Microbiological risk for periodontitis of abutment teeth in patients with removable partial dentures.

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.