Abstract : In this article, a case of which vertical root fractured tooth was treated with mineral trioxide aggregate is reported. The site of fracture in the fractured tooth extracted intentionally was remodeled outside of the oral cavity and then re-invested after filling with mineral trioxide aggregate. After 3 years, restoration of the surrounding alveolar bone was observed.

Abstract : Mesial roots of mandibular molar teeth were prepared with nickel-titanium GT rotary files as recommended by Buchanan and the traditional step-back method with K-files. Observations were done by computerized tomography to compare, on the horizontal plane, the change in shape and position of a root canal before and after procedures. Following canal shaping, post-operative scans were superimposed on the original images at 1.5, 3.0, 4.5, 6.0, and 7.5 mm from the apex of the roots. Changes in canal area, and changes in shape and positions of canal and thickness of the remaining root structure at strategic levels of the root were analyzed.

 At 1.5 mm from the apex, the crown-down technique with GT files did not show a significant difference between pre- and post-shaping, but the step-back method with K-files showed a buccal canal wall thinner after the procedure than before. The step-back method showed that the mesial canal wall tended to be thinner than the furcal canal wall.

 At 3.0 mm from the apex, with both methods, there was a significant difference, depending on the area, between pre- and post-operation. With the crown-down method the mesio-lingual wall was thinner than the furcal wall. The step-back technique tended to result in thinner extroversion canal walls.

 At 4.5 mm from the apex, both techniques resulted in thinner extroversion canal walls. It was not possible to determine which technique gave thinner results.

 At 6.0 mm from the apex, the crown-down method produced thinner furcal canal walls. Nevertheless, it was not possible to evaluate which of the furcal canal wall or the mesial (extroversion) canal was thinner.

 At 7.5 mm from the apex, both techniques resulted in thinner furcal canal walls than the extroversion walls. The crown-down method showed more efficient filling effect on root canal structure than the step-back method.

 The GT rotary file produced good canal shapes in root canals compared to the conventional K-file method.

Abstract : Many rotary nickel titanium file systems have been developed for root canal enlargement. Curved and calcified root canals are not easily enlarged by a stainless-steel file, so EDTA and other chelating agents are commonly used to help instruments penetrate and enlarge constricted canals. Many dentists often experience clinical cases where penetration is hard to achieve and/or enlargement takes considerable time. The aim of this study was to assess the usefulness of FlexMaster Ni-Ti rotary files in preparing curved root canals. Basic and versatile applications on extracted human teeth as well as clinical cases are introduced.

Abstract : Nickel-titanium rotary endodontic instruments have clinical advantages in endodontic treatment especially for curved root canals. In daily clinical settings, Ni-Ti instruments are heat-sterilized by autoclave and sometimes chemically disinfected by soaking in NaClO solution. The aim of this study was to evaluate the influence of autoclave heat sterilization and NaClO chemical disinfection on the mechanical properties of Ni-Ti rotary instruments using a bending test and differential scanning calorimetry (DSC). Three types of Ni-Ti rotary instruments, ProFile^®.06tapers, ProFile^® Series 29, and ProFile^® Orifice Shaper, as well as a and stainless-steel hand K-file, were used in this study. From the results of the bending test, there was no significant difference in bending load among all groups. The bending load of nickel-titanium alloy did not change by autoclave heat sterilization at 121°C or by 6% NaClO chemical disinfection. From the results of DSC, the austenitic transformation finishing temperature (A_f) point after each sterilizing procedure did not change and remained lower than 37°C, which was suitable to exhibit super-elasticity. The mechanical properties of the nickel-titanium rotary endodontic instruments were not significantly affected by autoclave heat sterilization (121°C, 2 atm) or by 6% NaClO chemical disinfection for 30 minutes. Therefore, the sterilizing procedures for nickel-titanium instruments, including autoclave heat sterilization and NaClO chemical disinfection, may be less influential compared to their history of use when discarding the instruments.

Abstract : The aim of this study was to evaluate the effect of root canal morphology on sealer cement thickness using different root canal obturation techniques. Fifteen extracted human central incisors with a round canal and fifteen upper single-rooted premolars with an oval canal were used. After root canal preparation, the incisors and premolars were randomly divided into three groups, respectively, and obturated with one of three techniques : lateral condensation method (LC group), vertical condensation method with System B and ObturaⅡ (VC group), or injection method with ObturaⅡ (IN group). The thickness of sealer cement at the cross sectional plane 1 mm from the apex was measured under ×100 magnification. There were no significant differences among the obturation techniques except for incisors of the IN group, while root canal morphology significantly affected sealer thickness in the VC group (p<0.05). It was concluded that sealer cement thickness was not affected by the lateral condensation method or vertical condensation method with System B and ObturaⅡ.