Microtensile bond strength tests: scanning electron microscopy evaluation of sample integrity before testing.

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Adhesion Science

Background:

• Microtensile bond strength (MTBS) testing is widely used to evaluate adhesive performance in dentistry.
• Premature failure of specimens during preparation or handling is a significant challenge in MTBS testing.
• Understanding the structural integrity of specimens is crucial for reliable adhesion assessment.

Purpose of the Study:

• To investigate structural defects in enamel and dentin microtensile specimens using scanning electron microscopy (SEM).
• To identify potential causes of premature specimen failure during MTBS testing.
• To evaluate the reliability of the MTBS method for assessing adhesion to enamel.

Main Methods:

• Preparation of 80 microtensile specimens from enamel and dentin substrates.
• Examination of specimen surfaces and interfaces using a scanning electron microscope (SEM).
• Qualitative analysis of observed defects, including microcracks, gaps, and voids.

Main Results:

• No specimens were found to be completely free of defects.
• Common defects included microcracks in enamel and at the hybrid layer in dentin.
• Gaps at substrate interfaces and voids within resin composites were frequently observed.
• Enamel specimens exhibited a higher prevalence of defects compared to dentin specimens.

Conclusions:

• Structural defects are inherent in microtensile specimens, potentially compromising test results.
• The brittleness of enamel may contribute to its higher defect rate and susceptibility to failure.
• The reliability of the MTBS method for evaluating enamel adhesion warrants further investigation.
• Developing methods for quantitative assessment of specimen integrity before testing is recommended.