The effects of bonding agents and retention grooves on the retention of approximal slot amalgam restorations


The retention of approximal slot amalgam restoration was measured in this in vitro study. Two bonding systems (All-Bond 2 and Scotchbond Multi Purpose Plus) in addition to Copalite varnish (as a control liner) were used as lining materials and compared in non–retentive and retentive approximal slot cavities using spherical and lathe cut alloys. Signifi-cantly higher retention values obtained with the retentive cavities. No significant difference was found between spherical and lathe cut alloys. Retention of the bon-ded restorations was significantly more than that of non–bonded groups, with All-Bond 2 was significantly more retentive than Scotchbond Multi Purpose Plus. Non-retentive cavity with varnish was the least retentive group while retentive cavity with All–Bond 2 was significantly more reten-tive than all other groups. When the rest-orations were bonded to the tooth, modes of failure were shifted toward mixed type (adhesive + cohesive failure) rather than complete dislodgment from the cavity. The results of this study indicated that bonding agents can be used to enhance the retention of amalgam restoration instead of the traditional mechanical retention means thus conserving the sound tooth structure. Also, the combination of mechanical ret-ention means and bonding agents has an additive retentive effect.