Abstract
Utilizing data obtained in a dental disease public survey conducted by the Ministry of Welfare in 1957, this writer studied how the number of existing teeth changes in each sex and age group, and succeeded in estimating the number of existing teeth for each age group by the following equation, where X represents the age and Y, the number of existing teeth:
1) In males, Y=26.96+0.16X-0.006X2.
At 17, 28 teeth; at 67, 13 teeth.
2) In females, Y=26.90+0.18X-0.007X2.
At 17, 28 teeth; at 67, 8 teeth.
3) In general: Y=25.87+0.21X-0.007X2.
At 17, 28 teeth; at 67, 10 teeth.
These tendency curves all proved highly significant through examination by the dispersion analysis method and showed good agreement with the examination results. The coefficients of interrelation between the age groups and the tooth number groups where as follows:
A) Male: r=-0.96±0.02
B) Female: r=-0.97±0.02
C) General: r=-0.96±0.02
Through examination it was found that P=0.001 in all these cases, showing that these values are significant. No significant difference was noted between males and females.
