Facial development and tooth eruption. An implant study at the age of puberty.

Abstract By means of the implant method, the eruption paths of the teeth have been analyzed in relation to facial development and growth of the jaws; growth changes were followed in longitudinal series of profile radiographs of twenty-one subjects. To ensure uniform conditions with respect to physical maturity, the analysis was confined to the 6-year period around puberty. Various types of malocclusion were represented. No orthodontic treatment was performed during the observation period. The series is presented in the form of growth tracings, photographs of casts and faces, with data on growth changes for each subject, so that the reader is afforded the opportunity of making his own interpretation. A general feature of the facial development was a more or less marked forward rotation of the face, including the two jaws, but greater for the mandible. There was a strong association between the facial rotation and the condylar growth. At the lower border of the mandible about one half of the rotation was masked by a compensatory remodeling in this area. At the posterior border of the ramus about four fifths of the mandibular rotation was masked by compensatory remodeling. The rotation of the maxilla was likewise masked by remodeling of the nasal floor, which remained almost unchanged in inclination. While the rotation of the mandible during growth can be judged clinically from internal structures, there is no similar orientation method for the maxilla; the path and the degree of eruption of the upper teeth therefore cannot be analyzed without the use of implants. The rotation of the face necessitates compensatory adaptation of the paths of eruption of the teeth. When there is full compensatory occlusal development, the lower incisors retain their inclination in the face practically undisturbed, irrespective of the rotation of the jaw, because of a forward tipping on the jaw base. The posterior teeth in the lower jaw, too, are involved in this compensatory occlusal development and are likewise tipped forward. The lower dental arch then shifts forward on the jaw base without undergoing any appreciable change in shape. The intermolar inclination remains comparatively constant as the lateral teeth in both jaws follow the rotation of the face. What clinically has been regarded as an eruption of the upper molars appeared to be a combination of active eruption of the teeth in the jawbone and bodily rotation of the maxilla. This is a new aspect of occlusal development which may have clinical implications. A general conclusion that may be drawn from the results is that malocclusions are to a greater extent due to incomplete compensatory guidance of eruption than to dysplastic deformation of the dental arches. Prophylactic and interceptive measures should therefore be focused on the factors potentially responsible for impairing the compensatory mechanism. In the planning of orthodontic treatment the therapy should be designed to take into account the action of such forces on the development of the occlusion.