John C. Bennett

The extraction–nonextraction dilemma as it relates to TMD

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.

Finishing with the preadjusted orthodontic appliance

Abstract With the preadjusted orthodontic appliance, there is a gradual progression toward finishing, rather than an abrupt stage of tedious wire bending. Therefore, the fewer the errors made as treatment progresses, the less work required during finishing. There are horizontal, vertical and transverse factors to be considered relative to finishing, as well as dynamic, cephalometric and esthetic factors. Horizontally, it is important to establish the correct tip of the anterior and posterior teeth. Adequate torque of the incisors must be controlled and all spaces should be closed, unless restorations are indicated. Vertically, crown lengths, marginal ridge relationships and contact points must be adjusted. Final correction of the curve of Spee must be established. Transversely, arch form and arch wire coordination must be set up, and posterior torque must be corrected. From a dynamic standpoint, the condyles should be in centric relation when the teeth occlude, and functional movements should be established. By this stage, habits should be corrected. And finally, cephalometric objectives should be reviewed, as well as esthetic objectives.