Determination of ultrasonic velocity in human enamel and dentine

Acoustic velocity data have been obtained preparatory to investigation of high frequency ultrasound as a non-invasive imaging technique for dental hard tissues and their pathology. In vitro studies were conducted on extracted human permanent teeth. Pulse-echo ultrasound of 18 MHz centre frequency and approx. 150 ns pulse duration successfully detected the front and back surfaces of 0.45-1.07 mm thick sections of enamel and of dentine. Water was used as the coupling agent. The oscilloscope traces of the echoes from pure enamel and pure dentine were similar. The longitudinal ultrasonic velocities for pure enamel and dentine were experimentally determined for a number of teeth in different planes of section. For enamel in longitudinal and transverse sections, the mean ultrasonic velocities were 6150 +/- 140 and 6500 +/- 190 m/s respectively. For dentine in longitudinal section, the mean ultrasonic velocity was 4050 +/- 30 m/s.