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Freeze‐etching and dental research
Author(s) -
Newman H. N.
Publication year - 1972
Publication title -
journal of periodontal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.31
H-Index - 83
eISSN - 1600-0765
pISSN - 0022-3484
DOI - 10.1111/j.1600-0765.1972.tb00634.x
Subject(s) - ultrastructure , cytoplasm , dental plaque , bacterial outer membrane , organelle , cell wall , microbiology and biotechnology , matrix (chemical analysis) , biology , bacterial cell structure , bacteria , chemistry , anatomy , biochemistry , genetics , escherichia coli , chromatography , gene
Dental plaque is the aetiologie factor common to caries and chronic periodontitis. Understanding of the structure of this microbial film has been hindered by the fact that conventional methods of fixation and embedding are more or less disruptive in their effects. Freeze‐etching provides a means of examining plaque at an ultrastructural level in a state more closely approximating to that existing in vivo than is possible with other methods. The technique has been applied to the study of several oral commensal bacteria. Nocardia, Bacillus subtilis and Streptococcus viridans species have been shown to possess particulate cytoplasmic membranes, more particles being present on outer than on inner aspects. The previously described pattern of the spore coat of B. subtilis is confirmed, and, as in other non‐oral species, the organisms examined appeared to possess regularly structured cell walls. The banded appearance of S. viridans is similar to that in S. mutans recently seen using scanning electron microscopy. Similar features of cell wall and cytoplasmic membrane have been observed in samples of dental plaque. Specimens resembling outer (salivary) surface plaque as prepared for conventional electron microscopy were found to contain numerous types of organism, principally coccal, in a fairly homogeneous matrix. Many cells possessed intracytoplasmic organelles. In the deeper layers, extracellular bodies were sometimes visible in the interbacterial matrix. Several types of fibrillar component were observed, passing between adjacent bacterial membrane layers, extending from the cell wall into the plaque matrix and connecting adjoining organisms. It is suggested that such fibrillar structures may be as significant in maintaining attachment of micro‐organisms to one another and to the tooth surface as any inherent stickiness of polysaccharides. Some organisms were found to be joined to one another by broad, structureless junctional zones. Many organisms possessed intracytoplasmic inclusions and cells were frequently septate.