In order to know how much the teeth which had undergone the pulp extirpation have recovered their masticatory function, i. e. for the evaluation of clinical effect of the treatment, it is most logical to measure directly the individual biting force of each tooth concerned. For this measuring, the author selected 825 male and female patients, from 20 to 39 in age who had the crown restored teeth (number of them: 3, 175), without any subjective disturbances after the treatment, possessing the masticatory function satisfactorily at the time of the survey. These teeth with the good clinical effects were divided into A and B groups, in which 1, 871 teeth in Group A (radiographic normal), and other 1, 304 teeth in Group B (radiographic periapicosis to be described in 6).
Individual biting forces of these teeth in two groups were separately measured by the use of the biting force measuring apparatus with four strain guages attached. For controls, individual biting forces were additionally measured on each of the intact teeth same-named as those in groups A and B. Consequently, when the individual biting force (means) of each tooth of the lower and upper jaws is observed in males and females in the age groups of 20's and 30's respectively, there is no significant difference between both ages or sexs. For this reason, the age and sex distinctions were ignored in the treatment of data in the three groups. Based on the means of those measurments in the three groups, the author obtained the following conclusions.
1. Respective individual biting forces of Controls, A and B groups are as follows.
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2, Individual biting forces of teeth in Group A are smaller than those in controls, and those in Group B are still much smaller.
3. When individual biting forces in Groups A and B are compared with those in controls in terms of each tooth, the fact is noted that though there is a decrease from 2 to 10% in the upper anteriors in Group A, there is no significant difference between them and controls. On the other hand, as regards other teeth there is definitely a significant difference between them and controls, with a decrease being anywhere from 12 to 19%. In paticular, a marked decrease in individual biting forces is observed in the lower incisors with as much as 20 %.
Also in Group B, individual biting forces are reduced by as much as 25 to 38 %, and there is observed a significant difference between them and controls. This is particularly noteworthy in the lower incisors, where the reduction is as much as 44%.
4. When the reduction of individual biting forces of teeth in both Groups A and B against those of controls is observed as regards the same-named teeth on the upper and lower jaws, it is found that in Group A its rate of 21/12 is more than that of 21/12, whereas in Group B that of 54/45 is more than that of 54/45 with a significant difference in each pair. As regards other teeth in Group A and B, however, there is observed no significant difference between upper and lower same-named teeth.
5. When the reduction of individual biting forces in Groups A and B as regards the samenamed teeth on the right and left sides of jaw is observed, there is no significant difference between them in the both groups.
6. When individual biting forces in Group B as regards the radiographic findings of their periapical tissues are observed, individual biting forces of those teeth accompanied with the findings of the rarefaction of trabeculae are generally reduced more than that of those teeth, which give the findings of the widening at their periodontal spaces.
However, there is no agreement between, in the cases with similar radiographic appearances, the degree of the spread of affected area and that of reduction in the individual biting force concerned.
7. There is calculated no significant interrelation between the number of years after pulp extirpation and the individual biting force concerned.

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