Comparability and discriminating power of 4 plaque quantifications

Clinical models that objectively evaluate interproximal plaque based on total protein concentration

AIM

To establish clinical models that accurately and objectively assess the levels of interproximal plaque (IPP) by measuring the total protein concentration.

MATERIAL AND METHODS

The multiple treatment (MTM) and single-treatment models (STM) were designed as randomized, double-blinded, crossover studies whereby IPP was collected using floss. The total protein concentration in the plaque was then measured using a fluorescence microplate assay. To demonstrate sensitivity, the levels of residual IPP were compared for two distinctly different plaque removal routines: brushing versus brushing+flossing.

RESULTS

Eighteen subjects completed the study for the MTM, while 16 participants completed the study for the STM. The results showed that both models were able to distinguish between treatments. Moreover, fundamental profiles were established that describe the mean changes in the IPP concentration over time and by treatment. Finally, a comparison between our results and a direct measure of IPP, i.e., plaque weight, demonstrated the potential of using protein as a quantitative means to assess IPP levels.

CONCLUSION

The MTM and STM provide an objective, quantitative assessment of IPP based on the total protein concentration in plaque.

Quantification of dental plaque on lingual tooth surfaces using image analysis: reliability and validation

AIM

The aim of this study was to increase the versatility and further validate the method reported by Smith et al. (2001) by testing the reliability of plaque measurement against two well-known dental plaque quantification methodologies using image analysis in a clinical trial.

METHOD

The teeth of 40 subjects were disclosed before digital images of the labial and lingual surfaces of their upper and lower incisors were acquired. The amount of plaque present was quantified using a modification of the method described by Smith et al. (2001). The method was modified for obtaining images of the lingual surfaces by incorporating the use of orthodontic occlusal mirrors and 5-mm pieces of moistened blue articulating paper used to enable calibration. Plaque measurements were made from 320 upper and lower anterior teeth from the 40 subjects by two operators. Fliess' coefficient of reliability was used to assess intra- and inter-operator reliability and the independent sample t test was used to assess statistical significance between test and control groups after checking the data for normality. For validation, measurements were recorded using the Turesky et al. (1970) (modification of the Quigley & Hein (1962) plaque index and the Addy et al. (1983) plaque area index. The results were compared with the image analysis method using Pearson's correlation coefficient.

RESULTS

The results for reliability were within Fliess' range of "excellent" for both intra-operator repeatability and inter-operator reproducibility. Pearson's correlation coefficients showed highly significant values indicating the close similarity between all three methods.

CONCLUSIONS

This method for the measurement of dental plaque on lingual surfaces of anterior teeth proved reliable. The combined results from the labial and lingual surfaces of anterior teeth using image analysis produced trial conclusions comparable with the alternate plaque quantification methods used, with less clinician time and further producing a permanent database of images for future use.

Patterns and rates of growth of microcosm dental plaque biofilms

Rates of growth in wet weight and changes in them over time were established for microcosm dental plaques cultured from the mixed salivary bacteria in an artificial mouth. Standardized conditions included a continuous supply of medium containing 0.25% mucin and 1.5 ml of 5% w/v sucrose in 6 min every 8 h. Plaques were weighed daily. Plaque wet weight and total protein were highly correlated. Plaque doubling times were 3-7 h over day 1 and 9-21 h over day 2, which is similar to in vivo plaques. Subsequently, growth curves were either linear or between a linear and exponential increase. Evidence was obtained for plaque blooms. Methyl paraben (0.2%) applied for 15 min (3.75 ml) 6 times daily inhibited growth but only for 3 days, after which the rate was similar to control plaques, indicating that selection for resistance had occurred. It was concluded that the regulation of plaque growth rates is complex and does not conform to simple growth pattern models. Detailed studies of plaque growth and the effects of antiplaque agents can be carried out using this experimental system.