378 CHARLES R. STOCKAED AND A. L. JOHNSON 



skulls tend to have various types and degrees of malocclu- 

 sion, increasing in severity in almost direct proportion to 

 the shortness of the skull. 



This definite relation between the total shape of the head 

 and the perfection of dental occlusion made it seem desirable 

 to chart several regional indices for these skulls in order 

 to determine what portions of the skull are most largely 

 concerned with the disturbances of dental occlusion. Logically, 

 of course, one would suspect the muzzle or facial region of 

 being mainly concerned, but whether all parts of the muzzle 

 are equally involved, and whether any other skull proportions 

 play a role in these maladjustments, were points to be de- 

 termined. 



to — li III | , llHl 



»-||| Illll:. lllllli lllllllllllllll ,: Ill II 



111 





A B C D E F G 



Text-figure 7:;. Relation of dental occlusion to cranial index in 184 skulls 

 divided into groups as indicated in text-figure 72. 



The cranial index (relation of cranial width to length) for 

 the skulls in each of these seven occlusal groups is charted 

 in text-figure ?.">. The forty-nine skulls with normal occlusion 

 range in value for this index from 84 down to 47, and the 

 six groups with various degrees of malocclusion all fall al- 

 most exactly within this range. This figure clearly indicates 

 that there is no significant relationship between width-length 

 proportions of the cranium and proper dental occlusion in 

 these skulls. It therefore follows that the definite relation 

 between the value of total skull index and type of occlusion 

 must be due almost entirely to differences in facial propor- 

 tions. 



The muzzle index, width across maxillary canines relative 

 to distance from nasion to tip of premaxilla, represents an 



