VARIABILITY OF THE FORM OF MAXILLARY PERMANENT INCISORS

¹ Northampton, England

1. A new method of measuring the shape and size of maxillary first permanent incisors has been suggested by using (1) the labial surface area, (2) tooth width index, and (3) the taper (angle at which the mesial and distal sides converge).

2. Fifty modern English teeth have been measured and it has been shown that the data may be presented either by mean and standard deviations, or in the form of groups read off from the distributions plotted on arithmetic probability paper, and then combined together in a 3-way table giving 27 different types.

3. The present results show considerable differences when compared with other racial groups in the literature, but similarities with my own Saxon data.

4. It is shown that the form of these teeth is little affected by environment, but is the result primarily of heredity and is therefore a suitable character for genetic analysis.

5. The method can be extended to other teeth by means of coordinate transformations, and an example is given.