Abstract : Background : Aseptic root-canal treatment (aRCT), in which a bacteria-free protocol is used, results in a high success rate of approximately 90%. However, most Japanese patients do not receive aRCT due to unsuitable procedures that put emphasis on saving cost.

 Purpose : The aim of this study was to estimate the cost-effectiveness of aRCT in Japan with a cost-utility analysis (CUA).

 Methods : We used CUA to estimate the cost-effectiveness of aRCT against septic RCT (sRCT) which is thought to be commonly performed in Japan, and evaluated CUA using the incremental cost-effectiveness ratio (ICER). The ICERs were compared with criteria. The expected costs of aRCT were estimated using the fees of Medicaid in the United States and the scheduled fees of the Swedish medical insurance system. The expected cost of sRCT and endodontic surgery (ES) were estimated using the fees of the Japanese reimbursement system. The utility of RCT and ES were quantified with quality-adjusted life years (QALY) calculated by the QOL value of one tooth loss, the rate of RCT failure, and the life expectancy of the median age of the Japanese population.

 Results : In Japan, the ICERs of aRCT compared with sRCT were lower than the smallest criterion, 5,000,000 yen.

 Conclusion : The results of this study revealed that aRCT may be a cost-effective procedure in Japan.

Abstract : Purpose : The purpose of this study was to compare the total preparation times, the pushing and pulling forces and the amount of canal transportation after preparation of resin curved root canal models using the following two kinds of files : RECIPROC^® blue (REB : new material) and RECIPROC^® (RE : conventional file).

 Methods : Resin models that had curved root canals of 30 degrees were used (n=8, each). The total preparation time, and forces required for push load and pull-out load during root canal preparation were measured. Photographs taken before and after preparation of the canal were superimposed. The amounts of canal transportation were measured at 1-mm intervals from the apical foramen to the distance of 8 mm. The data were analyzed by the t-test or Wilcoxon signed-rank test.

 Results : Among all of the total preparation times, the pushing and pulling forces and the amount of canal transportation, no significant difference was observed between the two groups.

 Conclusion : It was suggested that REB is able to prepare a curved canal appropriately as well as RE.

Abstract : Purpose : In order to use NiTi rotary files safely, it is helpful to have a prediction of how many root canals can be cut and how many files will break.

 Materials and Methods : Austenite phase (Endowave, Morita), and R phase (Hyflex CM, Coltene/Whaledent, JIZAI, MANI) NiTi rotary files were examined for fatigue tolerance during root canal enlargement using J-shaped simulated root canals. The fracture cross-section was also observed by SEM.

 Results : When root canal expansion was performed at 300 rpm, 3 Ncm, the number of root canals until the file broke was in the order of JIZAI (53.4±10.7)>Endowave (16.4±4.0)=Hyflex CM (15.8±3.6). When used at 300 rpm, 180° and trigger torque of 0.8 Ncm using OTR of Tri Auto ZX2 (Morita), JIZAI increased the root canal expansion number by about twice, but the others did not make a significant difference. JIZAI was examined at 300 rpm and 500 rpm and OTR because use at 500 rpm is recommended, but there was no difference in service. As a result of observing various fractures by SEM, Hyflex CM and JIZAI showed a more dimpled structure than Endowave. In addition, Hyflex CM and Endowave were more pronounced than JIZAI in the crushing of the blade part.

 Conclusion : JIZAI has greater fatigue resistance than the others, and it was found to rise by nearly twice when used in the OTR of Tri Auto ZX2. The R-phase file was considered to extend and break.