Ultrasonic and Microscopic Evaluation of Human Dentine

The bulk of human tooth made of dentine layer. Defects of dentine structure can occur due to caries disease or age. One of the age-related changes in dentine structure is formation of peritubular dentine on the inner walls of dentinal tubules leading to complete closure of tubules. Ultrasound is safe, fast and non-invasive technique. In the last decade, the popularity of the technique has increased in dental research. Several studies have shown that the technique can detect different layers of tooth and tooth defects due to caries. No published studies have been made for the effect of age on ultrasonic measurements of human dentine. Such studies would provide baseline information for ultrasonic measurements.

Objectives: the aim of the present was to investigate the effect of structural changes due to age and caries on the ultrasonic properties of human dentine by using ultrasound and environmental scanning electron microscopy (ESEM).

Methods: Dentine samples were prepared from extracted sound third molars of known patient age. Ultrasonic measurements were carried out on dentine samples using time-of-flight technique to measure velocity of sound.

A number of validation experiments were performed prior to conducting ultrasonic investigations on dentine samples. These consisted of measuring the ultrasonic cell without sample and carious dentine samples. After performing all ultrasonic measurements, dentine samples were examined under ESEM to correlate the ultrasonic measurements with their structure.

Results: The results of ultrasound measurements of dentine samples clearly demonstrate that sound velocity changes with age.

ESEM investigation of dentine samples showed that the number of dentinal tubules and their diameter has been found to decrease with increasing age.

Conclusion: In spite of increasing use of ultrasound technique to understand ultrasonic properties of teeth, it is clear from this study that local structural variations have a marked influence.