Auxiliary retention for complete crowns provided by cement keys

Area of Science:

• Dental Materials Science
• Prosthodontics
• Biomaterials Engineering

Background:

• Complete cast gold crowns are widely used in restorative dentistry.
• Ensuring adequate retention of dental prostheses is crucial for long-term success.
• Factors influencing crown retention require continued investigation.

Purpose of the Study:

• To evaluate the effectiveness of cement keys in enhancing the retention of complete cast gold crowns.
• To compare the retentive strength of crowns with different taper angles (7-degree vs. 30-degree).
• To assess the impact of single grooves in dentin or crown on retention.

Main Methods:

• Complete cast gold crowns were prepared on extracted teeth.
• Cement keys were incorporated into some crown preparations.
• Single retention grooves were placed in dentin or crown for specific groups.
• Retentive strengths of crowns were measured under tensile load.
• Crowns with 7-degree and 30-degree taper angles were compared.

Main Results:

• Cement keys significantly increased the retention of complete cast gold crowns.
• Single grooves alone did not effectively increase retention in 30-degree crowns.
• In 7-degree crowns, a groove in the crown provided better retention than a groove in dentin.
• Crowns with a 7-degree taper exhibited greater retentive strength than 30-degree crowns.
• The retentive strength of 7-degree crowns with cement keys approached the tensile strength of zinc phosphate cement.

Conclusions:

• Cement keys are an effective method for improving complete cast gold crown retention.
• A 7-degree taper angle offers superior retention compared to a 30-degree angle.
• Optimizing crown preparation design, including taper and retention features, is vital for prosthetic stability.