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Summary. In results obtained in clinical impressions used to make the model






In results obtained in clinical impressions used to make the model. The accuracy of the plastic crown depends on the strength of the material used for the model. Preference is given to the strongest varieties of gypsum – marble, super and others, as well as cement (combined model). For the manufacture of the last of the phosphate cement to form imprints teeth, which are planned to crown. Then inserted into the uncured cement angled wire thickness of 1.5 mm for a better connection with the plaster, and you fill the entire print.

Assessing the quality of the working model, paying special attention to the accuracy of display gingival sulcus. The current practice of engraving neck of the tooth in any way cause damage to plaster and inaccurate resulting printout. In this regard, it should be recognized the most promising method is not engraved neck and cutting the gingival margin to the deepest of its footprint in the gingival sulcus. After preparation of the cervical part of the tooth, aimed at ensuring a minimum immersion edge plastic crowns in gingival groove (less than 0.5 mm), anatomical modeling exercise using a colorless wax. Wax reproduction of the future artificial crown made larger in volume, based on the plastic trim after curing, restoring with close contact with the antagonists and standing side by side with his teeth.

Abutment with a wax reproduction of artificial crown cut from a plaster model with standing side by side with his teeth as a block. Conically cut adjacent to the wax model plaster teeth, and the whole block of gypsum plaster in a special flask one of the ways (direct, indirect or combined). The best way should be recognized when the abutment is located in the flask vertically. This reduces the likelihood of break off a stone stamp in molding plastic test. The surface of the hardened plaster smeared Vaseline oil, place the top of the flask and fill it with plaster. Flask with hardened plaster is placed in boiling water for 10-15 minutes and then opened.

Remnants of melted wax carefully wash with hot water and cooled cuvette. For plastic crowns apply domestic plastic " Sinma-74", " Sinma-M", " Sinma-M+V". Plastic is available as a powder-liquid set.

Plastic crown can be made two-tone. It is known that in the neck tooth has a yellow tint than the cutting edge. Sometimes the cutting edge of the crown is very light color, almost transparent. In this case, making a monochromatic crown does not give the desired result.

To make a two-tone crown, plastering should be done so that the entire vestibular surface was opened. Plastic mix the two colors, the color of the tooth, marked in color. Molding is carried out, as mentioned above, the color, which is the core. Strictly consistent mode of polymerization, plastic crown is released from the flask, is removed from the surface of the remains of plaster, trim, grind and polishes, to adjustments of the mouth is stored in water.

Removing the crown is made from the cell after unscrewing the clasp. Then, in the interval between the base of the cell and enter Contra Refractive spatula or knife for plaster and lever-like usually easy to divide the movement of the flask. Removing the flask, make a circular incision with a knife in the direction of plaster to the walls of the flask and remove the prosthesis with covering it with plaster. It is better to use for this purpose a special press, especially in mass work. Remains of plaster were removed in cold water with a stiff brush, wipe dry with prosthesis and start to finish.

Finishing, grinding and polishing of the plastic crown.

Finish produced with a file, preferably with a large semi-circular notch, as well as special knives - graver and scraper. The latter have the form of spoons of different sizes with sharp edges. Graver are straight, pointed, triangular and semicircular.

It should be noted that the aforementioned tools currently are not used, including finishing dentures. They drove all over the place various drills and cutters.

After careful finishing the prosthesis should be roughened with sandpaper and abrasive materials that were not even scratched. Polishing can be done by hand and grinding motors. In the latter case, a special holder for sanding paper is inserted into the tip of the grinding motor. A strip of emery paper is inserted into the device, which resembles a disk-holder, but instead of a propeller cut, and while rotating the paper wind on at him and makes grinding. We should be careful not to strain the prosthesis occurred due to heating. The final grinding and polishing to produce fortified in grinding-motor by felt various forms, beginning with the cone. Then, instead of felt grinding-motor inserted into a stiff brush and constant lubrication of the surface of the prosthesis gruel abrasive continue grinding.

After polishing the crown washed with a brush in cold water and polish with a soft bristle brush with diluted in water with chalk or gypsum (you can stir in vegetable oil).

Technique of manufacturing of a temporary plastic crown:

After tooth preparation remove a print, cast plaster model. On plaster model the plastic tooth picked up for color in the form of a thin plate from the vestibular part is established. All remained parties cover with self-hardening plastic, which well incorporates to the picked up tooth. On processing of such temporary crown time small amount is required. Fix a crown on temporary cement. Such temporary crown not only protects tooth from irritants, but eliminates also the esthetic lack arising after preparation of tooth.

Thus, it is necessary to consider aseptic, antiseptic, physical and chemical protection of a naked dentine obligatory, as the tooth processed under a crown is a live and vulnerable fabric.


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