Changes in tooth size—arch length relationships from the deciduous to the permanent dentition: A longitudinal study

Abstract

The purpose of this investigation is to determine the changes in the maxillary and mandibular tooth size-arch length relationship (TSALD) after the complete eruption of the deciduous dentition (x̄ age = 4.0 years) to the time of eruption of the second molars (x̄ age = 13.3 years). In addition, an attempt was made to determine whether TSALD in the permanent dentition can be predicted in the deciduous dentition. Records on 35 male and 27 female subjects were evaluated. Each subject had a clinically acceptable occlusion—that is, a normal molar and canine relationship, at the time of eruption of the deciduous and permanent teeth. In addition, each subject had a complete set of data at the two stages of dental development. These selection criteria limited the number of subjects in this investigation to 62. The mesiodistal diameter of all deciduous teeth and their permanent successors, as well as various dental arch width and length parameters, were measured in the deciduous and permanent dentitions. A total of 68 parameters were measured or calculated. Student t tests were used to determine whether significant differences were present between the right and left sides for both male and female subjects. Correlation coefficients r were performed between the deciduous and the corresponding permanent teeth and also for the arch length parameters, as well as TSALD in the two dentitions. Significance was predetermined at the 0.05 level of confidence. Stepwise regression analysis (R 2) was used to determine which of the variables in the deciduous dentition could be included in a regression model to determine associations between maxillary and mandibular TSALD in the permanent dentition. The results of the correlation coefficients ( r) indicate that there are a number of significant correlations between the various variables in the deciduous and the permanent dentitions, but most of these correlations were relatively low (< 0.7), with the exception of those for the incisors, in the female subjects. The Multiple Regression Analysis did not significantly improve the predictive abilities. Discriminant Analysis indicated that the predictive accuracy, i.e., the percentage of cases correctly classified by the prediction equations were, in general, relatively low. In conclusion, the changes in the alignment of the teeth were primarily the result of a decrease in the available arch length in both the maxillary and mandibular arches. The correlations between the various deciduous and permanent parameters are of such a magnitude that does not allow an accurate prediction of the TSALD in the permanent dentition from the available dental measurements in the deciduous dentition. The clinical implications of the findings were discussed. (A M J O RTHOD D ENTOFAC O RTHOP 1995;108:607-13.)