Abstract
Carious cavities induced in fissures of 1106 Wister strain rats, from 41 groups belonging to 13 experimental projects, were recorded in respect to the prevalence (P) of caries in a group of rats, and the average extent (E) in each rat, and statistically analysed, resulting in the equation; P=0.502 log10E+0.426. This result was introduced from a differential equation based on the fact that the susceptibility differences in any two successive orders go in inverse proportion to the susceptibility order of the site. The above functional relation can be adapted for a similar treatment of human caries, i. e., Pj=0.677 log10Ej+0.495 for school children aged from 7 to 12 years. Due to the nature and ubiquity of this equation, it was considered that each result obtained on the prevalence and extent of rat caries must be corrected by it, and then the project should be discussed with these corrected values. The results of the correction indicated that a modification of the cariogenic-purified-diet (6PMV) by varying the vitamin B1 content, substitution of casein for gelatin in 6PMV, post-eruptive administration of fluoride, and modification of the calcium-phosphorous ratio to a value of 2.0 had a caries inhibiting effect offsetting cariogenicity of this diet. Here inhibition by fluoride was concluded to be based on the statistical significance of the difference between two prevalences to be compared. Inhibiting effects of vitamin B1 and gelatin were concluded depending on the mode of action when an increasing amount lineally decreased prevalence as well as the logarithmic value of extent. Correction of obtained results and consideration of the mode of action of each agent will be a starting base for biological standardization. Another benefit in the correction of obtained results is that even if the scoring unit is changed it never causes an inverse effect. In the statistical treatment, the significance of the difference of the results have validity only when prevalences (P) are compared in the range less than 1, and the average logarithmic extents (E) of two groups are compared in the range P=1.
