Elastic properties of dentin bonding agents using bulk acoustic waves

Describes the use of bulk acoustic waves to measure elastic and viscous properties of thin dental resin films. Our initial experiments have utilized a 7.3 MHz bulk longitudinal wave resonator fabricated on a Z-cut lithium niobate plate. At first, the frequency dependence of resonator impedance (without resin coating) was measured. This was used to determine effective material constants of the resonator by performing a least-squares fit of measured data with theoretically calculated values. One surface of the resonator was then coated with a thin film of the resin under study. The effect of the coating is to lower the resonant frequency and the quality factor of the resonator. The change in these parameters can be used to calculate the elastic constant C₁₁ and viscosity constant η₁₁ of the resin film. The elastic constant C₄₄ and η₄₄ were similarly determined using a shear wave resonator fabricated on an X-cut lithium niobate plate. Our measurements indicate that mechanical properties of the resin film are a function of the film thickness. Possible reasons for this behavior are discussed. The techniques described here allow one to determine the mechanical properties of dentin resin films. This information is essential in order to understand the clinical behavior of these materials