Abstract
This study is a continuation of“A Study on Statistics of Dental Caries”published in Japan Journal of Oral Hygiene, No. 1, Vol. 6, 1956.
Chapter I.
On the aggravation grade of caries, and the defective stage of dental substance, with special reference to“a scale for measuring the aggravation”.
We propose to use the following scale in order to measure the aggravation degree of caries. This scale has the advantage of being objective and quantitative, as compared with the usual classification which is subjective and qualitative.
i) volume of caries-capacity of defect in dental substance after the removal of soft dentine.
ii) carious surface, especially defect of masticating surface-defect of the surface of a tooth caused by caries, especially of the masticating surface.
iii) volume rate of caries=volume of caries/total volume of dental substance C1= (0-6) %, C2= (6-27) %, C3= (27-100) %, CM=100%
iv) rate of masticating surface defect=defect of masticating surface/total masticating surface C1= (0-5) %, C2= (5-100) %, C3=100%, CM=100%.
The author considers these characteristics will serve as the basis for the aggravation statistics of caries, statistics of dental ability, or evaluation of individual dental status.
Chapter II.
Statistics of caries aggravation
In Chapter I, we have pointed out the defects of usual statistics of caries aggravation, and having studied a method for ameliorating them, we have proposed a statistical measurement of caries aggravation.
In this Chapter we also derive diverse statistics from the proposed characteristics. As far as we know, no study in this field has yet been made; and this study is the result of the original idea of the author.
i) The following characteristics are used as the basis for measuring the aggravation grade of caries:
“volume of caries”,
“carious surface”,
“defect of masticating surface”.
ii) From these fundamental characteristics, eight following statistics are derived:
volume rate of caries,
defect rate of surface,
remaining rate of masticating surface,
aggravation velocity of caries,
aggravation rate of caries,
volume rate of healthy substance,
ability of masticating surface,
index of dental health and ability.
iii) These characteristics are calculating for all defective teeth, total teeth, by location and by person. Morever, we have also derived many statistics from them. The author belives these statistics are sufficient for the study of the process of caries.
iv) They will also serve as a convenient basis for comparing the resistibility of dentine against caries, a problem much discussed lately.
Chapter III.
Statistics of dental function, especially of the “ability of masticating surface”
We have studied the statistics of masticating ability, which is the most important part of dental statistics, and have also studied the ability of masticating surface which plays a fundamental role.
We have obtained the following conclusions:
i) It has become possible to classify the studies on masticating function into two groups, i. e., the one on ability, the other on efficiency. It seems to us the statistics on ability are less than those on efficiency. This is perhaps due to the difficulty and complexity of measuring.
ii) As the most important results on masticating ability, we may enumerate the calculation of contact point and surface by Dr. Yazaki, measurment of transparency of masticated wax plate by Dr. Manly, but all these studies on the decrease of masticating ability concern only with the change cause by a dental defect, and, as far as the author knows, no study has yet been made on the decreasing of masticating ability in the course of caries aggravation.
