An assessment of recent advances in the study of the chemistry and biochemistry of dental plaque fluid.

This paper discusses key points made during the symposium in the light of work carried out in other laboratories. It is emphasized that the unique importance of plaque fluid is that the net result of chemical changes induced by microbial activity is reflected in this medium, which is in intimate contact with the enamel surface, and that this medium is accessible to chemical and biochemical analyses. However, in order to assess the cariogenic potential of plaque, we must consider the properties of both whole plaque and plaque fluid together. Although it is apparent that results of plaque fluid composition are sensitive to both isolation and the storage procedures utilized, plaque fluid appears to be a distinct entity within the oral cavity. Technical advances have been made which allow for the determination of the activity of selected ions (hydrogen, calcium, phosphate, potassium, fluoride) in plaque fluid obtained from a single site within the mouth. It appears, however, that such data alone may be insufficient to define the cariogenic potential of plaque appropriately. Evidence is presented from which it can be concluded that, with use of pooled samples of plaque obtained from individuals with clear differences in caries experience, results on plaque and plaque fluid composition can be obtained which are consistent with noted differences in caries susceptibility. The importance of base production is also discussed, and it is noted that few studies have been carried out to elucidate the role of proteins found in plaque fluid. In conclusion, recent advances in the study of plaque fluid have provided new insights into the mechanism of caries formation which are also germane to the formation of dental calculi.

Assessment of the validity of two plaque indices.

The validity of the Podshadley and Haley Patient Hygiene Performance Index (PHPI) and the Silness and Löe Index (PlI) was investigated. Fifty children aged 11-12 years were examined by a single examiner and plaque collected from all accessible smooth surfaces, and dry weight determined. Statistically, there were significant positive correlations between plaque dry weight and PlI (r = 0.61) & PHPI (r = 0.63). The results indicate that both indices were equally good indicators of the amount of plaque on accessible smooth surfaces.