A multi-practice clinical study on posterior resin-bonded bridges: a 2.5-year interim report.

A clinical trial of 201 posterior resin-bonded bridges (PRBBs) was conducted partially in a University clinic and partially in general dental practices, for study of the influence of some experimental variables on the survival of these restorations. This report contains the results of an interim analysis which was done after 2.5 years' follow-up. No significant differences were found among the bonding systems used to adhere the PRBBs (Clearfil F2/etching, Panavia EX/sandblasting, and Microfill Pontic C/silicate-coating), or among the different preparation forms. PRBBs made in general dental practices were as retentive as those made in the University clinic. The "location" factor was found to be highly significant (p = 0.0001). The survival rates were 81% for maxillary PRBBs and 56% for mandibular PRBBs.