Retention design for amalgam restorations: pins versus slots

Area of Science:

• Restorative Dentistry
• Dental Materials Science

Background:

• Retention methods for amalgam restorations, including pins and slots, have conflicting efficacy reports in existing literature.
• The influence of preparation outline form on the effectiveness of these retention methods is not well-established.

Purpose of the Study:

• To investigate whether the retention effectiveness of pins versus slots in amalgam restorations is influenced by the preparation's outline form.
• To compare the fracture resistance of amalgam restorations with pin versus slot retention across different preparation designs.

Main Methods:

• One hundred forty melamine teeth were prepared with three distinct outline forms based on cusp removal.
• Restorations were made using hand-condensed amalgam with either pin or slot retention and milled to a 30-degree occlusal angle.
• Fracture resistance was determined by applying a load to the milled occlusion using a stainless steel ball until failure occurred via an MTS machine.

Main Results:

• No statistically significant difference in fracture resistance was observed between pin and slot retention designs.
• The effectiveness of pin versus slot retention remained consistent across all three evaluated preparation outline forms.

Conclusions:

• Both pin and slot retention methods are equally effective for amalgam restorations, irrespective of the preparation outline form.
• Clinical decisions regarding retention methods for amalgam restorations may not need to be dictated by preparation outline complexity.