Cemented Pins: The in vitro Relationship between Retention and Retentive Area

The relationship between retention and retentive area of cemented roughened pins was studied by varying the diameter and the length of pin holes drilled in PMMA plates. The retention of cemented pins was measured by a pull parallel to the pin axis. The roughness of a representative number of pin hole walls was studied by scanning electron microscopy after axial sectioning of the holes. Failure of the cement bond occurred at the cement-pin hole interface so that calculation of the retentive area was based on the diameter and the length of the pin hole. The results showed a high correlation between retention and retentive area, and that surface roughness of the pin hole walls may contribute strongly to the retention.