Abstract
BACKGROUND: The present study aimed to assess the internal root canal morphology and the quality of obturation in endodontically treated and failed first molars using micro-computed tomography (micro-CT). METHODS: Forty-three mesial roots of extracted first molars with failed endodontic treatment were examined using micro-CT to evaluate root canal filling quality and root canal and isthmus configurations. The presence of untreated missed canals and the length of the root canal fillings were assessed. The percentage of voids within the canal filling in both apical and coronal regions was compared using an independent samples t-test. Statistical significance was set at p < 0.05. RESULTS: An untreated second mesiobuccal canal was identified in 70.6% (n = 12) of the examined maxillary first molars, while a middle mesial canal was detected in 50.0% (n = 13) of the mandibular first molars. A significantly higher mean percentage of voids within the canal filling was observed in the apical region (15.3%) compared to the coronal region (7.3%) (p < 0.05). Short root canal fillings were observed in 57.7% of mandibular teeth and in 35.3% of maxillary teeth. CONCLUSIONS: The failure of endodontically treated teeth was associated with poor root canal filling quality and the presence of untreated extra canals, as revealed by micro-CT.