Tooth to denture base discrepancy, one of the major etiologic factors of malocclusion, is considered to have its origin in human evolution. The objective of this study is, therefore, to survey the general trend of the transitional change of frequencies of malocclusion and discrepancy through the history of man.The materials used were 122 skulls from Jomon, Kofun, Medieval, and Yedo eras, preserved in the University Museum, The University of Tokyo. On these materials, the occlusal patterns (malocclusions) and their pathogenetic factors were investigated. The control data for modern Japanese were cited from previous papers of the present authors.Frequencies of normal occlusion were 80% in Jomon period, but gradually decreased to 23.8% in modern age, while those of discrepancy showed a rise from 8.9% up to 63.1%. These remarkable changes seem to support the authors' opinion that the most substantial progress of discrepancy has occurred during these two thousand years, giving a marked influence to the distribution of malocclusions.
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Hanihara et al. (1981) studied this question.