A step function model using tooth counts to assess the developmental timing of the dentition.

Step functions representing median attainment ages of successive counts on numbers of permanent teeth present in the mouth were obtained separately for 12 early-emerging teeth (I1, I2 and M1) and for 16 late-emerging teeth (C, Pm1, Pm2, and M2). Displacement of each step function to best fit of individual tooth counts defined the variation in dental maturation for early teeth and for late teeth. Moreover, differences in the displacements of the two-step functions defined individual variations in the duration of the emergence process.