叢生歯列を持つ者の歯牙と Basal arch の関係についての研究

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It is well recognized in the orthodontic practice that the ratio of the magnitude of the jaw bones relative to the full arrangement of permanent dentition should be within the range of 1.1 to 1.20. When the ration in a patient fell below this figure, there usually occur more or less an imbalance or so-called disharmony of magnitude between his jaw bones and his permanent dentition. In the clinic of orthodontic practice where patients with deciduous dentition are most frequeutly to be treated, it is desirable for the operator to have some criteria with which he could predict an exact magnitude which the permanent dentition and the jaws would respectively attain at definite future age of an patient. The future magnitude of one's permanent dentition may be predicted with reasonable accuracy by means of roentgenography of the teeth and other methods of measurement. Such prediction, however, is difficult with the future magnitude of the jaws because there is no available information as to the growth rate of jaws to be seen at these age stages of the patient. The present author undertook to study the growth rate of jaws on a total of 33 subjects consisting of 16 males and 17 females ranging in age from 6 to 15 by taking serial gnathostatic models from each subject for masurement. The data obtained showed that the mean increment in the magnitude of jaws of male subbjects amounted to 22±5mm and that of female subjects 21±5mm during the period of 9 years. This means that these subjects had a mean annual increment of 2.4mm of jaws through the 9-year period. The maximum and minimum values of the increment were shown to amount to 33 mm and 15 mm respectively during the same period. The study suggested that these figures would be of some help for the operator in predicting an approximate magnitude of jaws of a patient at his 15 years of age and thus would serve as criterion for tooth extraction in correcting the case of disrepancy.
1971-01-31

叢生歯列を持つ者の歯牙と Basal arch の関係についての研究

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