We performed a three-dimensional study of tooth position and anteroposterior and lateral occlusal curvature with linked cusp tips, to investigate anterior cross bite in the deciduous dentition.
Dental casts of the maxilla and the mandible were obtained from 36 subjects (16 males,20 females) showing anterior cross bite in the deciduous dentition. A three-dimensional measurement device (Xyzax) was used to reproduce the spatial relationships of the incisal edges, buccal cusp tips and lingual cusp tips to the standard plane, and then the continuous curves of the incisal edges and either the buccal cusp tips or lingual cusp tips were reproduced. The lines of the buccal and lingual cusp tips were also reproduced.
On the continuous curve of the incisal edges and buccal cusp tips, the upper peak in the maxilla was found on the lateral incisors in both males and females whereas the lower one in the maxilla was found on the first molars in males and on the cuspids in females. In the mandible, the upper one was found on the cuspids and the lower one was found on the distal cusp tips of the first molars in both males and females.
On the continuous curve of the incisal edges and lingual cusp tips, in the maxilla, the upper peak was found on the lateral incisors whereas the lower one was found on the mesial cusp tips of the second molars in both males and females. In the mondible, the upper peak was found on the cuspids and the lower one was found on the distal cusp tips of the first molars in both males and females.
Regarding the angles subtended by the lines of the buccal and lingual cusp tips and the standard plane, the value for the second molars was larger than that for the first molars in the maxilla but in the mandible the value for the first molars was larger than that for the second molars in both males and females.
The degree of curvature of the continuous curve of the incisal edges and buccal cusp tips tended to be greater in subjects with a deep overbite than in those without it.