Change in elastic modulus of bovine dentine with exposure to a calcium hydroxide paste.

Abstract Objective To determine the effect of calcium hydroxide [Ca(OH) 2 ] paste exposure on the elastic modulus of bovine dentine. Methods Dentine sections (4 mm × 4 mm × 1 mm) were obtained from freshly extracted bovine incisors and placed in dishes containing a 1-mm deep layer of Ca(OH) 2 paste or physiological saline as a control. An ultrasonic device was used to measure the sonic velocities of the longitudinal and shear waves, and the elastic modulus was calculated. Data were examined by analysis of variance followed by the Tukey H.S.D. test in order to compare different storage times. Results Exposure to Ca(OH) 2 paste significantly increased the mean elastic modulus of the dentine from 16.3 to 22.1 GPa. By contrast, the elastic modulus of the control dentine, which was exposed to physiological saline, remained constant. Conclusion These results demonstrate that exposure to Ca(OH) 2 paste increases the elastic modulus of dentine, thereby making it more prone to fracture.