Study on Epidemiological Pattern of Caries Attack in Deciduous Teeth.

Abstract

Though Takeuchi and his group have clarified epidemiological phenomena of caries attack in parmanent teeth, no study of this sort has been done in deciduous teeth. Therefore, this study was made to obtain basic epidemiological patterns of caries attack in the deciduous teeth for each type of tooth when the annual sugar consumption per head (represented as p) was constant.
For this purpose, the central part of Kameoka City near Kyoto (Fig, 1), was chosen as the place of investigation. The standard of living in this place was about the average of Japan (Table 1) and the flouride content in the drinking water was insignificant in relation to caries attack (Table 6) . Considering all of the infants aged 0, 1 and 2 years in 1965 in this area as population, a semi-annual oral examination for longitudinal study was carried out in the same individuals for 3.5 years (Table 2) . During this period (p) was 19-22 kg. Examination was performed by a dentist (the author) with an explorer and a dental mirror, considering as carious the pits and fissures that were clearly sticky or worse and the surfaces that were rough or had worse changes.
Only the teeth observed from their post-eruptive tooth age 0 were calculated at every half-year, putting the teeth of the same denomination of both sexes and left and right sides together, and separating those of different types, using a tooth or a surface as the unit of caries attack (Table 3) . Three kinds of indexes were calculated by the following method
Caries incidence rate during post-eruptive tooth age x (Mx) = Number of teeth newly attacked by caries during post-eruptive tooth age (x-0.5 yr. ) to x-yr. / Number of sound teeth at the post-eruptive tooth age (x-0.5 yr. ) ×100 The number of teeth newly attacked by caries during the post-eruptive tooth age x (per six monthes) per initial 1, 000 teeth (Cx) was calculated with Mx as follows: Tooth age Number of sound teeth (Sx) Cx 0 S₀ = 1, 000 S₀×1O M₀=C₀ 0.5 (S₀-C₀) = S_0.5 S_0.5×1O M_0.5 = C_0.51.0 (S_0.5-C_0.5) = S_1.0 S_1.0×1O M_1.0=C_1.0The cumulative number of carious teeth up to the post-eruptive tooth age x-year (per six monthes) per initial 1, 000 teeth (ΣCx) is the accumulation of Cx. The same methods were used in the calculations of the tooth surface. Furthemore, the e^-kx line was drawn by the method shown in Fig. 2, and from the polygonal lines of Cx and ΣCx, their trend lines were plotted.
The three indexes of caries (Mx, Cx and ΣCx) were shown in Table 4. In graphs the polygonal lines of Mx are shown in Figs. 3 and 4. The polygonal line of Cx is shown in Fig. 5 and the polygonal line of Cx in Figs. 7 and 8. The trend lines of Cx and ΣCx, and the e^-kx line are as shown in Fig. 9. The angle between the e^-kx line and the 1-line and the post-eruptive tooth age at which Cx trend line reached its summit are shown in Table 9.
It was conceivable that Fig. 9 shows a typical pattern of caries attack on the deciduous teeth in Japanese infants when (p) is around 20 kg. It was noticed that the Cx trend line of this figure coincides with integrals of exponential probability and that the e^-kx line is a straight line. From these facts it was deduced that at least in the case of deciduous teeth and when (p) is constant, caries occurs as a phenomenon in which the resistance of the tooth makes the normal distribution as a process in the first stage, then as the second stage, an initial carious change appears in accordance with the chance of caries which is constant (Fig. 10).
Patterns of proximal surface caries were also discussed (Figs. 6, 11, 12).