Electron-microscopic Observations on Soft Carious Human Dentin

In the process of dentinal caries both the organic and the inorganic components of the tissue are ultimately destroyed and eliminated, with resulting cavitation. Since ultrastructural studies of dentin in various stages of decay should almost certainly contribute importantly to a better understanding of the carious process, an electron-microscopic survey of carious dentin was undertaken in our laboratories. A number of papers have already appeared dealing with electron-microscopic observations on both artificially demineralized and undecalcified carious dentin. The distribution of micro-organisms in the carious lesionl-5 and the presence of typical cross-striated collagenous fibrils in the matrix1' 2 have been described. Lenz6 found large calcified bodies in dentinal canals, but, to our knowledge, no detailed information concerning the mineral phase of carious dentinal matrix has been reported. This paper deals with soft carious dentin presumed to be in an advanced state of decay. The character and distribution of the mineral moiety (apatite crystallites) of carious dentinal matrix are described. Dense mineral deposits lacking a collagenous matrix are also reported at the periphery of the dentinal canals. Finally, the appearance of the collagenous fibrillar component of carious dentinal matrix is described as it appears in sections stained with phosphotungstic acid and in homogenized tissue. The implications of certain of these findings as they relate to the carious mechanism are discussed.