Introduction: The aims of this study were to elucidate the mechanism of the dental crowding and to predict dental crowding of permanent dentition from mixed dentition using longitudinal dental casts (from first grade to sixth grade in primary school).
Methods: Subjects were mandibular dental casts of 50 children. Dental arch width, dental arch length, bucco-lingual inclination of first molar, and amount of dental crowding of six grade (permanent dentition) were measured. Subjects were classified into normal group(ALD>-2.5mm) and crowding group(ALD≦-2.5mm). The multiple regression analysis was performed to predict ALD at permanent dentition.
Results: After second grade, dental arch width and annual changes of first molar inclination in crowding group were significantly smaller than those in normal group. There is no significant difference in tooth size and def rate between normal group and crowding group. As a result of multiple regression analysis, using fourth grade measurement value and quantity of annual change as explanatory variables showed 0.80 for multiple R.
Crowding=-0.44(annual change of first molar inclination)-0.49(arch width of first molar)+1.31(annual change of first molar arch width)+24.78
Conclusion: Crowding group showed narrow dental arch width and first molar inclined lingually. In the case of normal tooth size and caries free dentition, crowding of permanent dentition could be predicted from mixed dentition.