Self-threading pin penetration into dentin.

A laboratory study has shown that the first-half of self-shearing 2-in-1 self-threading pins, sizes 0.031 inch and 0.024 inch, fail to reach full channel depth when placed with either a hand wrench or an Auto Klutch handpiece. The average discrepancy of penetration is about 0.75 mm. This discrepancy in seating results in a significant excess pin length extending into the tooth preparation, which compromises the strength characteristics of the amalgam restoration.