Figure 3. The Young’s modulus as reported in the literature over the past 50 years. The data prior to 1999 appear in tabular form in the reference by Kinney et al. (1999). Data after 1999 are from Huo et al. (2000), Kinney et al. (2001a), Kishen et al. (2000), and Palamara et al. (2000). In the past few years, there has been a four-fold variation in the reported magnitude of the Young’s modulus; the uncertainty in its value appears to be expanding with time. The uncertainty in the magnitude of the Young’s modulus is probably not reflective of the actual variations in the mechanical properties of dentin. Rather, the uncertainty most likely arises from either a viscoelastic response (stress relaxation) or experimental artifact.