Abstract : By introducing the anaerobic culture system, it becomes possible to evaluate the results of endodontic treatment effectively. In the past two years, we have applied the high-frequency endodontic apparatus, CM-009C, on 600 cases in our clinic during the endodontic treatment, resulting in a significant shortening of treatment period. The test results are described in this report.

 Materials and Methods :

 Blood-agar culture medium based on thje CDC receipt, CM-009C, was used in the study. Anaerobic culture was conducted in each case of our patients during the period from November 1996 to November 1998. Numbber of cases totaled 600.

 The count of times needed to achieve a bacteria-free state was investigated. Also, in some cases, CM-009C was applied in the midway for comparison.

 Results :

 On average, the mean of endodontic treatment times to achieve a bacteria-free state is 5 times. The bacteria-free state is evaluated by anaerobic culture. It was found that the mean count of treatment times was 6.5 (395 cases) before introduction of the high-frequency endodontic treatment. And the mean count of treatment times was 3 (99 cases) after introduction of the high-frequency endodontic treatment.

 Conclusion :

 It is found that higgh-frequency treatment is able to decrease effectively the times of endodontic treatment.

Abstract : In endodontic surgery resection of the apical 3 to 4 mm of the root is designed to eliminate the majority of accessory and lateral canals. Although it is known that uncleaned and unfilled accessory and lateral canals in the apical region are a primary cause of endodontic failures, to date there are few reports on the frequency of accessory canals on the resected root surface. The purpose of this study was to establish the frequency of such canals in the apical 4 mm of the root and to evaluate the effectiveness of methylene blue stain for their detection. One hundred extracted human maxillary incisors were instrumented and obturated and each root was resected perpendicular to its long axis in 1-mm increments. The resected surfaces were stained with 1% methylene blue and examined at 26X magnification. In 64 percent of the maxillary incisor teeth, accessory canals were observed on the resected surfaces. Beginning at the apex, their incidence decreased with successive 1 mm resections. The number of accessory canals at the 1 mm and 2 mm levels was significantly greater than at the 3 mm and 4 mm levels (p<0.05, chi-square test). This suggests that at least 3 mm of the apex should be resected to eliminate the accessory canals. The incidence of accessory canals observed by using methylene blue staining was almost the same as that in previous reports on root canal morphology. This indicates that methylene blue is an effective medium for detecting accessory canals on the resected root surface under a microscope during apical surgery.

Abstract : We have been reported that the generated hydroxyl radical from mixed solution of Cu²⁺ and H₂O₂ and Cu²⁺ solution had bactericidal effect ; also when smear layer on the root canal wall was irrigated with Cu²⁺/H₂O₂ mixed solution, the shape of the smear layer changed into hyaloid structure.

 In this study, we examined the effect of on the shape of the smear layer accumulated on the root canal wall the by SEM.

 In conclusion, The shape of the smear layer on the root canal dentin was not changed with 1 mM CuCl₂ solution. The hyaloid structure was not observed both in immersion and irrigation by CuCl₂ solution.

Abstract : We encountered an opportunity to employ System B, that developed by Buchanan LS in order to solve a defect the operation and working time of Schilder method.

 The purpose of this study was compare the sealing ability of the conventional method ( : lateral condensation technique), main gutta-percha point and Obturation gutta by NT condenser ( : Hybrid technique) and new obturation technique by System B ( : continuous wave of condensation technique).

 The root canals of sixty-four extracted mandibular incisors were endodontically prepared and obturated by the three techniques and immersed in the India ink. The penetration distance of the dye was measured from apex of the root. And then, observed obturated gutta-percha to root canal wall by scanning electron microscope (SEM).

 The results were as follows :

 1. The penetration distance of dye on obturated root canals were observed with order of lateral condensation technique, obturated with System B technique, hybrid technique. However, at a penetration distance, there were not difference among result of Dunn multiple comparison test, each.

 2. At hybrid technique, it was 65.0% that was not penetration of dye from apex of the root. System B technique was 55.0%, lateral condensation technique was 45.0%.

 3. Hybrid technique and System B technique were guessed to be capability for apical seal by two-way analysis (test for the proportion).

 4. By Fisher’s exact probability test, it was guessed that the method of hybrid have most sealing ability.

 5. In three obturation technique, it was very good adaptation with entire canal wall and gutta-percha with SEM. But, when do Down packing with System B, we observed a large space inside root canal, it were suggested, as must do Back packing inevitably.

 Finally, the obturation technique with System B, it became clear to be an equality or somewhat good method with conventional methods. However, when doing Down packing, there was a possibility to space, or vertical crack.

Abstract : We could successfully and effectively remove separated files using the micro-File System (Dentsply Maillefer, Switzerland) and ultrasonic instruments under a microscope.

 The separated files were exposed by removing surrounding dentin with a ST21 ultrasonic tip (Osada, Tokyo), and a micro-Opener was inserted between the separated file and dentinal wall. Then, the micro-Opener was pushed back and forth to loosen the wedged file. When the separated instrument was not loosened, the ST21 ultrasonic tip was applied to bypass it for creating extra space. Then, it was grasped and dragged out of the canal with a micro-Debrider.

 Our technical advantage is the use of high magnification and illumination of the microscope, resulting in an easy manipulation of the micro-File System and an ultrasonic tip, which may also make it possible to retreat other complicated cases.