Abstract
A rat marked in its dentin by some bone or tooth marker during the dentinogengtic studium, being exposed to the caries producing diet after weaning would be useful to estimate the depth of the carious lesion and the effect of factors to influence dentinal calcification. The results from experimental caries produced on this Pb-marked rat will bring some more favor for caries research. Working on such rat tooth, on the other hand, rat dentin marked by Pb injection must not exert any effect on general growth of the rat and developement of the carious lesion.
About half of total 143 Wister rats, obtained from two females and 8 males were injected with aqueous solution of Pb-Na2-EDTA at 10th, 12th, 14th days after birth. After weaning, all animals were challenged by the caries-producing diet, 6PMV, for 90 days. Both groups, Pb-marked and control, were compared with respect of average number of produced occlusal cavities or lesions and body weights. Thereafter, tooth was decalcified in the decalcifying solution saturated with H2S and sectioned for the microscopic examination.
The slightest differences of average lesions and body weights in both groups at the end of experiment were found but proved to be insignificant by statistical treatment (Fig. 1). Three black lines marked by Pb injection were usually found in dentin under a microscope (Fig. 2). In few cases, however, part of the lead-lines disappeared discontinuously at the bottom of fissure (Fig. 3-A). The deepest front of bacterial invasion of one dentinal tubule reaches extremely profound but at the nearest tubule, it appears almost inaffected. Therefore, instead of primal assumption, the degree of invation by carious attack could not estimate by these lines. However, this rat could be useful tool for the study of carious lesion and resistance of dentin against cariogenic agents, when they were added during two EDTA-Pb injections.
Much stress was placed on the findings at the lead lines which would not receive any visible affection by bacterial invasion (Fig. 3-B). Final disscussion on this findings will appeared on the succeeding report.
