Extraction has been a controversial subject for as long as the specialty of orthodontics has existed. Some authors believe that the extraction of premolars leads to temporomandibular disorders. This occurs, they say, because the vertical dimension collapses. Concomitantly, over-retraction and retroclination of the incisors cause the facial profile to flatten, bring about premature anterior contacts, and distally displace the mandible and mandibular condyle. Numerous correlation studies in the dental literature do not support this contention. There appears to be no higher incidence of temporomandibular disorders in patients treated with the extraction of premolars than in nontreated patients or those treated without extractions. Analysis of premolar extraction cases reveals that there is no collapse of the vertical dimension; on the contrary, the vertical dimension is either maintained or slightly opened. Similarly, there is no evidence that premolar extraction causes undesirable flattening of the facial profile. The facial profile established during treatment is primarily the result of diagnosis and treatment mechanics. Excessive anterior interferences resulting in possible posterior condyle displacement are the result of treatment mechanics. When arches are leveled properly and space closure and overjet reduction are adequately controlled, there is no reason that such interferences should occur.
R.P. McLaughlin is in private practice in San Diego, California
J.C. Bennett is Honorary Clinical Fellow in orthodontics, University of Bristol, and is in private practice in London, England