Case• 35. A failed bridge
A 40-year-old man has a missing upper incisor replaced by a spring cantilever bridge. This has become decemented and you must assess options for replacement.
The patient complains that his anterior bridge has become detached. He would like it recemented or replaced.
History of complaint
The bridge had been satisfactory for many years but detached about 2 years ago. It was recemented and had been firm until yesterday when it fell off the teeth without warning.
The upper left central incisor had been lost as a result of a bicycle accident when the patient was aged 16. It was completely avulsed and the adjacent upper right central incisor was fractured. The missing central incisor was initially replaced with a simple spoon denture and then a few years later by a spring cantilever bridge attached to full coverage crowns on the left first and second premolars. The other upper central incisor was root treated and a post crown fitted. The present bridge is a replacement made about 8 years ago after the cantilever spring fractured. The patient has never had an upper left lateral incisor.
The dentition is in good condition with few carious lesions and a small number of restorations. The upper left premolars are the abutment teeth and have relatively conservative crown preparations. There is superficial caries over much of the surface of the first premolar crown and a larger cavity at the distal gingival margin. The mesial surface of the second premolar is also slightly carious. Both abutment teeth are vital. The gingival condition is good except for bleeding on probing between the abutment premolars. Here the probing depth is 4mm. The bridge can be replaced and the appearance with it fully seated is shown in Figure 35.1. The caries in the first premolar is exposed below the crown margin.
▪ What is the prognosis for this bridge? Why?
Hopeless. Figure 35.1 shows that the cosmetic result is not good. The bridge pontic has moved buccally and upwards, probably a combined result of alveolar ridge resorption and distortion of the spring cantilever. It also appears to have moved distally increasing the median diastema. The abutment teeth will both require re-restoration and the first premolar appears to be very carious. In the long term, both abutment teeth are compromised by the risk of further caries and periodontitis.
▪ Why was this method of replacing the central incisor chosen originally?
Although a well-designed partial denture should not compromise the health of the remaining dentition, most patients prefer a fixed prosthesis without palatal coverage for a single tooth replacement.
The spring cantilever design was considered suitable for this case for the following reasons.
• It allows diastemas between adjacent crowns. Diastemas would have been present because the lateral incisor on that side was developmentally absent. A replacement crown which filled the available space would be too wide.
• The upper right central incisor was not a suitable abutment tooth for conventional fixed bridgework, having been traumatized, root-filled and post-crowned using a prefabricated post.
▪ What replacement restorations would you consider? Explain your choices.
A new spring cantilever bridge. For the reasons noted above, the spring cantilever design remains a good choice and it has served this patient fairly well. However, the abutment teeth will require restoration and a further spring cantilever bridge may compromise the abutment teeth in the medium to long term.
An adhesive bridge could be supported on the upper left canine with the central incisor replaced by a cantilevered pontic. This would be possible because the lateral incisor is missing but would not normally be practical in this situation. This alternative has the advantage of minimal tooth preparation and allows maintenance of one diastema between the central incisors. However, success would be somewhat unpredictable, depending on the area of enamel available on the palatal aspect of the canine for bonding and the occlusal relationship. This might be considered the ideal medium term or provisional restoration. It also has the advantage that the existing abutment teeth could be rest/>