In this research we used 180 noncarious teeth, 15 from each kind, in which we cut the anatomic crown. After that we weighted the roots, each group separately, before and after the root canal obturation with the technique of lateral condensation of gutta percha and Grossman's sealer. The difference of the two weights represent the overload of the tooth after obturation. Then using mathematical rules we configured out the mean volume of the root canal of each group and the mean value of the diameter of the orifice of the canal of each group of teeth.