Patent ID: 7326053

Claim:
An apparatus for determining the apex of a dental root canal in a tooth of a patient, said apparatus comprising a dental instrument having an electrically conductive shaft with a leading edge adapted for insertion in the root canal, said apparatus further comprising, in combination: a gain control circuit; a software operated microcontroller having a memory, an analog-to-digital converter (ADC) and a square wave pulse generator; said pulse generator producing a pulse signal having square wave pulses with a first period (T 1 ) separated by an inactive, second period (T 2 ) which is longer than said first period (T 2 >T 1 ), and supplying said pulse signal to said gain control circuit which controls the amplitude of said pulses; a driver receiving said pulse signal from said gain control circuit and supplying said pulse signal to said electrically conductive shaft, said dental instrument having an electrode connectable with tissue of the patient; an input buffer receiving signals from said electrode of said dental instrument and supplying said signals to said ADC; the software of said microcontroller performing measurements of the power of said pulse signal and calculating a medial estimate of power; and a display, coupled to said microcontroller, for exhibiting said medial estimate of power and displaying data concerning the distance of the leading edge of said electrically conductive shaft from the apex of the root canal.