THE EFFECT OF THE MISMATCH BETWEEN THE CORE DIAMETER OF SELF-THREADING DENTIN PINS AND THE PINHOLE DIAMETER

This laboratory study incorporated the use of three different sized tw ist drills to prepare pinholes in extracted upper molar teeth. The dia meter of each pinhole was measured. A pre-measured self-threading pin was then placed in each pinhole. The amount of strain created during p in placement (placement strain), the temperature rise during pin place ment, the amount of strain remaining (residual strain) within the toot h structure after pin placement and the removal force (retention) were recorded for each pin. The results showed that, during the placement of a self-threading dentine pin, the difference between the pincore di ameter and the pinhole diameter was an important parameter. This diffe rence determined the amount of strain created during pin placement, th e temperature rise during pin placement, the amount of strain remainin g within the tooth structure after pin placement and the retention of the pin. The placement strain, temperature rise, residual strain and r etention were ail greater when the pin core diameter exceeded the pin hole diameter.