Principles and practice of operative dentistry . eral shakings allowed tosettle for a few days, when the clear fluid may be decanted off. If thesolution does not clear it should be filtered. (Flagg.) Mixing.—For mixing zinc oxychloride, or in fact any of the zinccements, a glass slab and a suitable spatula are necessary (Fig. 4G4).Upon the mixing-slab are placed one or two drops of the fluid, and near ita quantity of the powder. These are then incorporated and worked into athick creamy paste, and it is ready for use. The filling is introduced into 22 338 OPERATIVE DENTISTRY. the cavity by smal
Principles and practice of operative dentistry . eral shakings allowed tosettle for a few days, when the clear fluid may be decanted off. If thesolution does not clear it should be filtered. (Flagg.) Mixing.—For mixing zinc oxychloride, or in fact any of the zinccements, a glass slab and a suitable spatula are necessary (Fig. 4G4).Upon the mixing-slab are placed one or two drops of the fluid, and near ita quantity of the powder. These are then incorporated and worked into athick creamy paste, and it is ready for use. The filling is introduced into 22 338 OPERATIVE DENTISTRY. the cavity by small spatulas (Fig. 465), and adapted to the walls by meansof pellets of bibulous paper, which remove any surplus of liquid, and thushasten the setting. Characteristics and Properties.—Zinc oxychloride sets rather slowlyand is not so hard when set as the oxyphosphate cements. About fifteen min-utes are required for it to set sufficiently hard to allow amalgam to bepacked upon it without displacement, and half an hour to an hour for a Fig. Fig. 465. Bevelled edge (glass) raising-slab and spatula. gold filling. Some operators defer the operation of covering it with ametallic filling until a future sitting, protecting the cement with a gutta-percha filling until that time, in order that the cement may furnish aharder foundation for the metallic filling. When used in large masses it shrinks notably. It stands low in thescale as a conductor of caloric, and like all compounds which contain zincoxide, it is readily decomposed by the action of acidsand alkalies. Zinc oxychloride is not a definite chemical compound,and cannot be made by the method of mixing withoutone or the otherof the constituents being found in to C. S. Tomes, there is always free zincchloride to be found in the finished filling, and conse-quently the filling is hygroscopic. When freshly mixed, if it is brought into contact withvital soft tissues it is irritating and escharotic. Conse-quently
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