The laterally varying ultrasonic velocity in the dentin of human teeth

There is no quantitative description available that numerically relates any acoustic parameter pattern or the local elastic behaviour to any standardized geometrical positions within human teeth. However, the speed of ultrasound at 20 MHz varies in different parts of teeth. Great differences occur between the values attributed to longitudinal waves that propagate in the three mineralized human hard tissues at identical relative tooth width portions [John, C., 2004. The corono-apically varying ultrasonic velocity in human hard dental tissues. Journal of the Acoustical Society of America 116, 545-556]. The aim of this work was to investigate the distribution of the longitudinal ultrasound velocity (LUV) at distinct relative tooth width portions and at a height level of 8 mm relative to the coronal reference. Individual tooth widths w were accounted for, and a standardized, dimensionless radial distances variable X=|x/w-0.5| was utilized to express the radial position of measurements in a unified way. The observed lateral increase in LUV of 21 specimens along X was approximated. A Padé shape function predicts the lower contour of the envelope curve of all the individual LUV distributions. Individual residuals and coefficients are provided for LUV=a+b·ln(X)·X·X, where a and b represent individual intercepts and slope factors (e.g. a=3206m/s and b=-4184m/s), respectively.