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A sample of 4724 children (2353 girls and 2371 boys) (5-17 years old) were grouped not only by chronological age but also by stage of dental development (deciduous, early mixed, late mixed, and permanent dentition). The registrations included functional occlusion (anterior and lateral sliding, interferences), dental wear, mandibular mobility (maximal opening, deflection), and temporomandibular joint and muscular pain recorded by palpation. Headache was the only symptom of temporomandibular dysfunction (TMD) reported by the children. The results showed that one or more clinical signs were recorded in 25% of the subjects, most of them being mild in character. The prevalences increased during the developmental stages. Girls were in general more affected than boys. Significant associations were found between different signs, and TMD was associated with posterior crossbite, anterior open bite, Angle Class III malocclusion, and extreme maxillary overjet.

Infraocclusion of deciduous molars that also lack a permanent successor is found to progress more than where a successor is present, while exfoliation is severely retarded. The aplasia is the most important factor in treatment planning and timing.

The activity of the temporal and masseter muscles with the mandible in postural position and during chewing, maximal bite in the intercuspal position, and swallowing were recorded electromyographically in nineteen children with laterally forced bite. Of the children, aged 8-12 years, sixteen had unilateral crossbite. In all of the individuals there was lateral deviation between the retruded contact position and the intercuspal position. The magnitude of the lateral deviation was measured with a modified gnathothesiometer. The muscle activity was recorded bilaterally from the temporal muscle and from the masseter muscle. In the postural position asymmetric activity was found in the temporal muscle suggesting that the mandible in postural position was still displaced to the side of forced bite. During chewing the activity was asymmetric both in the anterior and the posterior temporal portions. This asymmetric muscle activity was interpreted as an adaptation to avoid cuspal interferences. Also in maximal bite the muscle activity was asymmetric, while the activity during swallowing was affected less than in the other functions. The swallowing activity was, however, less in children with a forced bite than in children with normal occlusion.

An experimental study in dogs, in which 15 teeth were bodily moved and 9 teeth were tipped with the same amount of horizontal force. Less resorption was found with tipping, and less was found on the mesial root surfaces moved into the extraction sites than on the furcation side of the distal roots.