Dentin bonding system. Part II: Effect of crosshead speed

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Mechanical Testing

Background:

• Dentin bond strengths are typically assessed using mechanical tests (tensile/shear) at varying crosshead speeds.
• Commonly used speeds range from 0.1 to 10.0 mm/min, but the rationale for selection is often absent in literature.
• Optimal testing conditions aim to induce fracture without plastic deformation.

Purpose of the Study:

• To investigate the influence of crosshead speed on dentin bond strengths.
• To determine the strain rate sensitivity of dentin bond strengths.
• To elucidate the mechanical behavior of the bonding interface during tensile testing.

Main Methods:

• Tensile bond strengths were evaluated using the Scotchbond Multiple-Purpose/Z100 bonding system.
• Testing was performed across a range of crosshead speeds: 0.1, 0.5, 1.0, 5.0, and 10.0 mm/min.
• Analysis focused on identifying strain rate dependency in bond strength measurements.

Main Results:

• No significant strain rate sensitivity was observed when testing below a crosshead speed of 1.0 mm/min.
• Tensile bond strengths exhibited a clear strain rate dependency when the crosshead speed exceeded 1.0 mm/min.
• The composite resin (Z100) itself did not show strain rate dependency.

Conclusions:

• The observed strain rate dependency in tensile bond strength is primarily attributed to the mechanical response of the bonding interface.
• Crosshead speed selection is critical for accurate dentin bond strength evaluation, particularly to avoid interface-dependent artifacts.
• Understanding strain rate effects is crucial for reliable assessment of dental adhesive performance.