Shear bond strength in porcelain-metal restorations

Area of Science:

• Materials Science
• Dental Materials Science
• Biomaterials Engineering

Background:

• Accurate measurement of shear bond strength is crucial for dental materials.
• Previous testing methods may not accurately reflect true shear bond strength under clinical conditions.
• Understanding bond strength between dental stone and metal, and porcelain to gold alloys is essential.

Purpose of the Study:

• To compare the shear bond strength values obtained from push and pull test methods.
• To evaluate the validity of the waxed-rod test for determining true shear bond strength.
• To report shear bond strengths for specific dental material combinations.

Main Methods:

• Comparison of push test and pull test methodologies for shear bond strength assessment.
• Utilizing a waxed-rod test to eliminate confounding factors and assess true shear bond strength.
• Testing bond strength between dental stone and metal rods, and Ceramco porcelain fused to Ceramco gold.

Main Results:

• Push test methods consistently demonstrated higher shear bond strength values compared to pull tests.
• A bond strength range of 4,500 to 6,000 psi between dental stone and metal rods was invalidated by the waxed-rod test.
• The waxed-rod test, despite yielding lower values, is considered a more accurate measure of shear bond strength.
• Shear bond strengths of 12,000 psi (push) and 9,700 psi (pull) were recorded for Ceramco porcelain fused to Ceramco gold.

Conclusions:

• The push test method appears to overestimate shear bond strength compared to the pull test.
• The waxed-rod test provides a more reliable assessment of true shear bond strength for dental materials.
• Specific shear bond strength values for Ceramco porcelain to gold alloys were established, with push tests indicating higher values.