Microhardness of carious deciduous dentin.

The purpose of this study was to measure the microhardness values of deciduous dentin and to compare the values as a function of position in the caries-affected layers of dentin including transparent, adjacent sound dentin, and dentin regions far from and not related to caries. Seven extracted or exfoliated deciduous anterior teeth that had dentin caries on a proximal surface were sectioned parallel to the long axis of the tooth. Ten sectioned and polished specimens were dehydrated and dried. Microhardness was measured with a Knoop indenter and correlated with wet-SEM micrographs. All data were statistically analyzed using a two-way ANOVA with subsequent Tukey-Kramer multiple comparison tests at p < 0.05. The hardness decreased from the dentinoenamel junction to the pulp chamber wall, except for the region under the caries. The hardness values of the region under the caries were significantly lower than those of other regions except for the inner region. For both the carious and sound sides, the hardness values of the inner region were significantly lower than those of the outer and middle regions. In comparing the hardness among regions in the carious and sound sides, the hardness of the outer, middle, and inner regions on the carious side was significantly lower than those in the sound side.