A Cohort Study on Interdental Space and Interproximal Caries in Deciduous Teeth, by Neighboring Age

Abstract

This study was made to investigate the connection between interdental space and interproximal caries in the deciduous teeth by means of “neighboring age” as defined by the author. The materials were the same infants and children of 0, 1, and 2 years of age in 1965 in Kameoka City, Kyoto, on which the “Studies on Epidemiological Patterns of Caries Attack in Deciduous Teeth” had been made by means of cohort survey by the author.Interdental spaces were examined at the semiannual oral examinations by inserting a wire (diameter: 0.5mm) between two contiguous teeth and noting “Space” where the wire passed and “Contact” where it did not.Neighboring age: Considering that the neighboring relationship is formed between two tooth surfaces by the eruption of a tooth next to an existing tooth, the neighboring age was counted from this point and by half years. Furthermore, because the neighboring relationship may change as time elapses, the calculation was made only with the tooth surfaces which remained spaced or in contact according to the basis shown in Table 1. The numbers of the “contact” and “space” tooth surfaces were as shown in Table 2.Table 3 shows the caries indexes of the “Contact” group and the “Space” group: that is, caries incidence rate of tooth surfaces during a half year (Mx), number of tooth surfaces newly attacked by caries per initial healthy 1, 000 surfaces during a half year (Cx), and cumulative number of carious tooth surfaces per initial healthy 1, 000 tooth surfaces (ΣCx).The polygonal lines of Cx are shown in Fig. 1, and the trend-lines of Cx, ΣCx, and e-kx line of the proximal surfaces of Contact and Space groups obtained from Table 3 are as shown in Fig. 2.Table 4 shows the angle formed by the e-kx line and the 1-line, and the neighboring age at which the Cx trend-line reached the summit, and ΣC2.5.The trend-lines of ΣCx of proximal surfaces of the opposing tooth in the case of the spaced condition is seen in Fig. 3, while Fig. 4 shows the ΣCx trend-lines of caries in the opposing proximal surfaces in the contact condition. Of these the trend lines of almost simultaneously erupted pairs of teeth, such as A-B, C-D, A-B, and C-D are almost identical. On the other hand, in the case of D-E and D-E, if one of the pair, that is, D or D, eru- pts about a year before the other, there would be affected cases before any neighboring relationship comes to exist, and D, therefore, shows higher rates than E at 0 year of neighboring age. At 3 years of neighboring age, however, the rates of the two become roughly equivalent. The relation of D and E observed by post-eruptive tooth age in the previous paper exhibited an opposite situation. By either method of counting it is impossible to observe the situation of two teeth that have different eruption times like D-E under the same condition. It was presumed, however, that if they were placed under the same condition the proximal surfaces between D and E would show the same pattern.Table 5 shows the comparison of Mx between the Contact group and the Space group. It may be of use in the assessment of the effectiveness of floss silk in the prevention of caries.