I answered an e-mail this evening about resin bonded bridges to replace maxillary lateral incisors. The patient is a 15 year old with congenitally missing laterals and the question is what to do in the interim to hold space, correct the esthetics, and create a situation where the patient can be comfortable and confident until she is older and can consider implant placement. Resin bonded bridges can be a great restorative option for young people as an medium term solution. The original design of resin bonded bridges required the preparation of the lingual of the abutment teeth and the framework was made from cast metal. The challenge of this classic design is that you can often see the shadowing behind the retainer tooth from the metal and at the connectors. Another more modern alternative I hear discussed is Zirconia. This approach has two major issues, one of which is the connector size, and it very rarely looks good or works with laterals. Both metal and zirconia have to be cemented as they can not be truly “bonded” for retention, which means you need some sort of prep and need to have light to no occlusion on the bridge. Even with this when you look at the research the classic de-bond of these bridges is between the restoration and the resin cement, not a failure of the bond to enamel.
Lithium Disilicate (e.max) is probably my first line of defense for these kind of bridges now. They can have normal size connectors and can be bonded with light cure resin cements and get bond strengths of 25-40Mpa. The amount of lingual tooth preparation is dependent on the occlusal clearance and can be as minimal as simply creating margins for the lab to fabricate to. In addition to looking at the bond failures over the years we have made the correlation between the number of abutments and the failure of these bridges. This research supports debonding of the retainers due to stress from flex and torque. In recent years it has become more popular to engineer these bridges as a cantilever so that you will reduce these stresses and minimize the number of failures due to the retainers detaching. So use the canines alone or the centrals alone as the abutments. Which teeth to select as the abutments is based on mapping the functional occlusion.
The functional risk of the case is an important factor to consider. These prostheses are very successful in patients who present without evidence of wear, joint or muscle issues that relate to occlusal concerns. I do them in this exact situation, and simply present it to the patient and parents as a long term provisional that we will bond a number of times between seat and when we replace it. I make my patients an essex retainer over the final bridge as an emergency solution. If the bridge debonds they can seat the pontic in the essex and wear it until we can get them in and bond it back in place. I make sure they take the essex even on vacation.