Poor prognosis of posterior resin bonded adhesive bridges

Resin bonded adhesive bridges have been around for a long time. They were initially designed as temporary solutions for young patients who had a missing front anterior tooth. For these young patients, it was usually caused by an accident such as falling in the playground or a sports injury known as avulsion. Sometimes an anterior tooth would be congenitally missing, most often the lateral incisor.

A denture is not ideal for young patients hence the discovery of using a resin bonded adhesive bridge  with a view to being replaced with a more conventional fixed full coverage design once the pulp had regressed due to secondary dentine formation. Once the patient had passed their teens then a fixed bridge would be considered and planned.

However, it was accidentally found that many of these so-called temporary adhesive bridges would last a significant length of time and therefore dentists soon started to use these as a more permanent method of replacing a missing tooth. They obviously do have the advantage in being minimally invasive compared to other forms of fixed tooth replacements. Also initially they were only designed to replace lateral or missing central incisors. As dentists and researchers became more confident, it started to be used for posterior teeth including canines as well.

However the success rates in posterior teeth were not as good. Studies show that only 50% survived after 5-years.

Maxillary teeth seem to survive slightly longer than mandibular teeth.  This has been partially explained by mandibular teeth having less lingual surface area for coverage to bond onto.  Also, the ability to isolate into a dry field is much easier on upper teeth and flexing of the mandible is also thought to be a factor which increases debonding.

Perforations or the exact  cement used did not seem to make much difference to survival rates.

It was also shown that once a bridge de-bonded, it was more likely to come off repeatedly and therefore if a bridge keeps on the debonding, it is best for the patient and the dentist to decide on  either  replacing it altogether or using a different form of prosthesis altogether.

There was however one important factor that could influence the success rate of a posterior adhesive bridge. This was whether the tooth surface was prepared or not. This is in contrast to anterior bridges where no tooth preparation is needed even if the bridge is in premature occlusal contact as the occlusion re-adjusts and the patient adapts well.

If the tooth surface was prepared and there was a location factor such as using slots or grooves, the bridge would last longer. There are even advocates of using quite deep preparations and these are known as intra-enamel preparation designs.