[The first permanent molars and palatal or mandibular variations]

101 children, each of them with two teleradiographies, were selected. The first X-ray was taken at the time of the mixed dentition, the second one, when the permanent dentition was established. The purpose of the research is to show the oscillations of the palatine and mandibular planes, and their link to the movements of the first permanent molars. The palatine plane is found to swing between -7 degrees and +5 degrees with an average of -0.97 degree. The posterior part of that plane rocks downwards in 51% of the children. The limits are -7 degrees and -1 degree, with an average of -3.2 degrees. In 22%, the plane rocks upwards between +1 degree and +5 degrees with an average of +3.1 degrees. In 27% it moves parallel to itself. The posterior part of the mandibular plane varies between -6 degrees and +5 degrees, with an average of -1.1 degrees. It rocks downwards in 48% of the cases, between -6 degrees and -1 degree with an average of -3.9 degrees. In 22% of the children, this plane rocks upwards between +1 degree and +5 degrees with an average of +2.5 degrees. In 30%, it moves parallel to itself. The overall result is that the more the posterior part of the palate, or of the mandible moves downwards, the more the first permanent molars get straight or move forwards.