Abstract : This study evaluated the mechanical properties of a newly developed soft-type gutta-percha point, FGP-3 (GC Co., Ltd.), which is designed to have much elasticity at room temperature and flexibility at around body temperature.

 To determine the mechanical properties of FGP-3 in comparison with those of two other commercially available gutta-percha points, we conducted tensile tests at room temperature and at 37°C. Stress-strain curves generated from the data were plotted to calculate the elastic modulus, yield strength, percentage elongation at yield point, resilience and total energy (toughness).

 The results of the tests revealed that FGP-3 had the largest values for yield strength, resilience, and toughness at room temperature and at 37°C, whereas FGP-3 had the smallest values for the elastic coefficient at either temperature. FGP-3 had higher plasticity at 37°C than at room temperature.

 Our results suggest that this newly developed soft-type gutta-percha point, FGP-3, has excellent physical characteristics of elasticity, flexibility, and plasticity, thus making it clinically suitable as a master point for use in the lateral condensation method.

Abstract : This study evaluated the physical properties, sealing ability and tissue irritant of newly-developed paste-paste sealers (Normal type, Quick type), and compared them with a zinc oxide-eugenol sealer, Canals, as a control.

 The findings were as follows :

 1. With the paste-paste type, the appropriate quantity for use could be easily controlled, and mixing procedure was easier and faster than for Canals.

 2. The physical properties of the Normal type and Quick type showed values within the limits of the ISO standard.

 3. Two types with different operation time were formulated to allow for different situations of root canal filling operation.

 4. No significant differences were found among the tested materials in an apical dye leakage study by the methods of lateral condensation and heating gutta-percha. Both the Normal and Quick types showed the same degree of leakage as Canals, and apical sealing ability was suggested to be equal for clinical use.

 5. The histopathological view showed a very slight inflammatory change at periapical tissue compared with a pulp chamber organization. The Normal type, Quick type and Canals showed similar extent of inflammatory change and are expected to be safe for clinical use.

Abstract : Pulp necrosis is a relatively rare, but serious complication that may occur following autotransplantation of teeth with incompletely formed roots. This report describes five cases where apexification or apexogenesis was successful for autotransplanted developing teeth that had undergone pulp necrosis with or without external inflammatory root resorption. Endodontic treatment included debridement of the root canal system followed by interim root canal filling with calcium hydroxide, which was replaced at 2-week to 3-month intervals. In one case of partial pulp necrosis, pulpotomy was carried out at the apical one-third level. Deposition of hard tissues in the apical region was monitored with radiographs, tactile sensation and a surgical operating microscope. All cases were obturated with thermoplasticized gutta-percha after 3 to 16 months of interim calcium hydroxide filling. At the time of obturation, hard tissue deposition at the apical region and/or reduction in the size of periapical radiolucency were evident, whereas no signs of active external resorption were seen. These results suggest that long-term treatment with calcium hydroxide is an effective treatment modality for autotransplanted developing teeth with pulp necrosis.

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.