[Factors that affect alignment of upper permanent lateral incisors in early mixed dentition]

The purpose of the present study was to find the factors that affect the alignment of the upper permanent lateral incisors in early mixed dentition. The materials, consisting of dental casts and lateral cephalograms which were taken from 30 children (15 males and 15 females) who had normal occlusion in deciduous dentition and normal permanent central incisor relationship, were divided into three groups, according to the bilateral symmetry alignment of the upper permanent lateral incisors (Group A: Normal alignment, Group B: Linguoversion, Group C: Mesiolinguotorsiversion). The principal component analysis was carried out to clarify the characteristics among the multi-variates, which are upper incisor shape, dental arch form, craniofacial morphology and amount of dento-craniofacial development, in Groups A, B and C. The results obtained were as follows: Group A shows a tendency to be harmonious in upper permanent incisor shape, dental arch form, craniofacial morphology and dento-craniofacial development. Group B shows a tendency to have a larger labio-lingual width of the upper permanent incisors, less anterior arch length development and less forward movement of the upper permanent lateral incisor in the maxilla before eruption. Group C shows a tendency to have a larger mesio-distal width of the upper permanent incisors, less anterior arch width development, longer distance between the upper permanent lateral incisor edge and the nasal floor and more forward and descent movement of the upper permanent lateral incisor in the maxilla before eruption.