Six-year clinical evaluation of bonded and pin-retained complex amalgam restorations

This clinical study compared the performance of complex amalgam restorations retained with self-threading pins or bonded with a filled, 4-META-based resin. Sixty amalgam restorations (28 pin-retained and 32 bonded), each replacing at least one cusp, were placed. Self-threading stainless steel pins (Coltene-Whaledent) were used in the pin-retained group. A filled, 4-META-based bonding resin (Amalgambond Plus with HPA powder) was used in the bonded group. For both groups, any retention form remaining after removal of an old restoration was left in place but not enhanced. At six years, 11 restorations had failed; eight of which were pin-retained and three bonded. Using Fisher's exact test to compare the groups at six years, there was no significant difference in failure rate, marginal adaptation, marginal discoloration, secondary caries, tooth sensitivity or tooth vitality. At six years, there was no difference in the performance of pin-retained amalgam restorations and bonded amalgam restorations.