Streptococcus mutans and Streptococcus sobrinus biofilm formation and metabolic activity on dental materials.

OBJECTIVES: To examine potential correlations between streptococcal biofilm formation and lactate production in streptococcal biofilms formed on the surface of dental materials with different surface characteristics. MATERIALS AND METHODS: Samples of a glass-ionomer cement (Ketac Molar) and a ceramic (Empress 2) were incubated with whole saliva and suspensions of Streptococcus mutans ATCC 25175 or Streptococcus sobrinus ATCC 33478 for initiating single-species biofilm formation for either 4 or 24 h. The relative amount of adherent, viable cells was determined using a Resazurin and a MTT assay. Metabolic activity was assessed by quantifying lactate production with a modification of the commercial Clinpro Cario L-Pop kit. RESULTS: Both assays identified similar S. sobrinus biofilm formation on the two substrata; for S. mutans, the MTT test showed significantly fewer streptococci on the glass-ionomer cement than on the ceramic. Concerning metabolic activity, for S. sobrinus, significantly higher lactate production was observed for biofilms formed on the glass-ionomer cement in comparison to the ceramic, whereas similar values were identified for S. mutans. CONCLUSIONS: Within the limitations of the study, the results suggest that the pure amount of adherent streptococci does not a priori indicate the metabolic activity of the cariogenic bacteria organized in the respective biofilm. Thus, comparisons between the relative amount of adherent streptococci and their metabolic activity may allow for an improved understanding of the effect of dental material surfaces on the formation and metabolic activity of streptococcal biofilms.

Determination of caries risk at resin composite margins.

PURPOSE: To design an artificial mouth in order to evaluate if a new diagnostic tool (Clinpro Cario Diagnosis) can be used for early detection of secondary caries at resin composite margins in vitro. METHODS: 32 intact human third molars received standardized Class-V resin composite restorations (Tetric Ceram bonded with Syntac SC). After storage for 4 weeks at 37 degrees C, teeth were subjected to 5,000 or 10,000 thermocycles (+/- 5 degrees C and +/- 55 degrees C) and polysiloxane impressions were taken. Streptococcus mutans 10449 (SM) was used in a nutrition medium to initiate a secondary caries process. Daily, the teeth were incubated for 2 x 2.5 hours in SM containing nutrition medium followed by 2 x 9.5 hours incubation in artificial saliva. Teeth were investigated after total incubation periods of 4, 6, and 8 weeks. After the different incubation protocols, the restoration margins were evaluated for infection and secondary caries processes in using Clinpro Cario Diagnosis which measures site-specifically the lactic acid production of SM in response to a sucrose challenge. The color signal was read 5 minutes after removal of the diagnostic impression. After thermocycling and biological load cycling, precision polysiloxane impressions were taken and replicas were investigated under a light microscope for gap widths at enamel and dentin margins. Demineralization was evaluated by fluorescence microscopy in using a special FITC filter. The demineralization depths at the cavity margin were calculated with Xpert for Windows using a pixel distance of 5 microm. RESULTS: After the different thermocycling protocols, no differences in gap widths and demineralization depths were found (P > 0.05). After SM incubation, gap widths and demineralization depths were significantly dependent on SM incubation time and previous number of thermocycles (P < 0.05). Lactic acid formations of SM were detectable by Clinpro Cario Diagnosis at dentin cavosurface margins formed after 6 weeks of incubation with SM (P < 0.05).

Subgingival plaque removal at interdental sites using a low-abrasive air polishing powder.

BACKGROUND: The aim of the study was to test the efficacy of a novel low-abrasive air polishing powder in subgingival plaque removal at interdental sites during periodontal maintenance therapy (PMT). METHODS: Using a split mouth design, subgingival plaque was removed in 23 PMT patients using a low abrasive powder using a standard air polishing unit (test) or curets (positive control). Before and immediately after treatment, subgingival plaque samples were taken from interdental sites with 3 to 5 mm probing depth (PD) at 2 test teeth and 2 positive control teeth. To evaluate the influence of sampling on the microflora, plaque samples were also taken twice at 2 teeth without therapy with PD of 3 to 5 mm (negative control). PMT treatment and plaque sampling were repeated 3 times at quarterly intervals. Anaerobe cultivation was utilized to assess the mean reduction of total colony forming units (CFU) immediately after treatment. RESULTS: Test treatment resulted in a significantly greater reduction in subgingival bacterial counts (log 1.9 +/- 0.7) than positive control treatment (log 1.1 +/- 0.6) and subgingival plaque sampling alone (log 0.5 +/- 0.5; P < 0.05). Differences between positive and negative control were not significant (P < 0.05). CONCLUSION: The novel low-abrasive air polishing powder is superior to curets in removing subgingival plaque at interdental sites with up to 5 mm probing depth in PMT.