THE EFFECTS OF EXTRACTION VERSUS NONEXTRACTION ORTHODONTIC TREATMENT ON THE GROWTH OF THE LOWER ANTERIOR FACE HEIGHT

The effect of orthodontic treatment on the lower anterior face height (ANS-Me) is of fundamental importance to the orthodontist. However, the choice between the two main methods of treatment, extraction versus nonextraction, is not clear cut. It is believed that the extraction method decreases ANS-Me, whereas nonextraction methods result in an increase in ANS-Me. This study examined the effects of both methods on ANS-Me for a sample of 174 subjects divided equally between Class I and II malocclusions. Most studies controlled for growth by using subjects in the same age group. However, we controlled for the effects of growth by normalizing ANS-Me measurements to the Michigan Growth Standard. With this method, we can compare subjects who differ in terms of the age at which treatment was started, as well as subjects whose treatments were of different duration, thereby enlarging the sample size. In addition to growth and duration of treatment, other factors like the effects of treatment choice and treatment mechanics were considered. The results obtained show that nonextraction treatment in Class I and II subjects is associated with a significant increase in the lower anterior face height. However, extraction treatment is not associated with any significant change in ANS-Me.