Is the Salivary Lactobacillus Count a Valid Index of Activity of Dental Caries? ∗

Abstract

Lactobacillus counts are used widely as an index to the activity of tooth decay. Much of the current philosophy relating to the cause and control of dental caries is based on the premise that the Lactobacillus count of the saliva provides a dependable prediction medium as to whether the individual in question is likely to develop tooth decay within the reasonably near future. Yet few studies have been reported wherein Lactobacillus counts have been correlated individually with the previous and subsequent progress of tooth decay over long periods of time for large numbers of subjects. Studies of that type are needed to show the validity of the Lactobacillus count as a diagnostic or prognostic agent. The study reported herewith was designed to supply evidence as to the significance of the Lactobacillus count to the individual subject.

As a part of a larger and more general survey, the Lactobacillus counts from the saliva of 64 teen-aged girls have been compared with the progression of tooth decay observed for not less than 30 months for each individual subject. The data include 407 separate Lactobacillus counts. The dental examinations were made recurrently from July, 1946 to January, 1949; the Lactobacillus counts were made on successive occasions from March, 1948 until January, 1949. The State Hygienic Laboratories made the bacterial counts, as a part of the service they provide to the dentists of the state for clinical diagnosis and prognosis.

Generally speaking, there was a slight trend toward parallelism of the Lactobacillus counts and rates of progression of caries when massed data were used. However, when the group as a whole was subdivided according to the rate of caries progression, there was little difference between the range of Lactobacillus counts observed among those with the least and those with the greatest progression of tooth decay.