Surface and Nanomechanical Behavior of Human Molars Soaked in Sodium Fluoride

摘要

Nanomechanical properties and microstructures of molar samples soaked in 0.02 wt(percent) sodium fluoride solution were measured using nanoindentation, X-ray diffraction (XRD), and scanning electron microscope (SEM) coupled with energy dispersive spectroscopy (EDS). The results showed that the hardness, stiffness and Young's modulus of the teeth varied after they were soaked in the sodium fluoride solutions. The hardnesses for soaking times of 0, 5, 30, and 60 min were about 3.3, 3.8, 3.2, and 2.6 GPa, respectively. After being soaked in 0.02 wt(percent) sodium fluoride solution for 5 min, the enamel surface formed calcium fluoride or fluoride compounds, enhancing its hardness. As the soaking time increased, the enamel surface released many minerals, which decreased the required deformation energy. When the teeth were soaked for longer than 30 min, the hardness reduced slightly due to the softening of the enamel surface during an erosive process caused by dissolution.