Technique tips – management of a precision attachment crown fractured at gingival level

Extra-coronal precision attachments can help retain removable partial dentures and can avoid the need for visible clasps.1 There are a number of different attachments in use and, in this particular case, a Mini-SG®F2 was used to help retain a removable partial denture (Figure 1). The male attachment was incorporated into a porcelain fused-to-metal crown, and the female portion into the partial denture (Figure 2). Both functioned well for nine years but then the crown fractured off at the gingival margin. Some caries was noted in the remaining root. The options available in this situation are limited as there was no supragingival tooth onto which the crown could be cemented. If the tooth was to be retained, then a root-filling would be necessary, followed by a post-retained core. The crown would then have to be re-cemented in exactly the same position, otherwise the precision attachment would not align with the RPD. The patient was keen not to lose the attachment as it has functioned so well.

The solution was to reposition the tooth temporarily onto the root, ensuring that the denture would still fit, and then to make a GC Pattern Resin3 jig which would help position the tooth later (Figure 3).

The crown was then removed and the tooth tissue removed from inside the crown.

Root canal treatment was completed and two fibre posts cemented with Rely X Unicem(3M ESPE, St Paul, Minn, USA) (Figure 4).

A composite core was built up on the posts and root face and prepared, allowing the crown to fit over the core. Because the profile of the root face had changed, the jig would be necessary to cement the crown in exactly the same place as it was prior to breaking, thus allowing the correct fit of the RPD. The crown was placed into the jig and then cemented onto the core with Rely X Unicem. Owing to the slight discrepancy in the shape of the root face after the caries removal and root canal treatment, some of the lute filled this defect. Any excess cement was then trimmed away with a fine diamond finishing bur and polished (Figures 5 and 6). The long-term prognosis of this restoration will be in doubt as there was no ferrule, but it remains in function six months later.