Retention and resistance provided by nine self-threading pins.

Extracted molar teeth, reduced to a flat surface approximately 3 mm coronal to the cementoenamel junction, were notched and embedded in acrylic. Nine types of pins were tested for retention in dentin and for resistance provided to complex amalgam restorations. Pins of each type were inserted into dentin and removed in tension with a constant load applied by an Instron Testing Machine (six pins per tooth). Minim and PPS pins provided significantly better retention in dentin than the other pins. Pins of each type were inserted into flattened teeth. Amalgam was condensed around the pins, allowed to set, and loaded in compression at 45 degrees. Pure titanium pins and heat-softened stainless steel pins provided significantly less resistance than titanium alloy or stainless steel pins.