Experimental evaluation of human teeth using noninvasive ultrasound: echodentography.

Anomalies present in the hard tissue of teeth are manifested in several ways such as cavities, decay, and caries. The most extensively and commonly used diagnostic modality for the assessment of these abnormalities are x-rays. Unfortunately, these rays are harmful to the human body and may be a source of health risk. This work describes the development of a new testing technique that uses ultrasound designed to complement, or even replace, existing tools used in dentistry applications. Previous studies have shown several models of acoustic field simulation, propagation, and interaction of ultrasound with the layers of several tooth structures. In this paper, experimental data is gathered for the purpose of assessing the viability of this technique in an attempt to detect cavities and fractures in extracted human teeth. A low-intensity, high-frequency ultrasonic set-up is used in all in vitro tests. Four cases have been examined: an intact tooth, a tooth containing an amalgam restoration and a natural surface fissure, a tooth containing a machine side-drilled hole that mimics a cavity, and a calcified tooth--a rare naturally occurring condition. Upon analysis of the obtained A-scans and B-scans, it is verified that these experimental measurements confirm predictions reported in earlier finite element and transmission line studies and suggest that ultrasound is a valuable tool which has the potential to be an addition to, or even an improvement upon, current dental imaging systems.