The performance of bonded vs. pin-retained complex amalgam restorations - A five-year clinical evaluation

Background. The authors compared the clinical performance of complex amalga m restorations, replacing at least one cusp-retained either mechanically wi th self-threading pins or bonded-with a filled, 4-methacryloxyethyl trimell iate anhydride, or 4-META, -based resin designed for amalgam bonding. Methods. The authors placed 60 amalgam restorations (28 pin-retained and 32 bonded), each restoration replacing at least one cusp. They used self-thre ading stainless steel pins in the pin-retained group and a filled, 4-META-b ased bonding resin in the bonded group. For both groups, the authors left i n place any retention form remaining after removal of an old restoration bu t did not enhance it. Results. At four years, six restorations had failed. At five years, of the 40 restorations available for evaluation, three had failed, for a total of nine failed restorations; seven of those were pin-retained and two were bon ded. Using the Fisher exact test to compare the groups at five years, the a uthors found no significant difference in failure rate, marginal adaptation , marginal discoloration, secondary caries, tooth sensitivity or tooth vita lity. Conclusions. At five years, there was no difference in the performance of p in-retained amalgam restorations and bonded amalgam restorations. This stud y will be continued for at least a sixth year. Clinical Implications. Bonding with a filled, 4-META-based bonding resin ap pears to be a satisfactory method of retaining large amalgam restorations r eplacing cusps.