Objectives: This study was carried out to verify that changing the point of attachment of the connector onto the retainer wing can potentially improve the retention of a cantilevered resin bonded bridge in the anterior dentition and that retention was independent of bonding area.

Methods: Tensile peel forces required to debond a Ni/Cr beam from a block of the same material were measured for forces applied in two directions, simulating labio lingual and occlusal forces. Subsequently, beams with an altered point of attachment were tested. Two finite element analysis (FEA) models, one simulating the original design and the other simulating the new design were created, loaded and the stress patterns examined.

Results: When labio lingual forces were applied there was no statistically significant decrease in retention (p > 0.05) as the surface area of bonding was reduced. When occlusal forces were considered, the decrease in retention became statistically significant (p < 0.05) when the surface area of bonding was reduced below 5 sq.mm. Additionally the occlusal forces required to debond the beam were about 10 times greater than the labio lingual forces required for the same beam. In the FEA of the original design labio lingual forces developed a stress concentration in the adhesive layer within the first 0.5 mm of bonding. The rest of the bonded area made virtually no contribution to the dissipation of stresses. In the FEA of the new design, no stress concentrations were noticed and the stresses were about three times lower.

Conclusions: 1. Labio lingual forces play a more important role in the debonding of an anterior cantilever resin bonded bridge than occlusal forces and are independent of the surface area of bonding. 2. Altering the point of attachment of the connector can potentially improve the retention of an anterior cantilever resin bonded bridge.

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