Mechanical tests of smooth silver-plated retention pins in amalgam

Retention and stress concentration factors can be improved if a good mechanical bond exists between smooth retention pins and an amalgam restoration. It is shown that, by silver-plating pins and by using a rubbing technique during condensation of the amalgam, a good mechanical bond is produced. Mechanical tests of this bond show that its shear strength is adequate to withstand the stresses likely to be produced by occlusal forces. The form of the tests was: (a) torsion, to demonstrate the performance of the bond in shear and (b) push-through, to provide stress distributions more closely allied to those found under clinical conditions. Plain stainless steel and plated stainless steel pins were compared for their performance and sterling silver pins were used for checking the validity of the torsion test methods. It is concluded from these tests that, with the plating and "rubbing" techniques mentioned, a good mechanical bond is produced which is likely to have value in clinical dentistry.