The slippery slope: critical perspectives on in vitro research methodologies

Area of Science:

• Biomaterials science
• Dental materials research
• Mechanical testing

Background:

• In vitro research is essential for evaluating dental materials.
• Existing methodologies like shear bond, wear, and load-to-failure tests are widely used.
• There is a growing need to ensure laboratory findings translate to clinical success.

Purpose of the Study:

• To critically evaluate common in vitro testing methodologies in dentistry.
• To assess the clinical validity of shear bond, wear, and load-to-failure tests.
• To propose improvements for in vitro tests to better simulate clinical conditions.

Main Methods:

• Analysis of published shear and tensile bond data using finite element analysis (FEA) and Weibull scaling.
• Re-examination of wear test results in relation to damage mechanisms and contact pressure.
• Re-analysis of load-to-failure test data by calculating contact stresses from 54 publications.

Main Results:

• FEA and Weibull analysis indicate failure origins are external surfaces, not interfacial shear stresses.
• Wear test results are significantly influenced by contact pressure, which is often poorly controlled.
• Load-to-failure tests generate clinically irrelevant damage due to excessively high contact stresses (1000-5000MPa vs. clinical <40MPa).

Conclusions:

• In vitro test designs require significant improvement to accurately simulate clinical conditions, particularly concerning contact mechanics.
• Journals should consider rejecting studies employing flawed bond and load-to-failure tests lacking clinical relevance.
• Enhanced validation of in vitro tests against clinical performance is necessary.