Most orthodontists take lateral skull X-rays about the age of 12 to 14 to establish the position of the maxilla and mandible in relation to the cranium as a whole. X-rays have been used for this ever since Brodie showed (1938) that the skeletal form was more or less set by that age. Treatment was not recommended before then because experienced showed it tended to relapse.
Orthotropics suggests that most skeletal malformations are due to adverse oral posture; mainly leaving the mouth open and tongue-between-tooth habits and the emphasis of diagnosis is moving to studying oral posture. This is difficult to recognise using X-rays until after the damage has occurred although photographs can be used to forecast facial growth from the age of three or four (see illustration).
With experience anyone can be taught to read the muscle posture of the tongue and lips from the face itself and their effect on developing facial form. A photograph will demonstrate this but not an X-ray. Changing oral posture can create large changes in a growing face provided the child is under the age of seven or eight, but of course the postural changes must be maintained afterwards if a permanent correction is desired (see illustration).