Comparison of microbial changes in early redeveloping biofilms on natural teeth and dentures

Abstract

Background: Surfaces and fluids can affect oral bacterial colonization. The aim of this study is to compare redeveloping biofilms on natural teeth and dentures.

Methods: Supragingival plaque samples were taken from 55 dentate individuals and the denture teeth of 62 edentulous individuals before and after professional cleaning. Also, samples from seven "teeth" (samples included dentures) in randomly selected quadrants were collected after 1, 2, 4, and 7 days of no oral hygiene. Samples were analyzed using checkerboard DNA-DNA hybridization. Counts and proportions of 41 bacterial taxa were determined at each time point, and significant differences were determined using the Mann-Whitney U test. Ecological succession was determined using a modified moving window analysis.

Results: Mean total DNA probe counts were similar precleaning but were higher in dentate individuals at all post-cleaning visits (P <0.01). Precleaning edentate biofilms had higher counts and proportions of Streptococcus mitis, Streptococcus oralis, and Streptococcus mutans, whereas dentate individuals had higher proportions of Tannerella forsythia, Selenomonas noxia, and Neisseria mucosa. By day 2, mean counts of all taxa were higher in natural teeth, and most remained higher at day 7 (P <0.01). Succession was more rapid and complex in dentate individuals. Both groups demonstrated increased proportions of S. mitis and S. oralis by day 1. N. mucosa, Veillonella parvula, and Eikenella corrodens increased in both groups, but later in samples from edentate individuals.

Conclusions: "Mature" natural and denture teeth biofilms have similar total numbers of bacteria but different species proportions. Post-cleaning biofilm redevelopment is more rapid and more complex on natural teeth than on denture teeth.

Conflict of interest statement

The authors have no conflicts of interest.

Figures

Fig. 1

Mean % of the total DNA probe counts of 41 bacterial taxa in samples taken from 55 subjects with natural teeth and 62 subjects with full mouth dentures. Significance of differences in mean species proportions between groups was determined using the Mann Whitney test; # p

Fig. 2

Mean total DNA probe counts (× 105, ± SEM) of supragingival biofilm samples taken at entry (pre-cleaning), immediately post-cleaning and after 1, 2, 4 and 7 days of biofilm development. Significance of differences between clinical groups at each time point was determined using the Mann Whitney test. The bars represent mean total DNA probe counts and the whiskers the SEM at each time point.

Fig. 3

Cumulative mean counts (× 105) of 41 bacterial species in samples taken from 55 subjects with natural teeth and 62 subjects with full mouth dentures. The plots present the cumulative mean values at each time point in each clinical group. The species were ordered and color-coded according to previously described microbial complexes (Socransky et al. 1998) .

Fig. 4

Mean counts (× 105) of 41 bacterial species in samples taken from 55 subjects with natural teeth and 62 subjects with full mouth dentures. Significance of differences in mean species counts between groups at each time point was determined using the Mann Whitney test; # p < 0.05, ** p < 0.01, †† p < 0.001. The species were ordered according to previously described microbial complexes (Socransky et al. 1998) .

Fig. 5

Bar charts of the mean % of the total DNA probe count of 41 bacterial species in samples of biofilm taken immediately after tooth cleaning and after 1, 2, 4 and 7 days of biofilm accumulation in the absence of oral hygiene procedures. Samples were provided by 55 dentate subjects (left set of bars in each panel) and 62 subjects with upper and lower full dentures (right set of bars in each panel). The red bars indicate a significant increase in the mean proportion from a mean value for an earlier time point for that species in that clinical group. In a similar fashion, the blue bars indicate a significant reduction in mean proportion of a species from an earlier time point.

Fig. 6

Grid plot summarizing significant increases (red rectangles) in mean proportions of bacterial taxa in biofilm samples obtained from 55 dentate subjects and 62 edentulous subjects who wore full dentures. The data were derived from Fig. 5. The red rectangles indicate a significant increase in mean proportion of that species from mean proportions of that species at an earlier time point. The species were ordered according to the order of significant increases in mean proportions of species in the dentate subjects.