A practical treatise on mechanical dentistry . screw-head may be covered with amalgam, cement, or gold, asdesired. As a preferable mode, however, the screw-post may first befixed in the root, the crown adjusted over the post, amalgampacked on the root and around the post, the crown seated firmly,more amalgam packed in the crown cavity around the post, andthen a nut screwed on the post, as shown in Fig. 341. In all thesectional cuts cement, amalgam, or gutta-percha is to be understoodas filling the cavities in the conjoined roots and crowns. Fig. 342 shows in contour a dovetailed crown mounted
A practical treatise on mechanical dentistry . screw-head may be covered with amalgam, cement, or gold, asdesired. As a preferable mode, however, the screw-post may first befixed in the root, the crown adjusted over the post, amalgampacked on the root and around the post, the crown seated firmly,more amalgam packed in the crown cavity around the post, andthen a nut screwed on the post, as shown in Fig. 341. In all thesectional cuts cement, amalgam, or gutta-percha is to be understoodas filling the cavities in the conjoined roots and crowns. Fig. 342 shows in contour a dovetailed crown mounted on asuperior molar root in the manner shown by Fig. 335. It isobvious that the crown of Fig. 335 might be ground quite downto the post ends, and yet be firmly held by the dovetail sides ofthe central cavity. The Gates Crown.—The Gates crown is quite similar to the ARTIFICIAL CROWNS. 495 Bonwill crown. It is usually attached to the root, however, by ametallic screw manufactured for the purpose, such as is illustrated Fig. Fig. 344. in Fig. 344, instead of the Bonwill pin. The screw is first insertedin the root and the amalgam packed around it. In nearly all roots,at a reasonable distance up the canal, a suitable place for fasteningthe end of the screw can be found. Too much forcemust not be applied in its insertion, as a root is easilysplit. In bicuspid and molar crowns nuts are used onthe screws, which fit slots in the grinding surface ofthe porcelain. They are screwed into the amalgam orcement, and covered with it in the process of cementa-tion of the crown. The Foster Crown.—The Foster crown also resem-bles the Bonwill, but has less concavity at the base. The crown isattached to the root by a headed screw (Fig. 346) or a screw witha nut, instead of the Bonwill pin. Fig. 345. Fig. 346.
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectdentist, bookyear1903
