A new method of using cephalometric measurements in orthodontics (part 2) or how standard deviations can be the practitioner's false friends

It is generally agreed that cephalometric analyses of the Americans Ricketts, Steiner, and Tweed are of questionable utility. The C.R.A.N.I.O.M group has formulated a new method of using cephalometric measurements that it believes will be moderately helpful to orthodontists in making their diagnoses. We analyzed 83 young adults in Class I occlusion who had had no orthodontic treatment. The most interesting new formulation of our plan was to examine the extremes of the variables that we considered in this population. These figures constituted limits that differed widely from each other: there was more than a 30 � gap between the measurement of the incisor inclined furthest buccally and the one inclined most lingually (or palatally). Accordingly, for these lower anterior teeth inclinations to Downs’s mandibular plane ranging from 78 to 114 � were acceptable. And for the maxillary incisors inclinations to the Frankfortplanevarying from97.5 to 130.1 � are consideredto be in a standard range. The need to reposition incisors in order to conform to what we can now see as an abusively rigid normal accordingly occurs much less frequently. For this reason, orthodontists will find far fewer indications for the extraction of bicuspid teeth than they would in rigidly adhering to the standards imposed by the Ricketts, Steiner, and Tweed cephalometric analyses. We believe that measurements of skeletal, osseous structures merely differentiate between various typologies and do not describe forms that constitute anomalies. The C.R.A.N.I.O.M group affirms that cephalometrics occupies a position in the array of orthodontic diagnostic tools that comes after the assessment of esthetic, periodontal status, and muscular equilibrium.