Abstract
One of the important purposes of orthodontic treatment for the cleft lip and palate patients following cheiloplasty and palatoplasty is to expand the upper dental arch and improve the cross-bite. It is difficult in some cases, however, to achieve good results as we expected. In this study, the amount of cross-bite before and after expansion was measured on the dental casts using special gauges to evaluate limitation of the improvement of the cross-bite. The materials consisted of plaster models obtained from 37 unilateral and 18 bilateral cleft lip and palate. patients whose orthodontic treatment had started at the ages from 6 to 11 at the Orthodontic Departmen t, Osaka University Dental. School Hospital.
As the control, the longitudinal p laster models obtained from 20 non-cleft subjects were used. The age of the control group was matched with the cleft lip and palate group. The amount of cross-bite was measured at the areas of the central incisors, the cuspids and the first molars
The following results were obtained
1) The condition of cross-bite before expansion of upper dental arch: In UCLP group, the most severe cross-bite was found at the incisor area followed by the cuspid area and the first molar area. The amount of cross-bite on the cleft side was larger than the non-cleft side at each area. In BCLP group, almost the same amount of cross-bite was observed at each area as what was observed on the cleft side of UCLP group.
2) The condition of cross-bite after expansion of upper dental arch: In both of UCLP and BCLP groups, satisfactory improvement of cross-bite was achieved at the first molar area. However, in the areas of the central incisors and the cuspids, the cross-bite still remained in most cases in spite of the expansion as much as possible.
3) The change of the upper dental arch following expansion:
On the average, the change on the cleft side in UCLP group was larger than on the non-cleft side and also larger at the areas of the central incisors and the cusphds than the first molar area. At each area the larger change was observed in UCLP group than in BCLP group. In the individual cases, however, a lot of variations were found in the manner of expansion of the upper dental arch. The appliance for unilateral expansion is required to achieve expansion more effectively.
