Theoretical imaging study of early caries by a laser induced Rayleigh wave.

Vivo human teeth are scanned by computed tomography through three-dimensional (3D) reconstruction technology. Geometric models of teeth are built. Based on that, a physical model of the laser induced acoustic waves propagating in teeth is established, and the finite element method is used to solve this physical model. As the velocity of the Rayleigh wave is sensitive to the elastic modulus of the teeth, the parameters, such as the position, demineralization degree, depth, and morphology of the caries, can be evaluated by the velocity field of the Rayleigh wave, which propagate in teeth. Furthermore, by the frequency domain characters of surface acoustic waves, the depth of the caries region can be evaluated. Therefore, the 3D evaluation method is established to develop the nondestructive and quantitative detection of the early stages of caries.