2008 Volume 51 Issue 2 Pages 123-129
An equation has been proposed describing the relation between √KHN and mineral content for demineralized enamel (vol%=4.3(√KHN)+11.3). However, it is unknown whether mineral content profiles of remineralized enamel are equivalent to hardness profiles. Our objective was to compare profiles of transversal microradiography and hardness for remineralized enamel cross sections using a nano-indentation technique. Bovine enamel subsurface lesions were created in a lactic acid gel system at pH4.6 for a ten-day period. After the period, lesions were remineralized for two weeks at 37℃. Before and after the remineralization, 150μm specimens were cut from the enamel blocks and transversal microradiographs were taken. Simultaneously, nano-indentation testing was performed on cross sections of the lesions into the underlying sound enamel, starting from 10μm in from the anatomical surface at 10μm intervals. Microradiography of the thin specimens and nano-hardness values at the cross section resulted in similar subsurface lesion profiles after demineralization. Although mineral volume percent of the remineralized surface and lesion body gave recoveries up to 68-87%, recovery rates of nano-hardness value were limited to 30-50%. Further, while the recovery rate of 30μm depth nano-hardness value was 30.5%, the recovery rate of conversion from mineral volume% using the formula was 39.1%. Though the mineral volume percent of remineralization recovered remarkably, the nano-hardness values did not recover to the same degree as the volume percentage mineral. From an ultrastructural point, the remineralization process seems to be more complex than the demineralization process. Therefore, remineralization strategies to recover the mineral should be developed with concomitant recovery of lesion consolidation.
