A review of concepts of silver amalgam retention

Retention grooves and undercuts are not advantageous to an amalgam cavity preparation. These mechanical locks do not prevent fracture of the proximal portion in vivo, do not inhibit marginal fracture, are not necessary for retention, and are a factor in the split-tooth syndrome. The tensile stress needed to dislodge the restorations would be impossible to achieve in the oral environment, and therefore, additional retention is not worth the added risk of endangering the integrity of the tooth and the pulp. All factors considered, a properly prepared, conservative Class II Black's type of cavity preparation not only remains the easiest to prepare with conventional instrumentation but also is totally adequate to withstand the stresses of mastication, magnifying the desirable properties of the amalgam restoration.