Factors influencing the retention of cemented implant-supported crowns

This study is a retrospective analysis of the influence of cement, coping type, and fixture site on the cementation failure of 36 selected implant-supported single crowns placed between 1991 and 1995. Fisher's exact test and a log linear analysis were performed on the data. Crowns constructed with a milled-metal coping, cemented with a temporary cement, or placed in the maxillary premolar site were more likely to be associated with cement failure than those cemented with zinc phosphate, constructed with cast metal or ceramic copings, or placed in the anterior maxilla. We were unable to account for some variables-for example, bite force or oral habits. For this reason we consider that we would overstate the strength of this case analysis if we drew general conclusions from our results. However, we have altered our treatment protocol to reduce the initial cost and the maintenance associated with recementing implant-supported crowns, discontinuing the use of the milled-gold cylinder in view of the lack of any clear clinical advantage and the results of this study. In addition, and because only one internal gold screw in our series of patients has loosened, we now use a permanent cement.