Longitudinal study of occlusion in the primary dentition in 3- and 7-year-old children.

The material for the study comprises plaster models of 269 Copenhagen children, the impressions for which were taken during the month each child attained the ages of 3 and 7 years. A comparison was made of occlusion in the single child in the period. The study illustrates clearly that the same given percentage in two age groups is by no means a guarantee that there have been no changes. The canine relationships in particular are unstable during the period of study. The only stable occlusion is distal occlusion in the primary dentition. This occlusion is invariably maintained and is always transferred unchanged to the permanent dentition.