Abstract : This study examined factors in the generation of voids in gutta-percha by the warmed gutta-percha method. Eighty extracted human teeth with single straight root were used. After root canal preparation, the teeth were divided into 8 groups of 10 teeth each based on 3 factors : master apical file size (＃35 or ＃60), position of an ObturaⅡ needle tip from the apex (3 or 6 mm) and repetition times of back packing (once or three times). Dental radiographs of root-filled teeth were taken to measure the area of Type 1 voids that were observed between down pack and back pack. The number of Type 2 voids observed inside the back packed gutta-percha was counted on radiographs. The area of Type 1 voids and the number of Type 2 voids on the radiographs were significantly larger when the tip of the ObturaⅡ needle was positioned 6 mm rather than 3 mm from the apex (p<0.05). We concluded that voids in gutta-percha generated by the warmed gutta-percha method could be minimized by inserting a needle tip for back pack to the upper surface of the down-packed mass of gutta-percha.

Abstract : This study was designed to understand the effects of root-end filling materials on the osteoblast-like differentiation of human periodontal ligament cells (HPLF). The cells were cultured with two dental materials, Mineral Trioxide Aggregate (MTA) and Super-Bond (SB) in the presence of the medium including 2 mM β-glycerophosphate and 50 μg/mL ascorbic acid (DM, differentiation medium), or the medium without these reagents (CM, control medium). The culture of HPLF alone (Cont) in DM or CM was done as a control. These cultured cells were examined for mineralization activity, alkaline phosphatase (ALPase) activity, and the expressions of Runx2, Osteopontin (OPN), and Osteocalcin (OCN) mRNA. In four weeks of culture, the sequence of the formation of mineralized matrix was MTA (DM)>MTA (CM)≧SB (DM)>Cont (DM)>SB (CM)=Cont (CM). In two weeks, ALPase activity was stimulated in all DM-cultured groups, but not so much in CM-cultured groups. The expressions of Runx2, OPN, and OCN mRNA were up-regulated in not only all DM-treated groups, but also a MTA (CM) group. These results suggest that DM stimulates the HPLF differentiation, albeit with MTA or SB, and further that MTA alone could up-regulate OPN and OCN expressions in HPLF to induce their differentiation.

Abstract : In the present study, the biocompatibility of mineral trioxide aggregate (MTA) to the revascularization of the connective tissues was evaluated by using the improved rabbit ear chamber, in vivo. Thirty improved rabbit ear chambers were prepared in 16 male albino-strain rabbits. Ten chambers were provided for MTA, and the remaining 20 chambers were used for a calcium hydroxide-containing root canal sealer (Sealapex) and Canals respectively. A volume of approximately 1.5 mm³ of each material was inserted into the chamber and the interaction between the vascular tissue and materials was observed by biomicroscopy at 1 week and 4 weeks. The results revealed that revascularization of connective tissue took place with complete recovery of microcirculation within 4 weeks in MTA, Sealapex and Canals. However, the precipitate-barrier and brown zone around the periphery of Sealapex and the gray zone around the periphery of Canals were not observed in MTA-inserted chambers and the newly-formed blood vessels covered on MTA. It can be concluded that MTA is biocompatible and does not produce any adverse site effect on microcirculation of the connective tissue.

Abstract : 3DX Multi Image Micro CT^® is a newly developed limited cone beam X-ray CT for practical use.

 3DX images were taken for two cases of teeth with vertically fractured roots and compared with dental radiographs. One case showed a narrow radiolucent area around the palatal root on 3DX images, which had been difficult to detect on the dental radiograph. The other case showed an actual separation of the root on 3DX images.

 This new device offers three-dimensional images of teeth and more detailed information than dental radiographs. 3DX may be useful to examine cases of root fracture.