Micro-Endodontic Treatment Of Procedural Accidents M.Bruder*, M.O. Ahlers, U. Platzer (Universitäts-Krankenhaus Eppendorf, Klinik Und Poliklinik Für ZMK-Krankheiten, Abteilung Zahnerhaltung Und Parodontologie, Martinistr. 52, 20246 Hamburg, Germany) The technical equipment for a root-canal-treatment has been extended immensely throughout the last years. Nevertheless, many endodontic cases still fail for a large variety of reasons. Examples of these multiple causes are missed canals, root-perforations, broken instruments or the use of silver points as a root-filling material. In the past and unfortunately in the presence, surgery is chosen too often to resolve such failures although a nonsurgical proceeding frequently provides an improved long-term prognosis. The aim of the present study is to demonstrate with numerous case reports that the operating dental microscope with different levels of magnification and coaxial illumination is the essential instrument which can not be renounced if these failures shall be turned into successes.   Cases:   1. Missed canals can be responsible for a patient`s lasting discomfort after or during a seemingly succesful treatment (Frank, 1974). The recognition of these canals is rendered to the practioner by the enhanced vision and lighting of the working field offered by the microscope.   2. Perforations of the midroot most often occur in curved canals, due to inadequate cleaning and shaping technique or the preparation of a post cavity (Wong, 1997). Depending on their level, size, type and length of time before repair, these perforations can often be treated nonsurgically with the help of the microscope. Following identification of the perforation site, it can be sealed hermetically, provided acces, a certain magnification and a sufficient illumination.   3. Engine-driven rotary instruments sometimes break easily inside the canal (Wong, 1997). To get a three-dimensional impression of the location of the seperated instrument as well as the attempt to loose it with ultrasonic tips is often just possible under a microscope.   4. Silver points do not represent the international standard of care anymore. Still, patients occasionally show up, who were treated that way. These cases should always be retreated (Seltzer et al, 1972; Weine, Rice, 1986). If the point can not be revised in one piece the microscope can support to trace the fractured parts and eliminate them.