Effect of convergence angle on retention of resin-bonded retainers cemented with resinous cements

Statement of Problem. Poor retention is a common cause of failure for resin-bonded restorations. Purpose. This study evaluated the effect of the convergence angle of tooth preparations on retention of resin-bonded restorations, luted with adhesive and conventional resinous cements. Material and Methods. A total of 80 posterior retainers with four different tooth preparation angles were cemented with two different resinous cements, and retentive strength was measured. Results. The results indicated that (1) increased tapering of tooth preparations resulted in loss of retention and this variable was statistically significant for both cements used when convergence angles exceeded 10 degrees and (2) sandblasted nickel chromium retainers, combined with adhesive resins, should provide sufficient retention for posterior resin-bonded fixed partial dentures.