Extraction has been a controversial subject in the speciality of orthodontics for a long time. Some authors believe that the extraction of premolars leads to temporomandibular disorders because of collapse in vertical dimension. Over-retraction and retroclination of incisors cause the facial profile to flatten, bring about premature anterior contacts and displace the mandible and condyle distally. But numerous correlation studies in the literature do not support this contention. 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. Moreover, there is no evidence that premolar extraction causes higher incidence of temporomandibular disorders or undesirable flattening of the facial profile.
