Occlusion in the primary dentition in 3-year-old children.

The material for the present study comprises plaster models of 310 Copenhagen children, impressions for which were taken during the month each child attained the age of 3 years. On the basis of fixed criteria a description is given of individual symptoms of occlusion. Using the primary canines as the guide to occlusion it was found that the same occlusion at both sides occurs in 79.7% of the overall total, the remaining 20.3% having different occlusion at each side. Approximately one-half recorded neutral occlusion at both sides, and one-third had distal occlusion at both sides. The termination pattern of the dental arches in centric occlusion were normal or straight in 68.0% and bilateral distal in 14.8%. In 82 subjects or 27% of the degree of overlapping was greater than or equal to half the height of the mandibular central incisors. The number of cross-bites constituted 11.6% of all subjects. Assessment of spacing was undertaken exclusively on the basis of whether or not a space existed. About 3.5% of all subjects had close contact between all teeth in the maxilla or crowding, and about 24% had spacing between all teeth in the maxilla. In the mandible about 5% had close contact between the teeth and only 15% had spacing between all teeth in the mandible.