Improved retention of acid-etched fixed partial dentures: a longitudinal study.

Debonding of acid-etched fixed partial dentures has been a problem since their introduction. A study was conducted to determine whether this problem could be resolved by modifying the mechanical retention of tooth preparations. Retentive grooves were prepared at the line angles to create mechanical locks for the resin bonded fixed partial denture. The 4-year retention of posterior resin-bonded fixed partial dentures improved from 60% to 95% by the placement of the proximal grooves. This study was conducted in a dental school clinic during a period of 10 to 52 months. The results demonstrated that design modifications were necessary to improve clinical longevity so that the restoration could be considered "permanent" in the traditional sense. The less-experienced dentist may be more confident of the treatment with the recommended modifications and projected longevity.