Figure 16-11. Removable space maintainer. (2) Fabrication procedures. (a) Bands may be adapted by the dental officer intraorally and sent to the dental laboratory seated in an impression or on a cast. Bands A may also be adapted on a working cast by the dental prosthetic specialist. (b) The wire or bar is adapted according to the design on the DA Form 2868. (c) The components are soldered or welded together. (d) The older joint is finished and polished. 16-5. Interceptive Orthodontic Appliances a. Removable Space-Regaining Appliance (fig 16-13). (1) Description and use. The removable space regaining appliance is a Hawley retainer with a double helical expansion spring added to the appliance. It is used to regain space lost by the premature extraction of permanent or primary teeth. (2) Fabrication procedures. A double helical spring is fabricated and positioned on the cast. The rest of the appliance is fabricated the same as the Hawley retainer. b. Fixed Space-Regaining Appliances. (1) Banded jackscrew appliance (A, fig 16-14). A. CANTILEVER LOOP SPACE MAINTAINER. C B. DOUBLE BAND SPACE MAINTAINER. B C. CANTILEVER SINGLE BAR SPACE MAINTAINER. THE TERMINAL TIP OF THIS APPLIANCE REACHES SUBGINGIVALLY TO MAINTAIN THE SPACE. IT MAY BE MODIFIED TO PREVENT EXTRUSION OF OPPOSING TEETH. Figure 16-12. Fixed space maintainers. the most distal band. The jackscrew is welded or soldered to the distal band. The appliance is finished and polished. When properly constructed, the jackscrew can rotate inside the tube on the most mesial band. (2) Multiple-banded loop appliance (B, fig 16-14). (a) Description and use. The multiplebanded loop is used for stabilized pressure and control to regain or maintain posterior space by gradual modification of the loop curvature. (b) Fabrication procedures. 1. Banding techniques are the same as for the band loop space maintainer. 2. The wire is adapted to the facial surfaces of the bands. The wire has a loop sagging gingivally from the horizontal. The size of the loop is determined by the amount of movement desired. pleted. 3. The soldering or welding is done. 4. Finishing and polishing are com c. Space-Closing Appliance (fig 16–15). (1) Description and use. This orthodontic appliance is used with rubber ligatures to obtain some bodily tooth movement. (2) Fabrication procedures. (a) Banding techniques are the same as for the band and loop space maintainer. (b) An open end tube and hook, facing distally, is soldered or welded facial and lingual to the main anchor-banded tooth. Guiding wires are placed into the tubes and welded or soldered to the banded tooth to be moved. Hooks facing mesially are also welded or soldered on the banded tooth to be moved. Rubber elastics are then placed onto the hooks to obtain movement. 16-6. Trimming and Finishing Orthodontic Casts a. General. Orthodontic casts are trimmed and finished differently from removable partial dentures and complete denture casts. The base and land areas are trimmed so that the heels of the maxillary and mandibular casts can be positioned on a flat surface with the teeth in centric occlusion. They can also be turned on the right or left side and the teeth will remain in centric occlusion (fig 16-17). b. Trimming and Finishing Procedures. (1) Irreversible hydrocolloid impressions are poured as usual, using plaster or stone as directed by the dental officer. (2) Any excess material is removed from the heels of the mandibular cast with a plaster knife until the cast can be placed on a flat surface with the incisors and terminal molars touching the surface. (3) The mandibular cast is placed on the right angle guide plate with the teeth touching the plate side and the bottom of the cast toward the wheel. A damp, folded paper towel is placed between the guide plate and teeth to prevent chipping. (4) The bottom of the mandibular cast is trimmed until it is parallel with the occlusal plane. (5) The mandibular cast is removed from the right angle guide plate and the bottom of the cast placed on the trimming table so that the back of it can be trimmed. (6) The back part is trimmed with 12 mm of the terminal molar. If it is a class III type malocclusion case or if the maxillary second molars are erupted and the mandibular ones are not, more than 12 mm can be left behind the terminal molar on the mandibular cast. If asymmetry exists, a line is drawn from the midline of the mandibular arch to the back of the cast. The trimming is done at right angles to this line leaving more behind one molar than the other. (7) The maxillary cast is occluded with the trimmed mandibular cast. A wax interocclusal record is used to assure a centric relationship. Some plaster may have to be trimmed from the heels of the maxillary cast to obtain occlusion. (8) With the casts in occlusion, the base of the mandibular cast is placed on the trimming table with the back towards the wheel. The maxillary cast is trimmed until the grinding wheel just touches the back of the mandibular cast. This should allow the casts to be placed on their backs on a flat surface and remain in occlusion. This area is finished on a fine grit wheel. (9) With the casts setting on their backs and in occlusion and using the right angle guide, the top of the maxillary cast is trimmed until it is parallel to the bottom of the mandibular cast. (10) The back of the cast is placed against the angulator guide and one side is trimmed to the deepest part of the mucobuccal fold. This is repeated for the other side. The angulation for the mandibular cast is 55°. (11) The angulator guide is placed next to the shield of the cast trimmer and the heels are trimmed to 6 mm. distance from the distobuccal cusp of the terminal molar. The heels should be equal in length. (12) The front of the mandibular cast is trimmed parallel to the back. This is trimmed until the depth of the fold in the central incisor area is reached. Then the corners are rounded until an evenly rounded symmetrical front is obtained. This is usually done without any guides. (13) Steps 10 through 12 are repeated using the fine grit wheel. |