| Budget Amount *help |
¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 2000: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1999: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
1). Knoop hardness to the primary dentin
Knoop hardness number (KNH) were measured on the caries decayed dentin of primary anterior teeth and statistical analysis was done. As the results, the KHN were significantly decreased from the outer layer to inner layer of dentin on the sound side. The KHN of the under caries region and the KHN of the innermost region both on the carious and sound side were significantly lower than those of outer regions. The KNH of the under cavity area showed significantly lower than those of the regions, that were equivqlent to the under cavity areas, on the sound side. The KHN of the adjacent noncavity areas on the carious side also showed significantly lower tendency than those of the regions, that were equivqlent to the adjacent noncavity areas, on the sound side. Traansparent dentin was softer than sound dentin.
2). Correlations between Knoop hardness and Ca, P, Ca/Pand Mg
Specimens that were embedded in black compound and coated by carbon were point-analyz
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ed using EDX.In almost all measured areas, no significant correlation was observed between KHN and Ca, P, Ca/P and Mg.
3). Effects of caries removal methods on hardness to underdecay primary dentin
The primary canine that were caries extended into dentin were sectioned. For one side of the sectioned specimens, caries removed using chemo-mechanical caries removal gel Carisolv^<TM> (Group 1) and for the other side of the sectioned specimens, caries was removed using a round bur (Group 2). The hardness was determined from the caries removal surface to 300μm depth toward pulp chamber wall. There was no significant difference of the KHN between Groups 1 and 2.
4). Hardness and elasticity of primary dentin measured by a nanoindentator
Hardness (H) and Young's modulus (Y) of the carious and sound primary canine dentin were measured by a nano-indentation tester. For sound teeth, the H and Y values of inner layer were significantly lower than those of outer and middle layers. The H and Y values of the under cavity area of the decayed teeth showed significantly lower than those of the regions, that were equivalent to the under cavity of the decayed teeth, on the sound side. The H and Y values of the adjacent non cavity areas of the decayed teeth also showed significantly lower tendency than those of the regions, that were equivalent to the adjacent non cavity area of the decayed teeth, on the sound teeth. Less
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