The effect of the mismatch between the core diameter of self-threading dentine pins and the pinhole diameter.

This laboratory study incorporated the use of three different sized twist drills to prepare pinholes in extracted upper molar teeth. The diameter of each pinhole was measured. A pre-measured self-threading pin was then placed in each pinhole. The amount of strain created during pin placement (placement strain), the temperature rise during pin placement, the amount of strain remaining (residual strain) within the tooth 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 diameter and the pinhole diameter was an important parameter. This difference determined the amount of strain created during pin placement, the temperature rise during pin placement, the amount of strain remaining within the tooth structure after pin placement and the retention of the pin. The placement strain, temperature rise, residual strain and retention were all greater when the pin core diameter exceeded the pin hole diameter.