1969 Volume 11 Issue 4 Pages 116-119
In the published studies dealing with the growth processes of human teeth from the anatomic or embryologic approach, the usual means of expressing the development of their roots is in terms of years of individuals from their births [1-6].
In Particular, the permanent root with reference to its degree of development is often used as a unique criterion in the field of biometry and for this reason, there is known the concept of root age [7-12].
In connection with our 10-year consecutive survey of succedaneous and permanent dentition in the Japanese children [13-16], the authors have turned their attention to the fact that those teeth, I1, I1, Pm2, Pm2, which received undue stress in the period when their roots were still imperfectly formed will tend to result in abnormally shorter roots [16]. If the above finding is valid in all the cases, it follows that there will be created a definite ratiowise difference between the lengths of normally formed crown and root and those of abnormally formed crown and root under the conditions above specified, i.e., between those physiologically replaced by the successors and those replaced by abnormal ones having shorter roots.
The present study was conducted to see whether the above contention could be justified.
