Apical transportation revisited or 'where did the K-file go'?

This case report describes the outcome of a number of retreatments on a failed root filling in a maxillary first molar. The patient wanted all amalgams replaced by tooth-coloured Cerec restorations, including one in a symptomless maxillary molar. This tooth had a pulpotomy or a poorly done root-canal treatment 10 years earlier. The molar was root-canal retreated before placing the Cerec restoration and the palatal canal was filled 5 mm short of the radiographic apex. About 1 year later the patient presented with pain. Suspecting that a second mesiobuccal canal (MB-2) had not been located, a second non-surgical retreatment was instituted. MB-2 was not found and the palatal canal was retreated a third time, setting the working length 2 mm short of the radiographic apex. Because pain persisted palatally an apicectomy was performed and the tooth became symptomless. The resected palatal root apex was subsequently serially cross-sectioned, photographed and the canals analysed. Obvious apical transportation occurred during the cleaning and shaping procedures. Analyses of the canals showed that despite the retreatments, 11% of the canal cross-sectional area remained uncleaned although 7% of the root area was 'shaped'. Radiographically, the obturated palatal canal appeared reasonably well centred. However, this was disproved by the cross-sections, indicating that in this case, the clinician did not know where the K-Files had 'gone'. Apically, the obturated canal was certainly not within the natural canal. The pain located palatally was probably due to inadequate cleaning and shaping of the apical part of the root canal and its accessory canals.