篩分法による咀嚼能率の研究

Abstract

For the purpose of measuring masticatory function by means of gravimetric sieveanalysis, it is important to study particle size distribution of masticated materials.The number and size of screens, the number of masticatory strokes, and the quantity of materials have relation to the distribution of particle size, and give different results for measurement. Japanese rice, which is the most suitable test material, was selected, and the effect of these factors were investigated by changing oral conditions, employing 10-, 16-, 32-, 60-, 120-, and 200- mesh screens. Results summarized are as follows :1) Particle size distribution is linear within standard error of 2%, when cumulative percentage oversize is plotted on the probability scale against the screen size on mathematical scale, in the following cases, namely complete dentition, molarsmissing, cases rectorated with crowns and bridges, and some cases of malocclusion, but such cases as full dentures and partial dentures don't give the linear correlation.2) Inclination of this line (coefficient of regression) correlates with the percentage oversize by 10- mesh screen (r=0.9), and equation of regression is characteristic in accordance with oral conditions, therefore percentage oversize of each screen can be calculated from that of 10- mesh screen.3) Particle size distribution is classified into 3 types, -denture-, normal-, and partial edenturous type, according to the coefficient of regression of this equation.4) The correlation between percentage oversize of each screen and the number of masticatory strokes is formularized by y = e-αt within standard error of 3%. “a, ” which iss constant, indicates chewing ability of each subject independent of the number of masticatory strokes (masticatory index) .5) Abovementioned rules are found to be independent of the quantity of test materials from 1 g to 4 g. Masticatory index by the same screen size is inversely proportional to the masticated quantity of rice.6) Masticatory efficiency is calculated by the ratio of masticatory index of each sub-ject to that of standard person, and it seems to be suitable unit to estimate masticating ability.7) Masticatory efficiency by each screen size gives different value according to the type of particle size distribution. By denture type efficiency takes the lowest value at 16-mesh screen, by edenturous type at 10- mesh screen, and by normal type each screen size gives almost equal value.8) The 10- mesh screen is most adequate to detect the rough difference of chewing ability of various oral conditions.