shrinkage without sacrificing degree of conversion. (C) 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. (AU)