[Relationship between the microstructure and nanohardness of dentin and enamel of human teeth].

Objective: To investigate the relationship between the nanohardness and microstructure of the dentin and enamel of human teeth.

Methods: Nano indentation was used to determine the nanohardness of enamel and dentin; TEM and IR were utilized to observe the microstructure and crystalline characteristic.

Results: The mean nanohardness of the enamel [(4.92 +/- 0.40) GPa] was significantly higher than that of dentin [(1.17 +/- 0.14) GPa]. A large quantity of hydroxyapatite (HA) crystals and uniform lattice stripe were found in enamel but not in dentin.

Conclusions: The difference of nanohardness between enamel and dentin is related to their density, the inorganic morphology and phase structure.