Assessing the effect of testing variables on measured adhesive bond values
Date
2007
DOI
Authors
Al-Badawi, Emad AbdulRahman I
Version
OA Version
Citation
Abstract
Statement of problem: Published adhesive bond studies exhibit a wide variance of bond strength values which may be attributed to differences in testing methodologies.
Purpose: To determine the effect of different testing methodologies for dentin adhesives by comparing the following variables: shear vs. microtensile loading, loading apparatus geometry, specimen diameter and dentin surface preparation method.
Methods: Optibond Solo Plus (Kerr), Optibond FL (Kerr) and Adper Prompt (3M-ESPE) were used to bond composite resin (Z100, 3M-ESPE) to dentin. For shear mode testing the occlusal surfaces of human molars were sectioned to the dentin surfaces. Flat surface preparation was performed by diamond grit disc # 70, 45 and 15 micron in succession. Using a split mold, composite cylinders of 1, 2 and 4mm diameter (n=15/group) were bonded to the dentin surfaces. Bond strength was tested at 24 hrs in shear mode using a wire loop, knife blade, flat blade, notched blade and flat blade-on-iris, at 0.5 mm/min (Instron). In addition, 2mm composite specimens were bonded to dentin surfaces prepared by a diamond bur, using all 3 adhesives (n=15/group). These specimens were tested in shear mode using the flat blade. For microtensile testing mode the flat dentin occlusal surfaces were prepared by a #55 carbide bur. The adhesives were applied as previously and composite was added to the entire surface by incremental layers (Z1OO, 3M-ESPE) to a height of 6mm. Each restored tooth with the composite build-up was sectioned into four rectangular bars. Dumbbell shape specimens (0.8mm diameter bonded area) were formed in a "specimen former" machine. Tensile bond strength was tested (n=20/group for OptiBond Solo Plus and OptiBond FL, n=7/group for Adper Prompt) at 24 hrs (Zwick testing machine). ANOVA and Tukey multiple comparison tests were used for data analysis (P[less than]0.05). An independent T-Test was used to evaluate the effect of different dentin surface preparations.
A Photoelastic model was formed to resemble the bonding configuration for the shear test with identical testing setups. The model was shear loaded in an Instron machine and the resulting stress patterns were photographed. In addition, a three-dimension finite element analysis computer model was constructed to mimic the shear and microtensile tests geometries and loading conditions.
Results: The knife and wire loop produced significantly lower bond strengths than the flat, notched and flat-on-iris methods, which did not differ significantly. The 1mm samples produced significantly higher bond strengths than 2 and 4mm samples. There was no significant difference between the two dentin surface preparation methods. The microtensile test exhibited larger measured bond strengths than the shear tests. The photoelastic analysis demonstrated higher stress concentration with the knife and wire loop load geometries, while the flat, notched and flat-on-iris methods exhibited similar stress distributions. The finite element stress analysis revealed different stress distribution patterns for different loading geometries. Uniform stress distribution was observed in the flat-on-iris while the highest stress concentration was found at the load application of the knife blade.
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Description
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Thesis (D.Sc.D.)--Boston University, Goldman School of Dental Medicine, 2007 (Dept. of Restorative Sciences and Biomaterials).
Includes bibliographical references: leaves 190-205.
Thesis (D.Sc.D.)--Boston University, Goldman School of Dental Medicine, 2007 (Dept. of Restorative Sciences and Biomaterials).
Includes bibliographical references: leaves 190-205.
License
This work is protected by copyright. Downloading is restricted to the BU community. If you are the author of this work and would like to make it publicly available, please contact open-help@bu.edu.