Abstract
With the method to observe the caries incidence during the limited period by “one tooth as unit”, they found out extremely close timely and quantitative relation between an average sugar consumption of a Japanese during the year and the caries incidence during the year on first molar after the dentition of them. The author carried out an epidemiological study on both upper central and lateral incisors as a different crown type tooth from the first molars, by Takeuchi, Takahashi and Koike.
Namely, employing as material, the dental examination records of 10, 288 primary school children in Tokyo and Kyoto range over pre-war, mid-war and post-war time and six years continued dental examination records on 8, 393 students of junior and senior high school in Tokyo.
He made an epidemiological study on relation between an average sugar consumption of a Japanese during a year and a caries incidence during a year pursue it after the dentition on the Cohorts which are divided by their dentition by “one tooth as unit” about upper central and lateral incisors and obtained a following results.
1. On upper central and lateral incisors period of the average sugar consumption of a Japanese during a year shows 15kg, when the “odont-age” -amount of years after the dentition-shows 5-9 years caries incidence during a year is 3-5 %, but when the average sugar consumption are reduced from 10 kg to 0.2kg caries incidence during a year reduce with timely agreement taking 2-3 years lateness comparatively closely and when the average sugar consumption increases caries incidence increases too.
2. Coefficients of correlation between the caries incidence and the sugar consumption on the year of new caries incidence-year before of new caries incidence on upper central and lateral incisors are about 0.5 and the coefficients of correlation between caries incidence and the sugar consumption on 2-3 years before the new caries incidence shows higher result than it on the year of new caries incidence.
That ratio to the cumulative sugar consumption during the year of tooth formation is low.
3. The pattern of the caries incidence per year in pre-war period while the sugar consumption shows a constant quantity to compare with the pattern of the first molars, on upper central and lateral incisors, the period which has a biggest incidence after the dentition is delayed 3-4 years to the first molars'.
4. Increasement of the rate of an incidence per year of 1 year 3 years before the new caries incidence on upper central and lateral incisor in 5-9 odont-age and the increasement of the sugar consumption in a year of new caries incidence show a almost streight line on semi-log graph, and the proportion of the inclination shows almost parallel with the first molars'.
5. According to the above mentioned result he recognized, the relation between average sugar consumption of a Japanese during a year and the caries incidence on upper central and lateral incisors are close after the dentition than the period of tooth formation and also he presumed the reason of the fact that a relation to the sugar consumption during a year is not close timely like a case of the first molar.
