Dental detection apparatus for position of root apex

A dental detection apparatus for locating the position of a root apex of a tooth in a body of a dental patient comprising:

• a reamer for insertion into a root canal of said tooth;
• a single electrode contacting said body of said dental patient near said tooth;
• two oscillators which generate currents having two different frequencies;
• said oscillators connected to said reamer;
• said currents passing through said reamer and said body as attenuated currents to said single electrode;
• a differential amplifier connected to said single electrode for detecting a difference .sub.D V of respective impedance variations in said attenuated currents;
• a direct current amplifier connected to said differential amplifier for amplifying the output of said differential amplifier;
• a meter connected to said direct current amplifier for displaying the output of said direct current amplifier;
• a comparator connected to an output side of said direct current amplifier and to an input side of a two contact analog switch,
• a binary up/down counter connected to an output side of said two contact analog switch for switching said counter to an up or to a down condition depending on an input frequency of said two contact analog switch;
• a direct current/alternating current converter connected to an output side of said binary up/down counter;
• an output side of said direct current/alternating current converter connected to said differential amplifier to create an offset of said differential amplifier;
• an automatic calibration switch connected to one of said two oscillators for passing a frequency signal from said one of said two oscillators when switched on to said binary up/down counter through said two contact analog switch;
• wherein switching on said automatic calibration switch when said reamer is first inserted into said root canal determines a condition of said root canal displayed on said meter and when thereafter switching off said automatic calibration switch enables further insertion of said reamer to compensate for said condition and locate said root apex by display on said meter.