A serial longitudinal cephalometric and dental cast study of growth and development in untreated class II, division 1 skeleto-dental malocclusions

Abstract

This investigation involves an appraisal of the growth and developmental changes that occur in untreated Class II, division 1 skeleto-dental malocclusions as derived from serial longitudinal cephalographic and dental cast measurements. The age range originated at 8 years and progressed at intervals to a maximum age of 13 years or over. Various angular and linear measurements were determined. Whereas SNA was found to be relatively stable, SNB and SNPog increased considerably with age without any concomitant self correction of the Class II molar and cuspid relationship. There was an inherent reduction of facial convexity. Not only do these findings dispute the concept of "the constancy of facial pattern" as proposed by Broadbent and Brodies but it also raises some interesting questions regarding the concept of differential growth. One would expect that if differential growth of the mandible were occuring, there should be some tendency toward self correction of the Class II interocclusal relationship. Some possible explanations for this paradox are presented in this study. A very significant correlation between changes at points B and Pog has been observed, indicating that alterations in one parameter are strongly accountable for changes in the other. A correlation of lesser, but interesting significance was determined between changes in SNB and SNPog in relation to the mandibular plane angle. It has some treatment implications which are discussed. Finally, the stability of the pterygomaxillary fissure as a reference landmark as proposed by Broadbent, Brodie, and Moore is critically questioned in the present study. Far too much change in its location with age was observed for this investigator to accept it as a stable landmark. Its use as a reference point from which to measure possible orthopedic movement of the maxilla is certainly questionable. With the prevailing interest in orthopedic correction at the time, more stable reference points such as implants must be investigated to determine its efficacy.