Abstract An ultrasonic pulse-echo system has been successfully employed to detect the dentino-enamel junction and the dentino-pulp interface. It has proved possible to measure the velocity of sound for longitudinal waves in intact teeth. Human incisors, bovine incisors and dog molars have been studied with the equipment. From the time intervals between echoes and by measuring the thickness of each layer, the sonic velocity in the enamel and dentine in each kind of tooth was determined. The major objective was to evaluate the performance of a pulse-echo system designed specifically for use with hard dental tissues with the ultimate aim of providing ultrasonic dental diagnosis. A thin disc-shaped piezoelectric element was employed as the sensitive part of the transducer, serving as both the sound source and sound receiver. Pulse shapes in the form of a “W”, 150 × 10 −9 sec duration, were generated by an electronic trigger. Sound was conducted to the tooth through the tip of a small diameter aluminium rod rather than through a liquid medium like water or mercury. The echo returned along the same path to the piezoelectric disc where it was converted into an electrical signal and viewed or photographed on an oscilloscope. In order to ensure sonic coupling, a small flat spot 3 mm dia. was ground on the tooth. In certain instances it was possible to obtain an echogram without this tooth preparation. Nominal depth resolution was estimated to be at least 0.5 mm in dental enamel, but it was possible to resolve enamel layers less than 0.3 mm. Pulse echoes from the dentino-enamel junction and the pulp chamber wall were readily detected in all teeth. Sonic velocity in human enamel was found to be 6250 m/sec, in human dentine 3800 m/sec and somewhat lower in bovine and dog teeth. An experiment on an anaesthetized dog was performed to determine if the sonic velocity in vital teeth is different from extracted teeth. No change in the echogram was detected from that of vital teeth for as much as 24 hr after extraction.
[1]
G BAUM,et al.
Observation of Internal Structures of Teeth by Ultrasonography
,
1963,
Science.
[2]
G. Paffenbarger,et al.
Compressive properties of hard tooth tissues and some restorative materials.
,
1960,
Journal of the American Dental Association.
[3]
G Kossoff,et al.
Examination of the contents of the pulp cavity in teeth.
,
1966,
Ultrasonics.
[4]
S. Lees.
Specific acoustic impedance of enamel and dentine.
,
1968,
Archives of oral biology.
[5]
D. Berlincourt,et al.
Piezoelectric transducer materials
,
1965
.