Correlations between deciduous and permanent tooth morphology in a European American sample

The expression of dental morphological characteristics is partially genetically controlled, and is assumed to be similar in deciduous and permanent dentitions. However, there are few published data comparing normal morphological variation between the two dentitions in the same individual. For the current study, data were collected from European Americans (N = 54) whose teeth were cast both as children and adults. We observed 19 trait expressions in deciduous and permanent dentitions. Deciduous traits were scored based on Hanihara's and Sciulli's descriptions, while permanent teeth were scored using the ASU dental anthropology system. The two dentitions' scores were compared using Goodman-Kruskal's Gamma (gamma) in the original, commonly used systems as well as in a new, shared scale to which the scores were converted. Observations were also dichotomized in both formats and compared using tetrachoric correlation. We expected high correlations between the two dentitions and for both statistics to yield similar results. For the original scores, gamma correlations vary from -1.0 to 0.68; tetrachoric correlations vary from 0.04 to 0.67. For the shared scale scores, gamma correlations range from -1.0 to 1.0 and tetrachoric correlations range between -0.47 and 0.8. Several traits showed no correlation in either test. Overall, categorical data analysis returned more positive moderate to high correlations than tetrachoric correlation analysis, and shared scale tests resulted in more correlations than did tests of data in the original scoring systems. These results reflect differences in commonly used scoring systems, variation in rarely occurring traits, different strengths of trait expression, and complex genetic/environmental interactions.