Abstract
The Fourier analysis was used to determine and characterize the average forms of coronal and basal arches of deciduous anterior crossbite and to compare them with those of normal occlusion. Moreover, the morphological changes before and after treatment in the anterior crossbite treated orthodontically were studied. The materials consisted of 50 girls' stone casts of nomal deciduous dentition and 20 girls' stone casts of anterior crossbite. Their average age was 3-3/4years. The following conclusions were obtained.
(1) The averge form of the maxillary dental arch of the anterior crossbite was characterized by deviation from the normal curve in the second deciduous molar, the distal region of the deciduous lateral incisors and the central portion of the deciduous central incisors. In the mandible, deviation was noted in the second deciduous molar, the central region of the deciduous central and lateral incisors and between the deciduous cuspid and the first deciduous molar.
(2) The maxillary and mandibular bpsal arches showed deviation from the normal curve in the second deciduous molar and the central region of the deciduous central incisors; in paticular mandible deviation was also observed in the distal portion of the deciduous cuspids.
(3) Definitive differences were observed in the maxillary dental arch, maxillary basal arch and mandibular basal arch between the normal occlusion and the anterior crossbite.
(4) After orthodontic treatment, the forms of the maxillary dental and basal arches changed and approached those of the normal occlusion.
