Cluster analysis of tooth size in subjects with normal occlusion.

Introduction: Tooth-size studies are important in orthodontics. Our aim in this study was to establish normative data on tooth size with a clustering method.

Methods: Dental casts of 307 subjects with normal occlusion were examined. In these subjects, the tooth-size data sets in the maxilla and the mandible were clustered for men and women by using multivariate normal mixture models. This analysis clustered the data sets into groups of observations that were cohesive and separate from the other groups. The parameters were estimated with expectation-maximization procedures, and the number of clusters was selected via the Bayesian information criterion.

Results: Seven heterogeneous clusters in men and 4 clusters in women were identified. This study indicated that, in normal occlusion, tooth sizes are variable. These heterogeneities in the normal occlusion group seem to have contributed to the variability found in normative data.

Conclusions: The method used in this study seems to provide a more substantive design for artificial teeth and add an additional dimension in the process of diagnosis of patients. Further applications seem possible in dental anthropometry by simultaneously dealing with the full dentition as a data set.