Finite element analysis of bonded model Class I ‘restorations’ after shrinkage

Rodrigues, Flávia P.; Silikas, Nick; Watts, David C.; Ballester, Rafael Y.

doi:10.1016/j.dental.2011.10.001

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Volume 28, Issue 2 , Pages 123-132, February 2012

Finite element analysis of bonded model Class I ‘restorations’ after shrinkage

Flávia P. Rodrigues
- Biomaterials Research Group, School of Denstistry, Anhanguera-Bandeirante University of São Paulo, São Paulo, Brazil
- Corresponding author at: Anhanguera-Bandeirante University of São Paulo, School of Dentistry, R. Maria Cândida, 1813 Bloco G, 6th Floor, V. Guilherme 02071-013, São Paulo, SP, Brazil. Tel.: +55 11 2967 9058; mobile: +55 11 9492 1334.
Nick Silikas
- Biomaterials Science Research Group, School of Dentistry, The University of Manchester, Manchester, United Kingdom
David C. Watts
- Biomaterials Science Research Group, School of Dentistry, The University of Manchester, Manchester, United Kingdom
- Institute of Materials Science (IMT), Friedrich-Schiller-University Jena, D-07743 Jena, Germany
Rafael Y. Ballester
- Department of Dental Materials, School of Dentistry, University of São Paulo, São Paulo, Brazil

Received 18 September 2010; received in revised form 30 September 2011; accepted 1 October 2011.

Abstract

Objectives

The C-Factor has been used widely to rationalize the changes in shrinkage stress occurring at the tooth/resin-composite interfaces. Experimentally, such stresses have been measured in a uniaxial direction between opposed parallel walls. The situation of adjoining cavity walls has been neglected. The aim was to investigate the hypothesis that: within stylized model rectangular cavities of constant volume and wall thickness, the interfacial shrinkage-stress at the adjoining cavity walls increases steadily as the C-Factor increases.

Methods

Eight 3D-FEM restored Class I ‘rectangular cavity’ models were created by MSC.PATRAN/MSC.Marc, r2-2005 and subjected to 1% of shrinkage, while maintaining constant both the volume (20mm³) and the wall thickness (2mm), but varying the C-Factor (1.9–13.5). An adhesive contact between the composite and the teeth was incorporated. Polymerization shrinkage was simulated by analogy with thermal contraction. Principal stresses and strains were calculated. Peak values of maximum principal (MP) and maximum shear (MS) stresses from the different walls were displayed graphically as a function of C-Factor. The stress-peak association with C-Factor was evaluated by the Pearson correlation between the stress peak and the C-Factor.

Results

The hypothesis was rejected: there was no clear increase of stress-peaks with C-Factor. The stress-peaks particularly expressed as MP and MS varied only slightly with increasing C-Factor. Lower stress-peaks were present at the pulpal floor in comparison to the stress at the axial walls. In general, MP and MS were similar when the axial wall dimensions were similar. The Pearson coefficient only expressed associations for the maximum principal stress at the ZX wall and the Z axis.