A Root Canal File Working Depth Measuring Instrument Based on Impedance Method

To address the issue of accurately and real-time displaying the position of the root canal file tip during root canal preparation surgery, a real-time measurement system based on the capacitive characteristics of the root canal is proposed. The system calculates the position of the root canal file tip within the root canal by measuring the capacitive reactance of the equivalent capacitor formed by the root canal and the root canal file. The system utilizes a DDS signal source centered on the AD9833 to generate an AC signal, and an amplification module centered on the AD8221 converts the difficult-to-measure root canal current signal into a voltage signal suitable for calculation. The PCF8591 chip is used to acquire the voltage signal during the measurement of root canal capacitive reactance in real time, and the signal value is transmitted to the STM32 microcontroller. After processing the acquired signal, the microcontroller obtains the impedance value of the root canal capacitance at different frequencies, thereby calculating the position of the root canal file tip. Experiments show that the system provides accurate and highly sensitive test results for the apex position, with a suitable manufacturing cost, effectively improving the efficiency of root canal surgery.