[Protraction--it's use and abuse].
1. Protraction devices can be used to close excess spaces by moving posterior teeth forward, to protract maxillas, to rotate arch segments in cleft palate patients and to remove hyper anterior contacts in patients with TMJ derangements. 2. There are three types of protraction headgears: Chin support with cranial straps (Hickham), chin support with a forehead pad (Face mask) and zygoma support with a headband (Suborbital). They all have specific advantages and disadvantages. 3. The force magnitude from a protraction gear varies according to the desired effect from between app. 400 grams/side to move the maxillary anterior teeth forward and 800 grams/side to encourage maxillary sutural expansion. 4. The centers of rotation of the jaws and the dentition are located apically to the attachment of the protraction device. Therefore not only the intended mesially oriented force is produced but also the undesired side effect of both jaws moving around their centers of rotation. To avoid these negative effects the protraction elastics should always leave the arch in the canine area. 5. Basically Class III cases are due to either a short maxilla and/or a long mandible with variations in the vertical. App. 60% of all Class III cases have a short maxilla indicating the need for protraction. About 50% of the total Class III patient population would need surgery to finish with an ideal occlusion. However, many types of compromise treatments can be acceptable. 6. A good occlusion can only be accomplished in the presence of normal function. In Class III patients special attention should be given to possible nasal obstruction as well as to tongue posture and function. ENT cooperation and tongue spikes are often necessary to resolve these problems. 7. Class III elastics tend to rotate the maxilla and mandible counterclockwise. The resulting change in molar relationship is only due to the rotation of the occlusal plane which is unstable. Also because of the extrusional side effect there is an increase in vertical dimension which usually is undesirable. 8. Intraorally the protraction device can either be attached to a bonded acrylic expansion appliance or to a cemented Hyrax depending on the developmental stage of the dentition. To avoid traumatic occlusion conditions a modified splint should be used with the protraction gear in adults. 9. In all growing Class III patients overcorrection of overjet and overbite is very important. This way not only possible relapse is prevented but also the change of a posteriorly displaced mandible is avoided which could be a later cause for TMJ derangement. 10. When deciding whether the deformity is in the maxilla or in the mandible--the individualized Jacobson templates are very helpful.
Hickham
J H
JH
Poliklinik Nord, Freie Universität Berlin.
Miethke
R R
RR
D000293:Adolescent; D002648:Child; D003799:Dental Stress Analysis; D005115:Extraoral Traction Appliances; D005260:Female; D006801:Humans; D008297:Male; D008313:Malocclusion, Angle Class III / Q000628:therapy*; D011378:Prognathism / Q000628:therapy*; D012399:Rotation
Uber Gebrauch und Missbrauch des Frontalzuges.