[Changes of the arch form and occlusion of the deciduous open bite cases: a longitudinal study].

The purpose of this study was to determine the characteristics and longitudinal changes of the arch morphology and occulusion of the deciduous open bite cases. The materials used in this study were the serial plaster casts of 40 Japanese children with deciduous open bite, and they were measured with the three dimentional system. The following results were obtained: 1. The form of dental arch with open bite in the early primary dentition changed remarkably in the maxilla but little in the mandible. In children with open bite, the maxillary intercanine distance was narrower, the maxillary arch length was longer, the palatal height of the front area was higher, but the back one was lower, and the upper central primary incisors were located more forward and upward higher than in children without open bite. 2. In the late primary dentition, the dental arch shape in the spontaneous closure group showed little difference from the control group. However the deciduous upper central incisors of the spontaneous closure group were very remarkably inclined to the palatal side, and the vertical over-jet was larger than that in the control group. The larger the horizontal over-jets were in the early deciduous dentition, the larger the vertical over-jet changed in the late deciduous dentition. 3. In the spontaneous closure group, the point of the dental arch showed a regular changing aspect, in which place marked variation was recognized in the early deciduous dentition as compared with the control group. Because of spontaneous closure, the dental arch shape approached the one of control group rapidly. 4. The result of multivariate analysis indicate that not only discontinuance of thumb-sucking but also many variables of the dental arch shape and occlusal condition may induce spontaneous closure of the open bite within the deciduous dentition term.