Root canal preparation was performed with the new Canal-Finder-System in extracted teeth and in simulated root canals in resin blocks. The results of SEM- and stereomicroscopic investigation showed severe alterations of root canal morphology in the apical part of the canal in many cases. Excellently cleaned and shaped canal walls were found as well as parts, which were not instrumented at all or covered with smear layer and debris. The Canal-Finder-System was found to be a good and suitable device for the initial instrumentation of narrow and severely curved canals, but cannot replace hand instrumentation as the standard method of root canal preparation.