Fixed Orthodontic Appliances
Tooth movements with active spring components, which contact the tooth in a punctiform or linear fashion, are basically achieved by single-point and two-point application of force. Bodily tooth movement by multipoint application of force cannot be performed with removable active plates. Bodily tooth movements are only possible if the tooth is rigidly contained and this rigid mounting is pushed in the desired direction parallel to an additional guide.
Rigid mountings encompass the tooth to be moved with a broad steel band. A mounting is welded to this steel band. A guide splint can be incorporated into this mounting, with which the tooth is moved.
The technique for fixed appliances involves fixing prefabricated auxiliaries to the teeth to allow the forces to act on the teeth.These auxiliaries can be steel bands, which already have the necessary mountings or can be welded in the individual position. The outer surface of the bands has a high-glaze finish, and the inner surface is rough so that it can be cemented onto the teeth.
The prefabricated mountings are referred to as brackets and tubes. In addition, lingual cleats can be used, which are double hooks that are welded onto the lingual side of the band and can receive elastics.These auxiliary parts are welded onto the bands or, as is usually the case today, bonded or cemented directly onto the tooth surface.
The active components in this technique are spring hard stainless steel wires that are braided with a round or square cross section and have high elasticity. The wires are shaped into the ideal arch form that is to be achieved at the completion of treatment. The auxiliaries and wires are supplied ready-made; the bands can also be prepared by the practitioner. This means that it is possible to produce fixed appliances directly on the patient; they supplement or replace removable active plates in certain treatment situations. A brief outline of the operating principle is provided here so that dental technicians can undertake certain partial jobs involved in fabrication.
Modern multiband appliances are multipurpose fixed appliances that can be used to do the following:
- Eliminate tipping and crowding of individual teeth
- Translate teeth and groups of teeth mesially and distally
- Correct faulty positioning of individual teeth (eg, lifting partially or completely buried teeth into the dental arch)
- Shift teeth in parallel planes
- Eliminate dental arch deformations
- Balance occlusal discrepancies and differences in occlusal height
These are all anomalies of tooth position that can also be remedied with an active plate. However, fixed appliances are predominantly used in late cases or when an active plate cannot be worn.
The effect of fixed appliances is based on the elastic spring forces of wires and elastics as well as screw forces acting specifically on the teeth, periodontal tissues, alveolar processes, jawbones, and TMJs.