A comparison of pin-retained amalgam and composite resin cores.

The 24 hour tensile loads required to separate the core material and dentin produced the following results: 1. No statistical difference was found between the tensile strength of retained amalgam and composite resin core materials. 2. Generally, no statistical difference was found between the retentive ability of three and four pins. 3. No statistical difference was found between the retentive ability of regular pins and minim pins if three or more pins were employed. 4. As the number of regular pins was increased beyond three, and when four minim pins were used, there was a very significant increase in dentin fracture.