Adhesion to tooth structure: a critical review of "macro" test methods

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Mechanical Engineering

Background:

• Bond strength testing in dentistry is complex due to numerous variables, hindering study comparisons.
• Failure modes in bond strength tests often compromise results by extending into the tooth or composite.
• Despite the rise of micro-scale tests, macro-scale bond strength evaluations remain prevalent in research.

Purpose of the Study:

• To critically review specimen geometry and test mechanics in macro shear and tensile bond strength tests.
• To analyze the influence of various parameters on stress distribution at the bonded interface.
• To provide insights into the interpretation of bond strength test results.

Main Methods:

• Literature review of macro bond strength testing methodologies.
• Finite Element Analysis (FEA) to assess stress distribution under different parameters.
• Analysis of failure modes and their implications.

Main Results:

• Bond strength increases with smaller bonding areas and high elastic modulus composites.
• Shear tests exhibit more severe stress concentration than tensile tests, with chisel methods showing the highest.
• Crosshead speed within ISO/TS 11405 limits did not significantly affect bond strength.
• Pooled data revealed 44% adhesive, 31% mixed, and 25% cohesive failures.
• Macro tests showed similar material ranking to micro tests but a higher incidence of cohesive failures.

Conclusions:

• Macro bond strength tests remain popular due to their simplicity, despite inherent limitations.
• Understanding stress distribution and its influencing factors is crucial for accurate interpretation of bond strength test results.
• Mechanical analysis of test methods is essential for reliable dental material evaluation.