Exposimetry of low-frequency ultrasonic dental devices

In low-frequency (20-40-kHz) ultrasonic devices used in dentistry the ultrasound is conducted to the tooth either via a metal waveguide oscillating predominantly in its longitudinal mode or via metal files or reamers driven to vibrate transversely or longitudinally at the same frequency as the transducer. All of these arrangements have unique coupling problems, so that it is difficult to estimate how much ultrasonic energy enters the tooth and therefore what its biological effects might be. As a first step, it is proposed that the maximum displacement amplitudes of that part of the instrument that contacts the tooth be measured to obtain some estimate of the ;acoustic output' of each instrument. These measurements are necessary because of the wide variations in the efficiency of the transduction process between different probe designs (i.e., the interchangeable inserts) powered by the same handpiece, or by the same insert powered by different but compatible generators from the same manufacturer. It is suggested that this information will also improve the ability of clinical users of these devices to reproduce each other's techniques and procedures, and thus make it possible to reduce the number of contradictory claims regarding their clinical efficiency.