Tooth to denture base discrepancy in human evolution

Abstract

Tooth to denture base discrepancy is a concept which has been developed by orthodontists as their diagnostic measure for the decision of permanent tooth extraction for orthodontic treatment. It is now coming to be considered as one of the major etiologic factors, not only in malocclusion, but in dental caries, periodontal disease, pericoronitis, tooth impaction, dentigerous cyst, and so on.In the present paper, these instances were shown (Figures 1-3), and the nature and origin of this unfavorable phenomenon were discussed from the stand point of human evolution and civilization.The author's conclusive opinion may be summarized as follows: Under the close effect of civilization, especially of the eating behavior, diminution of the facial bones and the tooth has consistently taken place through the course of human evolution. However, the rate of reduction was higher in bones which is more labile to the circumferential functional stimuli, while the tooth has been more stable because the tooth crown does not have any remodeling process after the completion of its formation. Thus the disharmonious diminution of these two components of occlusion, being accompanied with the acceleration through the selection by favorable facial esthetics directed to the orthognathism, has resulted in the discrepancy.Considering the rather rapid increase of malocclusion, dental caries, and other related disorders in the present era, even collapse of human occlusion might be expected in relatively near future, if a catastrophic rush occured in further development of the discrepancy.The present study on the discrepancy problem has brought to the author the poignant realization that the interdisciplinal communication between anthropology and dentistry is really worthwhile, and even requisite for further advance in both of these fields.