The Patterning Cascade Model and Expression of the Carabelli Feature in Humans: Differences Between First and Second Molars and Correlation with Other Dental Traits
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Date
2011-06
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The Ohio State University
Abstract
The Patterning Cascade Model of tooth development suggests that cusp formation follows a sequential developmental pattern. Enamel knots, specialized cells in a developing tooth from which cusps initiate, act as signaling centers in this developmental cascade. To form, an enamel knot must escape inhibition fields produced by other enamel knots. The Model predicts that the number and size of cusps will vary as a function of intercusp spacing relative to tooth size. The present research builds on work by Hunter et al. (2010) on the Carabelli feature, a common human dental character. These researchers found that the model predicted Carabelli feature expression in first molars. The focus of the present research is to determine if differences in the expression of Carabelli feature along the molar row can be predicted on the basis of the Model as well. These differences were assessed through a comparison of relative intercusp distance between first and second molars. Tooth sizes and intercusp distances were measured three times from dental casts of 380 individuals using a Hirox digital microscope. The results of this study show that the degree to which the Carabelli feature is expressed on first versus second molars is consistent with the Model’s predictions. Other dental features were found to covary with the Carabelli feature. The results of this study suggest that dental traits are not independent of each other and instead develop in a dependent manner. This is important to consider because the degree to which dental traits covary must be taken into account when assessing evolutionary relationships based on these traits.
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Keywords
Carabelli, Patterning Cascade Model, Hypocone, Carabelli cusp, Second Molars