継承歯を欠如した晩期残存第2乳臼歯の咀嚼能力に関する研究

抄録

The seventy persons (38, 32), who were between 20 and 28 years old and had late persistent second deciduous molars, were found in 28, 580 people over the age of 20 (16, 830, 11, 750), who were examined at random.
On those subjects and the 143 late persistent second deciduous molars had, the author conducted clinical examinations, roentgenograms, measuring the individual biting forces and the comparison of those on one side in a person and those of the second permanent premolars on opposite.
For measuring biting forces, the biting forces measuring appartus with four strain gauges attached and Multiplex monitor-recorder (RM-150 type) made by Nihon Koden co. were used, and the following results were obtained.
1) The seventy subjects with those deciduous molars were found in 28, 580 people exmined. It is ratio to the total number of the people examined was 0.25 per cent.
2) Those subjects were 38 men from 16, 830 examined and 32 women from 11, 750. It is ratio to the total number was 0.23 per cent in male and 0.27 pe cent in female. But there is no significant difference between in male and female.
3) The subjects with two persistent molars to the total number of the subjects were about 66 per cent, those with one about 20 per cent, those with four about 10 per cent and those with three about 4 per cent, least.
4) When observed the kind of the late persistent second deciduous molars, the following finding were obtained.
E. 32 (22.4 per cent) E. 36 (25.2 per cent)
E. 39 (27.3 per cent) E. 36 (25.2 per cent)
There were no significant difference between those.
5) The late persisent second deciduous molars without second permanent premolars to the total number were141/143 (98.6 per cent) and those with second permanent premolars were 2/143 (1.4 per cent).
6) When the relationships between maxilla and mandibule, and right and left sides of jaws were observed based on #4 findings, the late persistent second deciduous molars were found 47.6 per cent in maxilla and 52.4 per cent in mandible. There was no significant difference between those. And there was also no significant difference in per cent of the persitent molars between right and left sides of in maxilla and in mandible.
7) The subjects for either type of E/E and E/E to the total number of the subjects were 21.4 per cent (15/70 in number), 10.0 per cent (10/70 for either type of E/E and E/E E/E 8.6 per cent (6/70) for either type of E and E, 5.7 per cent (4/70) for E/E types, 4.3 per cen (3/70) for either type of E/E and E/E/E, 2.9 per cent 2/70 for E/E type and 1.3 per cent (1/70) for either type of E and E.
8) The individual biting forces of the persistent molars, when observed by each group, were as follows.
The mean value of the individual biting forces of each persistent molar in group [A] (male and female involved), which is vital, and without dental caries and any restorations except light attrition, and has neither resorption of dental root nor permanent premolars in roent genograms, was as follows:
E: 36.7Kg, E: 35.2Kg, E: 37.7Kg, E: 37.1Kg
There was no significant difference in biting forces between maxilla and mandible, and between right and left sides of jaws, among the four values above.
Then mean value of the individual biting forces of each sex was as follows:
E: 38.1 Kg 34.9 Kg
E: 36.0 Kg 34.3 Kg
E: 38.9 Kg 36.4 Kg
E: 39.1 Kg 35.3 Kg
There was a tendency which the biting force in male was greater than in female, but no significant difference was found between them. And also there were no significant differences between kind of tooth, and in maxilla and mandible, and right side and left side.
9) The individual biting forces of the late persistent second deciduous molars which were restorated with amalgam, gold inlay and gold crown were about 5-7 Kg less than those of #8 findings.