Abstract: The materials investigated were 91 maxilhary first permanent molars of Southern Chinese.
The method of area measurement of structures of the teeth on longitudinal section is applied. The crown-chamber index was calculated according to the following formula:
Crown-chamber index = [ (area of enamel + area of pulp chamber) / (area of dentine of erown) ]×100
The regression formula to estimate age is:
Y=72. 32-0: 442X.
(X=crown-chamber index)

Key words: Area measurement of structures; Crown-chamber index; Regression; Southern Chinese