Amalgam buildups: shear strength and dentin sealing properties

Area of Science:

• Dental Materials Science
• Restorative Dentistry

Background:

• Amalgam restorations are widely used in dentistry.
• Effective retention and sealing are crucial for the longevity of amalgam buildups.
• Minim pins, circumferential slots, and adhesive resins are methods to enhance amalgam retention.

Purpose of the Study:

• To compare the retentive strength and dentin sealing properties of amalgam buildups retained by Minim pins, circumferential slots, or adhesive resin.
• To evaluate the effect of thermocycling on dentin permeability after amalgam buildup placement.

Main Methods:

• Three groups of extracted teeth with flat, nonretentive surfaces were prepared.
• Group 1: Amalgam retained by four self-threading Minim pins.
• Group 2: Amalgam retained by a circumferential slot in dentin.
• Group 3: Amalgam retained by adhesive resin.
• Dentin permeability was measured as hydraulic conductance before and after buildup placement and thermocycling.

Main Results:

• All retention methods effectively sealed dentin, even without cavity varnish.
• The 90-degree retentive strength was significantly higher for Minim pins (10.3 MPa) compared to slots (4.1 MPa) and resin (3.1 MPa).
• Thermocycling did not significantly alter the sealing effectiveness of the tested methods.

Conclusions:

• Minim pins provide the highest retentive strength for amalgam buildups among the tested methods.
• Circumferential slots and adhesive resins offer lower retentive strength but still provide adequate dentin sealing.
• All evaluated retention techniques demonstrate promising sealing capabilities for amalgam restorations.