Abstract : The aim of this study was to visualize the fluid dynamics during Er:YAG laser-activated irrigation, using buoyant tracer particles in combination with a high-speed camera. After high-speed imaging together with particle image velocimetry (PIV) of the flow in a distilled-water-filled transparent model with two canals, an analysis was conducted using fluid-analysis software. Both cone-shaped and flat-end tips placed in the space corresponding to the coronal portion of the pulp chamber as well as 1 mm deep in the canal generated a similar fluid flow, in the apical half area of the canal. An increased output power tended to show a higher agitation effect of irrigant. Furthermore, the tip position in the upper chamber revealed a wider fluid flow compared with that in the intra-canal. In conclusion, Er:YAG laser, even at a low power setting, might produce efficient streaming in the canal and be a promising irrigation method.

Abstract : We examined cases in which bacterial reduction by common retreatment methods was unsuccessful. In the 300 cases studied, bacterial reduction was not achieved in 12 teeth (4%), all of which showed persistent presence of root canal bacteria. The 12 cases were divided into three types : affected teeth with apical patency of #60 k-file or larger, affected teeth that showed apical radiolucency with a size of the little finger or larger, and patients with significantly impaired so-called host resistance including those who were receiving anticancer drugs or taking steroids for incurable diseases.

Abstract : Horizontal root fracture occurs more commonly in anterior teeth of young people due to trauma, however, it is very rare in the molar region. In addition, due to the difficulty of treating horizontal fractured molars, most cases undergo tooth extraction. In this case report, a distobuccal root on the maxillary left second molar of a 41-year female patient was separated horizontally at the furcation level. The separated root was taken and the tooth could be saved.