Martin Jj

Soil, Water, Food, and Teeth

“Perhaps if we forgot about dental caries for a while and just became curious about teeth and their environment we might accumulate sufficient knowledge to answer many questions.”

Biochemical Studies with Mixed Populations of Oral Bacteria

UMEROUS quantitative investigations have attempted to determine qualitatively which organisms are the causative agents of dental caries and how enamel is destroyed. Examples of such work are pH measurements of saliva, plaque material, and pure and impure cultures of oral microflora, as well as the classical plate counts for total bacteria, acid formers, and other groups. Much of this voluminous literature has been competently surveyed in 1952 and is now conveniently accessible.1 However, the constantly changing interrelationships between the mixed microfloral population as a whole and its mean, over-all, or statistical biochemistry have received much less attention. Yet this kind of dynamic approach is suggested by the variability of conditions in the mouth. While some properties (e.g., moisture and temperature) remain fairly constant, others (e.g., diet and pH) vary continuously or discontinuously. These changes may be cyclical (e.g., variation in oxidation-reduction potential) and may result from factors intimately interrelated and exerting a mutual influence upon one another. For example, bacterial action is largely responsible for the pH of the microbic milieu while pH in turn exerts a selective, directive, or otherwise controlling effect on the biochemical activities of the developing culture. Direct qualitative studies of this kind of mass population dynamics would be different from the more static and quantitative technics so far largely employed. This paper reports experiments on the cultural properties and respiratory activities of mixed populations representing different physiologic groups of oral microorganisms. The objective was more to explore the respirometric methodology for studying the metabolism of oral bacteria in mixed culture than to conduct a comprehensive biochemical investigation. Although the Warburg technic has already been used to measure oxygen consumption by salivary microflora,2-4 its general usefulness exceeds this particular purpose.