New principle and method for measuring the root canal length.

A new method for locating the apical constriction and foramen in vivo has been developed and tested on an in vitro model prepared with an extracted human tooth. The results indicate the feasibility of this method for clinical use. Comment: The device described permits length determination in an electrolyte-filled canal. The problem with such devices seems to be that prior to instrumentation (when length determination is usually desired), the exact degree and nature of canal hydration are unpredictable. After instrumentation, canals likely have to be open to at least a #35 instrument before a solution of any kind can be predictably delivered throughout the canal. This may be too large a size to take the apical several millimeters of a fine or tortuous canal. Nevertheless, the device seems an advance over previous electrical gadgets.