Influence of joint component mechanical properties and adhesive layer thickness on stress distribution in micro-tensile bond strength specimens

Neves, Aline de A.; Coutinho, Eduardo; Poitevin, André; Van der Sloten, Jos; Van Meerbeek, Bart; Van Oosterwyck, Hans

doi:10.1016/j.dental.2008.04.009

« Previous Next »Dental Materials
Volume 25, Issue 1 , Pages 4-12, January 2009

Influence of joint component mechanical properties and adhesive layer thickness on stress distribution in micro-tensile bond strength specimens

Aline de A. Neves
- Katholieke Universiteit Leuven, Department of Conservative Dentistry, Leuven BIOMAT Research Cluster, Belgium
Eduardo Coutinho
- Katholieke Universiteit Leuven, Department of Conservative Dentistry, Leuven BIOMAT Research Cluster, Belgium
André Poitevin
- Katholieke Universiteit Leuven, Department of Conservative Dentistry, Leuven BIOMAT Research Cluster, Belgium
Jos Van der Sloten
- Katholieke Universiteit Leuven, Department of Mechanical Engineering, Division of Biomechanics and Engineering Design, Belgium
Bart Van Meerbeek
- Katholieke Universiteit Leuven, Department of Conservative Dentistry, Leuven BIOMAT Research Cluster, Belgium
- Corresponding author at: Katholieke Universiteit Leuven, Department of Conservative Dentistry, Leuven BIOMAT Research Cluster, Kapucijnenvoer 7, 3000 Leuven, Belgium. Tel.: +32 16 337587; fax: +32 16 332752.
Hans Van Oosterwyck
- Katholieke Universiteit Leuven, Department of Mechanical Engineering, Division of Biomechanics and Engineering Design, Belgium

Received 15 October 2007; received in revised form 20 March 2008; accepted 15 April 2008.

Abstract

Objectives

Differences in mechanical properties between adherents and adhesive result in stress singularity at the free edge for tensile test specimens. Beyond causing premature failures, these also trigger fracture initiation at the bond edge, where the use of the maximum stress at failure as a measure of strength is not a reliable parameter for obtaining bond strength. The aim of this study is to describe the pattern of stress concentration along the interface for micro-tensile bond strength (μTBS) specimens. Also, possible sources of variation in stress concentration (adhesive layer thickness and mechanical properties) were evaluated using the finite element method.

Methods

One-fourth models of typical μTBS specimens were created using axisymmetric elements. A 15MPa load was applied at the outer edge and finite element calculations were performed within the elastic deformation range. In the first set of runs, the adhesive thickness was varied and in the second set, different ν/E ratios between the adhesive and the adherent were assigned.

Results

When adhesive thickness increased, a significant increase in stress concentration at the free edge and in the length of the stress-affected area was observed. Increasing the ν/E ratio between adhesive and adherent lead to an increase in stress concentration at the free edge area without change in length of the stress-affected area.

Significance

If mechanical properties and adhesive thickness expected for a specific composite–dentin bond combination in μTBS specimens are known, stress concentration at the interface can be predicted. The adhesive thickness should remain constant when comparing different joints, as it facilitates the interpretation of nominal strength values.

Keywords: Micro-tensile bond strength test, Composite–dentin interface, Micro-specimens, Stress concentration, Adhesive bond, Stress singularity