[Trend of aging on the number of teeth investigated through a survey of dental health representation in a simple equation by using a kinetic method and its application].
A survey of dental health was conducted on 6,933 residents (aged 61.8 +/- 11.1) in 4 villages Nara Prefectural Uchiyoshino Health Center administers. Examinees were divided into 7 ages groups. The mean value of present teeth at each age group was calculated. Age dependency of number of teeth was investigated with a kinetic model based on the following premise. 1. Changes between age groups can be treated as a time series occurrence. 2. Number of missing teeth can be estimated as 29 - that of present teeth. Results show that the rate of decrease of the number of present teeth is of a first order in itself and the number of missing teeth. It can be mathematically expressed as follows: -dX/dt = k.X.(29 - X).......eq. (1). in which X = number of present teeth, 29 - x = number of missing teeth k = rate constant, t = time. From this simple relationship the following are suggested 1. Tooth loss is caused by the interaction of present teeth and sites where teeth are lost. 2. Integration of eq. (1) yields ln¿(29 - X)/X¿ = 29.k.t + a.......eq. (2). in which 0 < X < 29, t = time from the youngest age group (20-29), a = constant. It appears that, from eq. (2), the dental health of a community is determined by two coefficients, 29.k and a. 3. Helping a person realize his present and future dental state and to motivate action for prevention of tooth loss by showing him his rate of decrease, "tooth age" and the predicted number of teeth a certain years later calculated from eq. (1) and eq. (2), can be of great value. 4. Eq. (2) is transformed to X = 29/¿exp(29.k.t + a) + 1¿, which represents the reverse S-shaped curve of the age dependency of the number of teeth. 5. Applying this method to cohort analysis will enable forecast of the trend of the number of teeth.
Takeda
K
K
Uchiyoshino Public Health Center, Nara Prefecture.
Horiuchi
K
K
Yagyu
Y
Y
Yamada
M
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D003753:Dental Health Surveys; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D016388:Tooth Loss