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The reliability of a paralleling instrument for dental radiographs was retrospectively evaluated in the course of a 6-month clinical study. The angular variation between successive exposures was precisely quantified. Ninety-one percent of the angular variations were below a 1.4 degree threshold, but some paired images were found unsuitable for quantitative analysis. A mathematic procedure to assess the global angular projection error of any similar coupled x-ray cone-film holder device is proposed. This mathematic procedure should be routinely used to check superimposability of serial radiographs before density quantification or subtraction.

The four maxillaryincisors and two maxillary premolars of a 25‐year‐old male patient were used to study epithelial and connective tissue attachment 67 days and 164 days after flap surgery and cutting of an horizontal intradentinal groove near the buccal cervical region. Three teeth were topically conditioned for 3 minutes with citric acid pH = 1. The three other teeth were used as controls. The histologic examination was carried out in doubleblind conditions; the examiners did not know which specimens were acid treated until the end of the study. Two of the three cases treated with citric acid showed improved healing conditions, when compared to the controls; a more coronal position of the epithelial attachment in the dentin nick as well as a relatively important gain in connective tissue attachment. Two types of connective tissue attachment were observed. The first consisted of an attachment to dentin, without cementum formation and was characterized by a mineralization of decalcified dentin collagen spliced with collagen, newly secreted by fibroblasts. The second type involved cementum formation. Topical citric acid treatment, however, can not be considered as a completely reliable clinical procedure since in one experimental case the type of attachment observed was not better than that seen in the control.

The concentration of alpha 2-macroglobulin (alpha 2-M) in human gingival sulci has been investigated in two studies: first, in gingival washings during a 21-day period of experimental gingivitis in eight human volunteers and, second, in crevicular fluid collected with filter paper strips before and after initial periodontal therapy in 11 patients. The concentration of total alpha 2-M was found to increase in the washings of the volunteers throughout the period of experimental gingivitis. In the group of patients receiving periodontal therapy, the absolute amount of alpha 2-M in the fluid showed a significant decrease after therapy. The gingival index of inflammation and the crevicular fluid flow also decreased significantly. The specific content of the inhibitor (micrograms of alpha 2-M per mg of fluid per min), however, was found to increase in the fluid with decreasing inflammation. As detected by crossed immunoelectrophoresis, the fluid collected in these patients before therapy, in the presence of severe inflammation, invariably showed peaks of both free and complexed alpha 2-M. In contrast, the fluid collected from the same sites after healing of the inflammation contained no detectable free alpha 2-M.

Samples of hydroxyapatite (HA) beads smaller than 1 mg were coated with 10 microliter of either saliva, serum, or human crevicular fluid before being added to a suspension of Streptococcus sanguis or Bacteroides gingivalis. In some assays, preparations of a granular fraction, elastase, or cathepsin G from human leukocytes were used to coat HA or to treat saliva-coated HA (SHA) before mixing with bacteria. The number of cells adhering to the beads was then counted under a scanning electron microscope by a standardized procedure. More cells were found to adhere to SHA in this assay than in the conventional large-scale assay. Human crevicular fluid, even when diluted up to three times, completely inhibited the adherence of S. sanguis to HA. A 100% inhibition of S. sanguis adherence was also observed when HA was coated with the granular fraction of leukocytes, and a 65% inhibition observed when SHA was treated with the enzyme preparation. When used to coat HA, elastase and cathepsin G reduced the adherence of S. sanguis by 30 and 50%, respectively. The binding of S. sanguis to elastase- or cathepsin G-treated SHA was also reduced. B. gingivalis 33277 was found to adhere in high numbers to SHA. Coating HA with crevicular fluid or with the lysosomal enzyme preparation had a limited negative effect. We postulate that crevicular fluid prevents the adherence of S. sanguis by virtue of either its enzyme content or its albumin content or both.