An in vitro test of a simplified model to demonstrate the operation of electronic root canal measuring devices.

This article describes an in vitro test of the accuracy of a model for demonstrating the operation of electronic canal length measuring devices (ECLMDs). The model is made from commercially available gelatin which is mixed with sterile saline solution. Extracted human canine and anterior teeth with fully formed apices had access preparations and complete pulpectomies before drying the canals with paper points. The tooth length was determined with an Exact-A-Pex using the gelatin test model. When the apex locator green light-emitting diode indicated 1.5 mm from the apex, the file length to the nearest 0.5 mm was measured with a rubber stop. This length was compared with the length determined by visualization of the tip of a #10 K-Flex file at the foramen. This method was repeated with the Foramatron IV using the instrument's digital reading of zero as the apex location and root canal length. There was complete agreement as to canal length between electronic root canal measuring devices and visual observations. This indicates that the gelatin test model is an accurate in vitro method of determining canal length.