Differences in Nano-mechanical Properties Between Enamel and Dentin

Objectives: The mechanical properties of hard dental tissues have been the subject of several investigations. The purpose of this study was to measure the different mechanical properties of enamel and dentin using nanoindentation and harmony oscillation technology.
Methods: Freshly extracted human tooth specimens (n=18) were mounted on a nanoindenter. An indentation load rate corresponding to a displacement rate of 10 nm/sec was applied to an indentation depth of 500 nm. Nanoindentation-based elastic modulus (E), plastic hardness (H), static viscoelastic normalized creep (Creep/Pmax), brittleness (E/H) and viscosity (η), and dynamic viscoelastic tangent delta (tan δ) were measured. Tan δ was assessed by continuous stiffness measurements (CSM) that uses the harmonic oscillatory response during the 30-second holding period. Oscillatory force was applied at 45 Hz corresponding to 2 nm of displacement, which is a common operating condition for CSM. The results were statistically analyzed, ANOVA (P<0.001).
Results: The study parameters revealed that except for brittleness, enamel and dentin showed statistically significant differences regarding their inherent mechanical properties.
Conclusions: The complex nature and composition of enamel and dentin is reflected in their behavior and response to mechanical testing. Dentin possesses a resilient property due to its unique ability for dynamic energy dissipation. Enamel tissue that is supported by dentin tends to show less brittleness.