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A well known development of the chronic periodontal disease is reviewed. However, the histological picture of gingiva varies at a much lower speed than its clinical picture, and slower than previously described. In presence of periodontitis there may exist a zone of reversible disease of about 2 mm, which gives the possibility of obtaining a re-attachment of unknown magnitude. A new connective tissue attachment (on top of the re-attachment) seems only possible if the periodontal ligament cells are allowed to proliferate coronally.

In the western countries, the acute necrotizing gingivitis occurs mainly in early adulthood. It is characterized by a marginal necrosis of the gingiva. The papillae appear to be punched out. The gingiva is painful and bleeds, and the patient often presents halitosis. This fusospirochetal infection invades the epithelium and the underlying connective tissue in its most superficial layer. With early acute necrotizing gingivitis, the use of chlorhexidine 0.2% is recommended, but a thorough scaling is still necessary. Antibiotics are used when the disease becomes more severe. Gingivoplasty may be required at the end of the treatment but a meticulous oral hygiene is the only way to prevent any recurrence of the disease.

Within the framework of a gingivitis study the sulcus fluid flow rate (SFFR) at the lower and upper premolars of 9 subjects was determined with the assistance of Periotron 6000. The measurements were conducted at days 0, 7, 14 and 21 with the aim to compare the SFFR after 3 minutes (Löe and Holm-Pedersen 1965, Rüdin et al. 1970) with the measurements of Lamster et al. (1985a, b) at 30 seconds. The increase of the SFFR at 30 seconds, as well as at 3 min was significant on all measurement days, but no proportional dependance of SFFR on the measurement time was seen. On the basis of these results it is justified to restrict the SFFR to 30 seconds, to reliably determine the grade of infection of gingiva.

The influence of oral hygiene on early plaque formation has been studied. The amount and structure of dental deposits formed on plastic films were determined at two occasions with or without a preceding period of effective oral hygiene. Six human subjects developed plaque during 4 hours on plastic films applied to the buccal surfaces of premolars and cuspids. The plastic films with adhering deposits were processed for electron microscopy. In presence of healthy gingiva, the plastic films were covered by a surface coating of acellular material in or on which bacteria, epithelial cells and leukocytes were observed. The microorganisms were almost exclusively Gram-positive cocci. When plaque formation was preceded by a week of excluded oral hygiene, the deposits collected on the same teeth exhibited a threefold increase in the number of bacteria. The relative composition of the flora was altered, as evidenced by a higher number of Gram-negative cells as well as the occurrence of rods and filamentous organisms. The results indicate that neglect of oral hygiene favors an earlier establishment of a complex bacterial flora at the dento-gingival region of the buccal surfaces of premolars and cuspids.

In radiology a sufficient diagnostic accuracy must be obtained with a minimal radiation dosage to which the patients are exposed. In-vitro studies designed to evaluate the influence of technical parameters on the quality of images on Kodak Ektaspeed and Kodak Ultra-Speed dental radiographs are presented. The following series of experiments were performed: 1. Evaluation of the Minray dc, Soredex and Oralix 65, Philips X-ray machines. 2. Comparison between two different Oralix 65 machines. 3. Evaluation of automatic and manual film processing as well as film-focus distances of 30 cm and 39 cm. 4. Evaluation of pairs of radiographs and their subtraction images obtained from different film and X-ray machine combinations. A dried mandible with and without bone splits within the central X-ray beam area on the alveolar crest between the teeth 46 and 47 served as object for the standardized images. A blind comparison of the series of images was performed by 3 certified periodontists. Irrespective of the film type used the highest rankings were given to the Oralix 65 X-ray machine, when the films were exposed at 39 cm from the focus and the automatic processing mode was used. X-ray images with good anatomical and technical details may be obtained on Ektaspeed and Ultra-Speed films. However, preference must be given to Ektaspeed films because of the possibility of reducing the radiation exposure.

The effect of chlorhexidine on early plaque formation was studied in vivo in order to assess potential structural and quantitative changes. 3 subjects with healthy gingiva were used. Plastic films were applied to the buccal surfaces of the maxillary right first premolars and plaque was allowed to form for either 4 or 24 h. A single 1-min rinse with 0.2% chlorhexidine digluconate was used for the 4-h experiments, 1 min after film placement, whereas, for the 24-h experiments, an additional 1 min rinse was used at 12 h. In total, 62 films were obtained, half treated and half controls. These were processed for light and transmission electron microscopy, using standardized techniques for area sampling and cell counting. All plastic films were covered by a surface coating of acellular material in or on which bacteria, epithelial cells and leukocytes were observed. In the controls, an important increase in bacterial count was seen between 4 and 24 h, whereas the increase with chlorhexidine was slight. There were fewer bacteria in the chlorhexidine as compared to the water specimens, for both time periods. Many microorganisms in the chlorhexidine samples appeared to be undergoing degeneration with coagulated cytoplasm and disrupted cell walls.

A well known development of the chronic periodontal disease is reviewed. However, the histological picture of a gingiva varies at a much lower speed than its clinical picture, and slower than previously described. In presence of periodontitis there may exit a zone of reversible disease of about 2 mm, which give the possibility of obtaining a re-attachment of unknown magnitude. A new connective tissue attachment (on top of the re-attachment) seems only possible if the periodontal ligament cells are allowed to proliferate coronally.

The influence of water, glucose and sucrose rises on early plaque formation has been studied. The amount and structure of dental deposits formed on plastic films were determined on four occasions: no rinsing, water, glucose or sucrose rinses. Five subjects with healthy gingiva developed plaque in 4 h on plastic films applied to the buccal surfaces of premolars and canines, after which period the plastic films with adhering deposits were processed for electron microscopy. Sections were prepared for examination in the light and electron microscope. Some were stained for the demonstration of carbohydrates according to the periodic acid thiocarbohydrazide osmium tetroxide technique. Furthermore, the number of cellular elements collected on the films during the four experiments was calculated and statistically compared. The results in the four groups were identical. The plastic films were covered by a surface coating of acellular material in or on which bacteria, epithelial cells and leukocytes were observed. The microorganisms were almost exclusively Gram-positive cocci. Many bacteria exhibited intracellular polysaccharides. The results indicate that the rinsing procedure does not influence early plaque formation, and that frequent mouthrinses with glucose or sucrose have no detectable effect on plaque growth at this initial stage of bacterial adherence.

During six month of abolished oral hygiene and concomitant development of gingivitis, the buccal subgingival microbiota was studied by darkfield microscopy as well as by cultural methods. Five dental students gave written informed consent and participated in this trial. In darkfield microscopy there was a slow reduction in the proportion of coccoid forms concomitant with an increase in the proportion of rods, while spirochetes were rarely detected during the entire experimental period. However, the cultural data revealed a decrease of the Gram-positive facultative and an increase of the Gram-negative anaerobic microorganisms after 6 months of abolished oral hygiene. The bacteriological data show, that in buccal sites--even after 6 months of abolished oral hygiene--the subgingival microflora reflects a population typical only for an initial lesion.

During 21 days of abolished oral hygiene and developing gingivitis the microbial changes were studied in buccal and interdental sites. The subgingival plaque of 6 dental students was analyzed by darkfield microscopy. The microbiota found in interdental sulci showed a higher complexity than that of buccal sites. Buccally and interdentally there was a significant increase in the total number of microorganisms between days 0 and 21. Yet, the development of gingivitis was slower in the buccal than in the interproximal sites. For all bacteria, but specially for more disease-associated morphotypes the accumulation rate was higher interdentally than buccally.