Comparison of the shear strength of pin retained and resin bonded amalgam cores

Abstract

Although amalgam does not adhere to tooth structure it is the most commonly used restorative material in dentistry. Undercutting is the most common method whereby retention is achieved for amalgam restorations but, because of amalgam's lack of adhesion, it is often necessary to make supplemental grooves and/or place retentive pins. It is to be noted that added in the laudable effort to reduce microleakage and strengthen the relationship between amalgam and dentin, resin bonded amalgam has been introduced. This innovation provides a technique whereby unfilled composite resin is bonded to the dentin, and amalgam is bonded to the resin producing thereby a composite/resin amalgam which has adhesive properties and reduced microleakage (Chang, 1992; Tjan, 1992; Scherman, 1990; Edgren, 1992). In a clinical setting, excessive tooth structure is often removed to improve retention in the preparation of extensively decayed teeth. This obviously weakens the supporting tooth structure at the expense of healthy tooth structure. On the other hand, retention of the restoration may be compromised in the effort to preserve tooth structure. If indeed resin bonding increases the retention of amalgam restorations, pins may no longer be needed, or they may be used in conjunction with resin bonding techniques in order to gain more strength than either technique alone. The purpose of this study is to evaluate and compare the retention of resin bonded amalgam with and without pins.