Electron-microscopic Observations on Soft Carious Human Dentin

Abstract

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. MATERIALS AND METHODSPermanent human teeth with apparently active carious lesions were obtained from the Dental Clinic of Strong Memorial Hospital, Rochester, New York. The whole teeth or soft carious materials excavated from carious lesions were fixed immediately after operative removal in cold (40 C.) 1 per cent osmic acid solution containing sucrose (0.22 M) and buffered to pH 7.2-7.4 with 0.025 M veronal acetate buffer, in neutral 10 per cent formalin, or in 70 per cent alcohol. Some of the material was dehydrated in alcohol and imbedded in butyl methacrylate catalyzed with 1 per cent benzoyl peroxide. Some material was stored in 70 per cent alcohol and sectioned without further treatment. A few observations were also made on fresh, untreated tissue. Sections were cut with a microtome* equipped with a glass knife.

Human Root Caries: Histopathology of Advanced Lesions

“…21-23, insets 1-3). This is in accordance with several previous TEM [Johansen and Parks, 1961;Symons, 1970;Frank and Voegel, 1980] and SEM [Mendis and Darling, 1979;Jones and Boyde, 1987] studies conducted on coronal caries. There is, however, some disagreement on the crystal formation.…”

The Response of Deciduous Dentine to Caries Studied by Correlated Light and Electron Microscopy

“…Remnants of densely min eralised tissue are usually present in bacteria-filled tubules, usually at the periphery but occasionally more centrally. The crystal structure is similar to that seen in Type I mineralisation and these areas presumably represent residues of sclerosed tubule content or of peritubular dentine [Johansen and Parks, 1961;Symons, 1969], In these areas the intertubular dentine is extensively demineralised. Typical banding is still present on collagen fibres and this has been inter preted by several authors as suggesting that the organic matrix of dentine is more resistant to caries than the mineral component (for example, Jo hansen, 1963).…”

Remineralization of Bovine Incisor Root Lesions in vitro: The Role of the Collagenous Matrix

“…Protection of mineral dissolution by organic matrix components may be a key factor to understand and/or achieve remineralization and arrestment of dentinal lesions. In a more advanced stage of the caries process, the ap parently firmly bound mineral disappeared more or less simultaneously with destruction of the collage nous matrix [Johansen and Parks, 1961;Frank et al, 1964;Selvig, 1968]. In cementum caries, an almost synchronous breakdown has been demonstrated of the inorganic and organic components [Furseth, 1971;Frank et al, 1989].…”