Nondestructive estimation of the strength of dental ceramic materials

Objectives: The aim of this study was to prove a nondestructive method to evaluate the strength of dental ceramic materials with respect to its potentiality and limitations. Methods: The Youngʹs moduli of 13 dental ceramic materials were determined by the resonance frequency method. Additionally, the flexural strengths of eight of these materials were evaluated by the four-point bending test. Strength values for the other five ceramic materials were taken from the literature. The Youngʹs moduli were correlated with the strength values by Hookʹs law, respectively. Results: Youngʹs modulus for ceramics can be determined using a resonance frequency method. Fracture strain values of the ceramic materials tested (with the exception of Empress 2) have fracture strain values between 0.08 and 0.15%. A mean strain can be calculated (0.11%) and used with the value of Youngʹs modulus to estimate fracture strength of ceramics. For the materials evaluated, predicted strength was within 39% of the measured values. Significance: A non-destructive method to estimate strength of dental ceramic materials is possible, even though the accuracy of the predicted values is not very high. Nevertheless, the method permits new materials proposed for dental ceramic restorations to be screened for probable clinical success. Expensive and time-consuming testing would only need to be done on those materials which pass this initial criterion.