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Tannerella forsythia, Porphyromonas gingivalis and Treponema denticola are identified as the red complex which exists in high proportions in periodontally diseased patients. The aim of this study was to assess the microbiological risk for periodontitis of abutment teeth in subjects wearing removable partial dentures (RPDs) by measuring the red complex using BANA-ZymeTM test. Thirty-eight subjects (mean age: 62.2 years) with Kennedy Class II partially edentulous arch participated in this study. The red complex and clinical parameters, such as plaque index, gingival index, probing depth and tooth mobility were recorded at abutment teeth in contact with the direct retainer of unilaterally designed RPDs and the corresponding non-abutment teeth on the opposite side. Mean scores for the red complex, plaque index, gingival index and tooth mobility of the abutment teeth were significantly greater than those of the non-abutment teeth (P < 0.01). No significant mean difference in pocket depth was found between the abutment and non-abutment teeth. Logistic regression analysis revealed that abutment teeth, high scores of plaque index and a maintenance interval longer than 6 months were significant predictors for positive red complex scores (P < 0.05). These results suggest that the microbiological risk for periodontitis of abutment teeth is greater than that for non-abutment teeth in RPD wearers.

Biofilm formation on oral implants can cause inflammation of peri-implant tissues, which endangers the long-term success of osseointegrated implants. It has been reported previously that implants revealing signs of peri-implantitis contain subgingival microbiota similar to those of natural teeth with periodontitis. The purpose of the first part of this study was an atraumatic, quantitative investigation of biofilm formation on oral implant abutments; the objective of the second part was to investigate whether Haemophilus actinomycetemcomitans and Porphyromonas gingivalis were present in the crevicular fluid around oral implants. Biofilm formation on 14 healing abutments, inserted for 14 days in 10 patients, was analysed quantitatively by use of secondary-electron and Rutherford-backscattering-detection methods. A 16S rRNA-based polymerase chain reaction detection method was used to detect the presence of H. actinomycetemcomitans and P. gingivalis in the crevicular fluid. For this investigation, samples of sulcus fluid were collected with sterile paper points at four measurement points per abutment. The difference between biofilm coverage of supragingival surfaces (17.5 +/- 18.3%) and subgingival surfaces (0.8 +/- 1.0%) was statistically significant (P < 0.05). By use of universal primers, bacteria were found in all the samples taken, although the two periodontal pathogens were not found in any of the samples. The absence of periodontal pathogens from the sulcus fluid during initial bacterial colonization, despite massive supragingival biofilm formation, substantiates the assumption that cellular adherence of peri-implant tissue by means of hemidesmosoma, actin filaments and microvilli reduces the risk of formation of anaerobic subgingival pockets.

Thirty patients (19 men and 11 women) were provided with a removable partial denture (RPD) and assigned randomly to two groups: 15 patients were called back twice a year for plaque control, reinforcement of instructions, denture hygiene control and professional prophylaxis; the other 15 were not called back. The 30 patients were examined after 2-3 weeks following the end of the prosthetic treatment, after 1 and 2 years. At each examination, the following parameters were recorded [gingival inflammation, plaque index (Pl I), tooth mobility, attachment level, pocket depth] and a bacteriological examination of subgingival plaque was carried out. Few differences appeared between the two groups; the values observed show a relatively low level of hygiene and but little motivation with regard to prophylaxis techniques.