3d morphometric analysis of human primary second molar crowns and its implications on interceptive orthodontics

The second primary molar represents an anchorage element in interceptive orthodontics. The present study aims to analyze the 3D morphology of primary second molars in order to provide reference data and implications about the development of orthodontic bands for second primary molars. Digital models of dental arches from 150 subjects in primary or mixed dentition were analyzed. Six dimensional variables were digitally measured for each second primary molar, and the mean and standard error of the mean (SEM) were calculated and compared applying Student t-test statistical analysis. The mean value results show statistically significant dimensional differences between the upper and lower teeth, (mostly p < 0.0001), except for the variable h1, while only the variable h1 showed significant differences between the antimetric teeth (left and right). The dimensional variations between the right and left molars were considerably minor compared to those found by comparing the upper and lower arches. A significantly higher dimension of the lower molars and a more rectangular shape were observed.