Parameters affecting retentive force of electroformed double-crown systems

Area of Science:

• Dental Materials Science
• Prosthodontics
• Biomaterials Engineering

Background:

• Double crowns are widely used in removable partial dentures.
• Understanding the retentive forces is crucial for clinical success and patient comfort.
• Factors like abutment height, material, and taper can affect the performance of double crowns.

Purpose of the Study:

• To quantify the retentive forces of double crowns.
• To evaluate the influence of abutment height, inner crown material, and taper on these forces.

Main Methods:

• Sixty inner crowns each of zirconia and gold alloy were fabricated with varying abutment heights (5, 7, 9 mm) and tapers (0°, 2°).
• Outer crowns were produced using an electroforming system.
• Removal tests were conducted using a universal testing machine, with ten separation cycles per specimen.

Main Results:

• Retention forces ranged from 0.37 to 2.65 N.
• Abutment height (p < 0.001), material (p = 0.035), and taper (p < 0.001) significantly impacted retention.
• Zirconia showed superior performance over gold alloy in the 0° taper group, particularly with short abutments.

Conclusions:

• Abutment height, inner crown material, and taper are critical factors influencing double crown retention.
• Zirconia presents a viable alternative to gold alloy for primary crowns, especially with a 2° taper and long abutments.
• Clinical implications of 0° taper and short abutments require further investigation.