Article
A year ago, when in the throes of moving from the old to the new dental school in Birmingham, I came across a paper that I had written in 1998. This described two identical twin sisters with missing lateral incisors, one who I had treated with conventional fixed bridgework, the other with (the then new) resin-bonded bridges (RBBs). In an editorial last year, I stated that, with the benefit of hindsight, I would have done things differently and both might have been better served by having RBBs. Life rarely stands still, so, just over a year on, there are a number of recent publications providing stronger evidence (either by including high numbers of bridges, or lengthy observation periods) than was available when I last addressed the subject. Let‧s take a look at these.
Mattias Kern1 has examined the performance of glass-infiltrated alumina ceramic cantilever RBBs. Twenty-two of these were provided for 16 patients who had one or more missing lateral incisor teeth (a much-used indication for RBBs), with the bridges being luted with Panavia 21 (Kuraray). The mean observation time was 188 months: the abutment preparation included a lingual veneer, a shallow cingulum groove and a small proximal box preparation. No bridges lost retention and the two failures were due to fracture of the alumina framework, giving an overall 10-year survival using Kaplan-Meier methodology of 95.4%. However, in a recent review of all-ceramic resin-retained bridges in Dental Update by Shah and Laverty,2 the authors concluded that the research that is currently available favours the use of metal RBBs.
The work of Botelho and colleagues3 is therefore of relevance. They reviewed 22 (of 28 recruited) patients who had received either a two-unit cantilevered or three-unit fixed-fixed metal-ceramic RBBs to replace a missing lateral incisor, with a mean service life of 216 months. All the cantilever bridges had functioned satisfactorily at this time, while only 10% of the three-unit bridges experienced no complications and only 50% survived. It was the authors' correct view that theirs was the only study which ‘clearly and unequivocally’ demonstrated the advantage of the cantilevered prosthesis over the fixed/fixed variety. This success is thought to be due to the differential movements of the abutment teeth that stresses the bonding interface in the fixed/fixed prosthesis.
A greater number of RBBs was provided in the study by Allen et al,4 but for a shorter time. In this, 40 patients received a total of 65 metal-ceramic, resin-retained bridges and, at 24 months, 63 were still in function, with the two bridges that failed because of repeated debonding being in posterior teeth. Twenty-two bridges replaced missing premolar teeth, the remainder replacing incisors. The anterior teeth received 0.5 mm proximal groove preparations and 1 mm palatal reduction and the posterior abutment teeth received an interproximal groove and rest seat preparations. The overall 24-month survival rate was 97%, with the authors concluding that the technique provided a reliable and acceptable treatment option in the medium term, but commenting that occlusal overload may be a factor in success of RBBs.
Finally, high on the scale of ‘evidence’ is a systematic review and meta-analysis, so the paper by Wei and co-workers5 is worth looking at. They screened 1010 articles but, as often is the way, the inclusion criteria only fitted one randomized controlled trial and four cohort studies, nevertheless including 213 RBBs. Their results indicated that cantilevered RBBs demonstrated lower clinical failure rates than two-retainer bridges in the anterior region. All-ceramic bridges showed a 10-year failure rate of 26% in the fixed/fixed group and only 5.6% in the cantilever group, with the authors concluding that fewer retainers is recommended.
I read recently that the RBB is a suitable temporary restoration while waiting for a mouth to mature sufficiently for implant placement in a young patient. Not the case! These recently published research papers indicate that the resin-retained bridge is no longer the Cinderella of dental crown and bridge and that they are here to stay (in more ways than one!), especially those with a cantilever design. In addition, readers of Dental Update have the advantage of being able to read the two excellent papers by Gulati and colleagues,6,7 describing the techniques which will help clinicians provide successful RBBs.