An apparatus for removing organic material from a root canal of a tooth includes a liquid jet assembly, a sensor and a controller. The liquid jet assembly is configured to produce a high velocity beam of liquid capable of cleaning the root canal of organic material. The sensor is configured to detect completion of the cleaning and to produce a signal in response. The controller is configured to communicate a shut-off signal to the liquid jet assembly upon receipt of the signal from the sensor based on an acoustic signature. The acoustic signature comprises cavitation induced effects how an amplitude of the signal changes during cleaning, a high frequency acoustic signal or a low frequency acoustic signal.
