Investigations of Sound and Carious Dentin Using Ultrasound Velocity and Scanning Electron Microscopy-An In-vitro Study

Abstract

Aim: To investigate structural changes in human dentin due to aging process or caries using ultrasound velocity and scanning electron microscopy (SEM). An in-vitro study conducted on human dentin samples. Dentin samples were prepared from the extracted molars using a computerized water-cooled cutting machine. Each sample was 7mm long, 5mm wide and 2mm thick [± 0.1mm]. Fifteen dentin samples were prepared for the three experimental groups. Each group consists of five dentin samples. Group 1 (20year old sound dentin), group 2 (50year old sound dentin) and group 3 (carious dentin). Ultrasound velocity measurements were carried-out on dentin samples and the data were compiled and analyzed using Wave Star software and Minitab 12.1 software. After the ultrasonic measurements, the dentin samples were characterized using SEM. Results: Ultrasonic measurements showed that the arrival time of wave signal was 35.1µs in 50year old dentin, 35.8µs in 20year old dentin and 36.4µs in carious dentin, and there were significant differences (p < 0.05 at 95% confidence level) in the mean values of the ultrasonic velocity measurements between group 1 and group 2, and between group 2 and group 3. Based on the SEM micrographs, the structural changes can be seen clearly in 50year old dentin due to the aging process and in carious dentin due to caries. Conclusion: Results indicated that structural changes of human dentin due to aging process and caries can be distinguished using ultrasonic velocity, however, further work is required on larger sample size, intermediate ages and restored teeth.