Abstract : One of the most commom variations of the normal state that cause difficulty for dental clinicians is the C-shaped canal in mandibular second molars. The present study was carried out in order to make a more accurate assessment of the status of the apical canal and supporting tissues in a tooth with marked periodontal lesion using radiographic, micro CT and histological techniques. The tooth concerned was an endodontically treated mandibular second molar with gutter shaped root. The patient was a 65-year-old Japanese male who had received pulpectomy approximately 27 years previously at another university. The tooth had been followed by canal obturation with gutta-percha points and zinc oxide eugenol sealer using a lateral condensation method. The tooth had been restored with a full cast gold crown. The tooth was extremely mobile, had little periodontal support and so was extracted. The patient complained of persistent pain causing by chewing. Radiographic examination following extraction of the tooth revealed underfilling of 3 mm from the apex. We found that the presence of the periapical lesion (radiolucency) was affected by the outcome of root canal therapy. Pain was correlated with a deep periodontal abscess having localized probing defect. The probe did not penetrate into the inflammatory periapical lesion. The presence of X-ray, micro CT and histological changes in the root canal and periapical tissues showed an endodontic failure. A bay-like defect of 3 mm on the apical pulpal wall had been created. The dentin and canal lost through internal resorption were being replaced by osteoid tissue and inflammatory granulation tissue. Dilated blood vessels, macrophages and multinucleated giant cells were prominent in the apical canal. An extensive apical granuloma resulting from canal irritants was seen.

 It was concluded that both periapical and periodontal disease might be present independently, strongly suggesting that pulpectomy and canal obturation should be made flush at the physiological apical foramen.

Abstract : A study was performed to compare the apical closure efficacy of FR-Ca with that of Canals^® in the maxillary four canine teeth of two crab-eating adult monkeys. These teeth had necrotic pulps with periapical radiolucent areas. Each tooth in a monkey had an incompletely formed root with everted canal. External fistulae were seen on the face caused by the two pulpal lesions. Four root canals of these teeth were instrumented and filled during the same session with FR-Ca or Canals^® sealers. In the teeth filled with Canals^®, PTC was placed, and in teeth filled with FR-Ca, FR liquid was dressed.

 In incompletely formed roots, the right canine tooth was filled with lateral condensation of gutta percha cones and Canals^®. The left canine tooth was filled with FR-Ca sealer. In FR-Ca filling, gutta-percha cones were placed about 2 mm short of the apex. In completely formed roots, the left canine tooth was filled by using the former lateral condensation method. In the right canine tooth, FR-Ca sealer was placed to occupy about 1-2 mm of the apical canal space. The cavities were lined with zinc phosphate cement and then sealed with amalgam. The animals were sacrificed 9 months later. After decalcification, serial celloidin sections 15 μm thick were prepared in a buccolingual plane and stained with hematoxylin-eosin.

 Although FR-Ca sealer extruded apically, there were no apparent long-term adverse effects. Apical calcific tissues were observed microscopically. Radiographically, apical healing also progressed with time. In Canals^® to open apex, fibrous cicatrization of periapical tissue was observed and apexification did not occur. In FR-Ca to open apex, periapical closure occurred as a result of what appeared to be inward bending of root sheath, and a calcific bridge was continuous with the cementum of the undisturbed root apex. Loose connective tissue, abundance of fibroblasts, and some macrophage-like cells and multinucleated giant cells were apparent in the periapical periodontium. Inflammation was almost never seen. In a canal of completely formed root with Canals^®, chronic abscess was found with epithelial proliferation, bacterial masses and bacteria invaded dentin chips in the apical lesion. Areas of bone and root resorption were more frequent and apical repairs were not seen in the tooth.