The mean times of eruption for the canines, premolars and second molars for Danish school children of 1965 were compared with those given by Degerbøl (1931) for Copenhagen school children of 1913. The average of the differences between the two samples in the eruption times of the individual teeth was small. A differentiated secular trend was observed for the various types of teeth. In both sexes, the 1965-sample displayed an earlier eruption of M2 and C in both jaws and of the lower P1. The 1913-sample showed an earlier eruption of P2 in both jaws and of the upper P1. The interval between the first and last erupting tooth was shorter in the 1965 sample. The mean eruption sequences of the two samples differed, and the interval between the eruption of P2 and M2 was markedly reduced in the 1965-sample, expecially in the lower jaw. All the eruption times were more variable in the 1913-sample except for the M2 in the boys. In both samples all the teeth erupted significantly earlier in the girls. The sex difference in eruption times averaged approx. 6 months. There was no appreciable sex difference in the variability of the eruption times. It is argued that since the general physical development was at least 1 year accelerated in the 1965-sample while the dental development as a whole was practically constant in the two samples, the differentiated secular trend in eruption may be associated with a different relation between the timing of dental and general physical development in the older and contemporary sample. © 1969.
