Microscopic evaluation of root surface associations in vivo

These preliminary studies were undertaken to test the effectiveness of a new procedure for in vivo examination of interactions between bacteria and root surfaces. For this purpose, four patients with juvenile periodontitis, four with chronic periodontitis, and four normal subjects were selected. For this procedure, root segments 8 mm long, 2 mm wide, and 150–200 μm thick were prepared from normal teeth extracted for orthodontic reasons. These root segments were then sterilized with ethylene oxide. In each subject, one root segment was placed in direct apposition to the mesial surface of a previously scaled lower first molar and positioned to extend 4–5 mm supragingivally and 2–4 mm subgingivally. Root strips were removed after seven days, fixed, dehydrated, and embedded in Spurr's resin. Light and electron microscopic examination of sections from the supragingival portion of root segments revealed bacteria within the root surface in all normal and chronic periodontitis subjects and in two juvenile periodontitis subjects. A nonpenetrating flora was associated with the supragingival portion of the root segments from the other two juvenile periodontitis subjects. Subgingivally, root segments from normal subjects were colonized by junctional epithelium with hemidesmosomes and wide intercellular spaces in which bacteria and polymorphonuclear leukocytes were occasionally seen. In root segments from chronic periodontitis patients, the surface appeared to be occupied by Gram (+) bacteria that were morphologically similar to those seen supragingivally in samples from the same patients. Polymorphonuclear leukocytes and a sparse, loosely associated flora was present on the surface of the subgingival portion of the root samples from juvenile periodontitis patients. The contrast between the presence of bacteria within the supragingival and subgingival portions of root segments obtained from chronic periodontitis patients and the absence of bacteria in root segments from all subgingival samples and two supragingival root samples in the juvenile periodontitis group was considered the most provocative result of the study. It was concluded, on the basis of these results, that the procedure used for the preparation and placement of root segments overcomes limitations inherent in other techniques for the study of subgingival events and permits clear discrimination between patterns of bacterial colonization of the root surface in different subject populations.