Physiological Tooth Migration and its Significance for the Development of Occlusion

A NY attempt to develop preventative methods in the field of orthodontics must be based on adequate knowledge of normal growth and development of the dentitions and the many modifying factors. A review of the literature reveals little authentic information on which the present-day concept of the development of occlusion is based. Delabarre, in 1819, described for the first time the spacing of anterior deciduous teeth between the ages of 4 and 6 years and suggested that the purpose was to make allowance for the permanent ones.15 This concept prevails among most writers of recent textbooks (Dewey-Anderson" 6 Korkhaus,14 MeCoy,20 Salzmann,26 Schour and Massler,'27 and Strang.35 Zsigmondy3' in 1890, was the first to measure the lengths of the dental arches of three series of models of the same individual between 6 and 17 years of age. After Angle39 published his Malocclusion of the Teeth in 1907, the main interest turned from genetics to the systematics of malocclusion. Thus, Angle's theory of the fixed position of the upper first molars became an established law in orthodontics. In 1910, Zielinsky37 concluded from measurements of four skulls and some models of various individuals that, between the ages of 4 and 6 years, the upper anterior deciduous teeth move forward and laterally. This spreading of the upper dental arch would cause a spacing of the deciduous anteriors and simultaneously a forward migration of the mandibular deciduous teeth into the enlarged maxillary arch. This concept is known as the so-called "physiological mesial shift" of the mandibular teeth." 14, 20, 26, 35 In 1922, Franke,7 from numerous skull measurements, calculated a shortening of 3.7 mm. in the lower dental arch following the shedding of the deciduous teeth. Simon,34 in 1924, presented his biometric law of the "orbit-cuspid relationship" establishing the possibility of positional changes of the upper permanent molars. Kantorowicz13 was the first to emphasize the necessity for a genetic approach to the classification of dentofacial and ocelusal anomalies on the basis of a large number of serial models of development. In 1927 Schwarz28 reported a comprehensive anatomical study of the problem. He accounted for ocelusal adjustment by means of tooth morphology. Friel's8 de-