PHYSIOLOGICAL TOOTH MIGRATION AND ITS SIGNIFICANCE FOR THE DEVELOPMENT OF OCCLUSION

IV. THE BIOGENESIS OF OVERBITE

¹ Division of Dental Medicine, College of Dentistry, and the George Willlams Hooper Foundation for Medical Research, University of California, San Francisco, Calif.

In a survey of 52 cases the development of overbite was studied. The following summarizes the findings.

1. The degree of incisal overbite in the permanent dentition primarily was determined by the extent of mandibular forward growth which occurred during the eruption of the successional teeth. The lessened forward extent of the mandibular arch was responsible for a greater incidence of severe overbite in the mixed dentures.

2. The deciduous overbite was also a determining factor in that the slight overbite tended to increase during the period of the mixed dentition while a severe overbite became worse.

3. The definite overbite of the permanent dentition finally depended upon the eruption sequence of the permanent canines and premolars. If in the lower arch the sequence was canine, first premolar, second premolar and in the upper arch first premolar, canine and second premolar, the best results were observed.

4. Incisal overbite developed independently of the mechanism of molar adjustment.

A biometrical study of the development of the dental arches and occlusion in 60 children revealed the occurrence of several physiological mechanisms which influenced the final position of the teeth.

1. Considerable migration of the teeth concomitant with the eruption of accessional and successional teeth was observed to effect the increase in dimensions of the arches. Teeth and alveolar process thus are a genetic entity.

2. Observations made in this study endorse Brodie's principal concept that the development of the dentition is mainly based upon a congenital pattern. This pattern predetermines the spaced or closed arrangement of the deciduous arches and the positioning of the permanent tooth germs which seem to be of greater significance than function.

3. Differentiation between the manifestation of the general growth of the facial skeleton and that of the alveolar processes is conducive to a better understanding of the etiology of malocclusion and the development of certain paradentopathies.

4. Successful methods for preventive treatment may be instituted as a result of a thorough knowledge of the physiological migration of the teeth.