A resin-retained bridge is a bridge (a fixed dental prosthesis) replacing a missing tooth that relies for its retention on a composite resin cement. It is one of many available dental restoration methods.
A resin-bonded bridge consists of a cast metal framework that is cemented with resin composite to an abutment(s) which has preparation(s) confined either entirely or almost entirely to enamel.
The resin-retained bridge is a good treatment option for many missing teeth as it is relatively cheap when compared to alternatives such as dental implants, requires little or no damage to the surrounding teeth during preparation for placement, and it is well tolerated by patients. Typical success rates are quoted as being as high as 80% after 15 years in the anterior maxilla. Far lower success rates are seen in the posterior mandible.
Thus case selection is important. As with any dentistry, good oral hygiene is paramount for success.
One major advantage of the resin-retained bridge over a conventional bridge is the failure mode is likely to be debonding of the retainer. In conventional bridges, the failure mode is likely to be complete fracture of the abutment tooth with difficult-to-manage sequelae, possibly requiring root canal treatment. With a resin-retained bridge the prosthesis can usually be cleaned off and rebonded in position with minimal inconvenience to the patient.
The resin-retained bridge has gone through a number of iterations. Perhaps the best known is the Maryland bridge. Other designs used in the past include the Rochette bridge.
A resin-retained bridge requires a very specific set of design principles.
The wing or retainer must be rigid and is usually fabricated from a metal alloy. The inner surface must fit closely to the abutment tooth. The intaglio is treated in some way to enhance the micromechanical adhesion between the prosthesis and the composite resin cement. In the past various methods have been used, ranging from metal-weave patterns to tin plating. The modern resin-retained bridge retaining wing is usually sandblasted with an alumina powder. The metal wing needs to engage as much of the sound enamel. In the majority of cases the metal wing is taken to the incisal edge of anterior teeth and overlapping of the occlusal (biting) surface of the teeth for posterior teeth.
The pontic is usually made from dental porcelain. The whole restoration is thus a porcelain fused to metal restoration.
Current cement brands commonly used for this procedure include Panavia and Nexus. All are either autocure or dual-cure to ensure complete polymerisation of the resin under the wing. Great care must be taken during cementation to avoid contamination of the operative field as this will lower the bond strength of the cement and lead to premature failure. For this reason rubber dam is often advocated for placement, though this can bring its own difficulties. In the majority of cases, with good four handed dentistry, rubber dam is not required and does not improve success.
The resin-retained bridge is increasingly being used in modern dentistry as an alternative to more destructive treatments. This has been driven by the advent of evidence-based dentistry showing the benefits to patients of reduced tooth preparation and the importance of an intact enamel structure for the long-term health of the teeth. The resin-retained bridge is currently in favour in the United Kingdom for these reasons. Indeed, recent contemporary research shows resin retained bridges have better success rates than implants.