INSTRUMENT OF PROBING THE LENGTH OF A ROOT CANAL OF THE TOOTH

摘要

An instrument for measuring the length of a root canal of the tooth provided with a transistor amplifier, at the input side thereof a probe needle for inserting into the root canal and at the output side thereof an oral mucous membrane conductor. Between the point of the probe needle and the oral mucous membrane conductor is electrically connected through a human body to form a circuit whereby the variations in low frequency oscillation due to feedback are delivered as oscillation sounds to the ear of the dentist. When the predetermined degree of oscillation sound comes to be audible, the length of the root canal is measured with an impregnated length of the probe.