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The aim of this experimental gingivitis study was to determine the subgingival microbiota in young (18 to 30 years) and older (46 to 77 years) healthy adults by darkfield microscopy and quantitative real-time PCR. Analysis by PCR focused on the total bacterial counts and on six parodontopathogenic bacteria (Aggregatibacter actinomycetem comitans, Porphyromonas gingivalis, Prevotella intermedia, Camphylobacter rectus, Dialister pneumosintes und Parvimonas micra). Subjects received professional tooth cleaning and oral hygiene instruction over a period of three weeks. At baseline clinical data were recorded and samples were collected for microbiological analysis. Subjects were then instructed to avoid any form of oral hygiene during 2 weeks. Examinations were repeated on day 8 and 15. At the end of the study, all subjects received professional tooth cleaning. The following parameters were recorded at 4 sites per tooth (mesial, distal, buccal, lingual): plaque index (Silness &; Löe 1964), gingival index (Löe & Silness 1963), periodontal probing depth and bleeding on probing. For darkfield microscopy analysis gingival crevicular fluid was collected from mesial sites of the upper incisors and upper first premolars. For PCR analysis gingival crevicular fluid was collected at three arbitrary sites.
In both age groups a significant increase in plaque index, gingival index and bleeding on probing was observed during experimental gingivitis. No significant differences were found between age-groups for clinical parameters at any experimental period. Analysis by darkfield microscopy showed an significant decrease of coccus and a significant increase of mobile rods, spirochetes, filaments and fusiformes in both age groups. The increase of mobile rods was significantly higher in the older age group. PCR analysis showed an increase of total bacterial counts and of the amount of Aggregatibacter actinomycetemcomitans, Prevotella intermedia, Parvimonas micra und Dialister pneumosintes. The increase of Aggregatibacter actinomycetemcomitans was higher in the younger age group, while Prevotella intermedia and Parvimonas micra increased higher in the older age group. However, these differences between the groups did not reach significance. The amount of Dialister pneumosintes and Porphyromonas gingivalis showed no differences between the younger and the older group. At baseline examination Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis and Parvimonas micra were only detected in the older group, which was statistically significant for Porphyromonas gingivalis.
In summary, all clinical parameters were significantly increased following 14 days of experimental gingivitis. The amount of parodontopathogenic bacteria differed between the younger and the older age group. It seems that Aggregatibacter actinomycetemcomitans appears in higher amounts in the younger age group, while Porphyromonas gingivalis, Prevotella intermedia und Parvimonas micra are increased in the older age group. Studies with more probands are necessary to prove this tendency.