Genetic and environmental factors in the development of so-called pseudo- and true mesiocclusions.

Separation of genetic and environmental factors related to the development of so-called pseudo- and true mesioclusions was attempted and the classification, which is in common use in clinical orthodontics, reconsidered. A differential diagnosis of these two types of mesioclusions was made depending on whether or not the mandible slid forward into displacement by incisal guidance. By means of lateral roentgenographic cephalograms obtained from 66 pseudo- and 48 true mesioclusion patients and 52 control subjects, and their respective parents, the craniofacial morphogenetic characteristics of each mesioclusion were determined. A familial tendency to prognathic skeletal profile was noted in cases of both pseudo- and true mesioclusions. Nearly all of the significant morphogenetic differences between the two groups of patients with mesioclusion were related to environmental factors. The terms "pseudo" and "true" are probably misleading expressions for these mesioclusions.