Abstract The dentition is a fundamental process in life. Then the almost‐one parameter hypothesis suggests us that the individual difference would be represented by one parameter. In fact, the logarithmically transformed chronological ages Y α i at the eruption of deciduous teeth D α are represented by a linear equation of its mean Y α .(4), where two coefficients a i , and b i are highly negatively correlated. It implies the existence of a quasi‐fixed point close to this line. See Fig. 1 and Fig. 2, where this point is denoted by a cross. This point is utilized to forecast the age at the subsequent eruption.