乳歯晩期残存例の統計学的観察

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  • Statistical Observation on the Multiple Cases (106 Cases) of the Retained Deciduous Teeth
  • ニュウシ バンキ ザンソンレイ ノ トウケイガクテキ カンサツ
  • 乳歯晩期残存例の統計学的観察 : 主論文の要旨

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Macroscopic, roentogenological and statistical examinations of 106 cases (151 teeth) with the retained deciduous late in life, from 14 to 47 in age, were conducted. At the same time, histological examinations were made of a portion of the retained deciduous teeth by making section preparations after extractions. Furthermore, a statistical analysis was made of the materials on a total of 899 cases with 1, 756 teeth : 793 cases with 1, 605 teeth of the retained deciduous teeth in the Japanese collected to date since 1919 by the Department plus those by the author. The relations between missing of the permanent successors related to the retained deciduous teeth and resorption of the deciduous teeth root, and the relations to the terminal reduction of tooth were discussed. The results were as followes : I. On the 106 cases (151 teeth) 1. Frequency of appearance by the kind of tooth : As reported by the others, the second deciduous molars (hereinafter called E) showed the highest frequency (52%), followed by the deciduous cainine (24%, called C) and the deciduous central incisor (11%, called A). Both the deciduous lateral incisor (called B) and the first deciduous molar (called D) showed about the same with less than 10%. By the jaw, A and E had a tendency to appear more in the mandible, and B and C in the maxilla. 2. Case distribution by age : The late teens and the first half of the twenties showed the highest frequency and accounted for 70%. There were 3 cases in the forties. 3. Cases by the number of teeth : The cases of one-tooth were the highest with 67 cases (63%), two-teeth cases 34 (32%). Of the latter, 33 cases were of horizontally symmetrical cases. Of these, the most frequent was E (mandible) followed by A (mandible) and C (maxilla). 4. The retained deciduous teeth on the whole were implanted solidly. The incisal edge or the occlusal surface showed rather extensive attrition. Among the deciduous molars, amalgam fillings, inlays, onlays and metal crowns mounted were observed. 5. In the roentogenograms, the dental germs of the permanent successors under all the deciduous teeth were missing. Resorpted roots were comparatively few. 6. Observation of the section preparations revealed minute resorpted lacunae, not distinguishable in the roentogenograms, scattered on the whole surface of the root. II. On the materials on a total of 899 cases (1756 teeth) 1. Frequency of appearance by the kind of tooth : E showed the highest frequency with 48.5%, followed by C (24.2%), D (9.8%), A and B (8.8%). By the jaw, the orders were E, C, B, D and A in the maxilla, and E, A, C, D and B in the mandible. By the sex, B was predominant in the maxilla for the female. 2. Case distribution by the age : The highest frequency was in the range from the late teens to the first half of the twenties, accounting for 64%. There were 24 cases (2.9%) in the range from the forties to as high as 75 years of age. 3. Cases by the number of teeth : The cases of one-tooth case were the highest with 537 cases (64%). Two-teeth cases were 181 cases (22%). Of the latter, 140 cases were symmetrical either horizontally or vertically. By the teeth, E was the highest, followed by C and A. The cases with seven-teeth to all the deciduous (20 teeth) numbered 24. 4. Of the 1, 186 teeth subjected to roentogenological examinations, there were 1, 058 teeth (89%) with the permanent successors missing and 88 teeth (7%) with the permanent successor coexisting.

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