Bacterial diversity in abutment teeth of removable partial denture users

Objective: To characterize bacterial diversity by culture-independent molecular methods in supra and subgingival biofilms from abutment teeth of free-end removable partial denture users after prosthesis placement. Methods: Five women (60 to 74 y.o.) in good periodontal health were rehabilitated with a free-end mandibular removable partial denture (RPD) and a maxillary complete denture. All patients received oral hygiene instructions and motivation. Supra and subgingival biofilms from direct abutment teeth and biofilm present in RPD frameworks were collected immediately prior to (t₀), one week (t₁) and four months after (t₂) prostheses were inserted. Bacterial DNA was extracted from samples, and 16S rDNA was PCR amplified with generic primers. Amplicons were cloned into Escherichia coli. Clones were submitted to cycle sequencing, and sequences were analyzed and compared with GenBank data. £ -LIBSHUFF was used to determine if DNA libraries differed among subjects and time points (error rate of 5%). A similarity matrix constructed in DNAdist (Jukes and Cantor model) was used as the input file. Results: A total of 2197 sequences of approximately 450 bp were obtained. About 97.6% fell into 88 known species (ID≥98%). Streptococcus and Veillonella were major components of all biofilms collected. Periodontal pathogens such as Porphyromonas gingivalis and Fusobacterium nucleatum were more prevalent after prosthesis use. Selenomonas, Prevotella, Campylobacter, Capnocytophaga, Corynebacterium, Terrahaemophilus, Actinobaculum, Catonella, Eikenella, Kingella and Lachnospiraceae were also more prevalent in t₁ and t₂. In framework biofilms of t₂ the following genera were identified: Rothia, Johnsonella, Kingella, Cytophaga, Eubacterium, Porphyromonas, Candidatus, Abiotrophia, Actinomyces, Bacteroidetes, Capnocytophaga, Cardiobacterium, Eikenella, Fusobacterium and Neisseria. Conclusions: a) the bacterial diversity of supra and subgingival biofilms seemed to change after RPD use; b) the presence of periodontal pathogens in RPD frameworks suggests that it may work as a reservoir for infection and re-infection of teeth and other oral surfaces.