[Changes of the chewing movements following the correction of anterior reversed occlusion in children].

The purpose of this study was to investigate the functional changes following the orthodontic treatment of anterior reversed occlusion in children. Samples consist of 94 children with anterior reversed occlusion as the experimental group and 34 children with normal incisor occlusion as the control group. Experimental samples were classified into 3 groups according to the erupting stages of incisors. Among them, a group of the permanent incisor dentition was divided into 2 groups, one was a "Shift group" showing functional mandibular movement from the centric relation to intercuspal position and the other was a "non-shift group" showing no such functional movement. In the experimental group, 28 patients showed the correction of anterior reversed occlusion orthodontically. Mandibular movements were recorded during gum chewing on all subjects by using Sirognatho Analysing System II. Mandibular movement was examined as to the cycle time and the chewing movement on the horizontal plane. The results were as follows: 1. The chewing cycle was irregular in samples of reversed occlusion. 2. Samples of reversed occlusion with deciduous incisors and of normal occlusion were equivalent in the cycle time. 3. The chewing cycle was more longer in samples of reversed occlusion with maxillary deciduous and mandibular permanent incisors than those of normal occlusion. 4. The chewing cycle was longer in the Shift group than in the normal group. But it was not longer in the Non-shift group than in the normal group. 5. The chewing movement of the Shift group showed type-1, 2, 3 rather than type 4. But the non-shift group showed type-4 more than type-1, 2, 3. 6. The chewing cycle became more regularized after the correction of anterior reversed occlusion. 7. The chewing cycle was shortened in the Shift group after the correction of anterior reversed occlusion. 8. The chewing movement of type-1 and type-4 were decreased after the correction of anterior reversed occlusion. In conclusion, the correction of anterior reversed occlusion by orthodontic method provides improvements of not only the morphological incisor occlusion but also the functional mandibular movements.