Calcium hydroxide is used in operative procedures such as pulp capping (protection for an exposed or nearly exposed pulp). It is available in premixed commercial preparations ready for immediate use. Because of its low crushing strength, calcium hydroxide alone is not used as an intermediate base. It is usually covered with zinc phosphate cement or zinc oxide and eugenol cement. Dycal, a commercial preparation, is an example of calcium hydroxide.
ROOT CANAL FILLING MATERIALS
Root canal filling materials consist of tapered gutta-percha or silver points in standard sizes that match the size of the files used. The points are cemented in place with root canal sealer that is usually a zinc oxide and eugenol preparation. Root canal filling materials are used to fill previously prepared root canals. They are a part of root canal, or endodontic, therapy.
a. Gutta-percha points are made from the refined, coagulated, milky exudate of trees in the Malay peninsula. Gutta-percha is pink or gray in color. It is softened by heat and is easily molded. When cool, gutta-percha maintains its shape. Gutta-percha points are used as a root canal filling material.
SILVER ROOT CANAL POINTS
a. Advantages. The dental officer has the option to use silver root canal points in filling a root canal.
CAVITY LINING VARNISH
Cavity lining varnish is used as a seal under an otherwise unbased restoration. It is composed of resins dissolved in a volatile thinner. Cavity lining varnish is used extensively to seal dentin tubules (small tubes in the dentin that contain dentinal fibers) and thus isolate the pulp of the tooth from the acidity of zinc phosphate cement. In some cases, it is used to help prevent marginal leakage around restorations. Cavity lining varnish is issued as a liquid in a container, usually together with a bottle of thinner. The bottle of varnish should be kept tightly sealed when not in use. If the varnish gets too thick, thinner is added to restore the original consistency. Copalite is the trade name for a common cavity varnish.
a. Dental porcelain is manufactured as a powder. When it is heated to a very high temperature in a special oven, it fuses into a homogeneous mass. The heating process is called baking. Upon cooling, the mass is hard and dense. The material is made in a variety of shades to closely match most tooth colors. Baked porcelain has a translucency similar to that of dental enamel, so that porcelain crowns, pontics, and inlays of highly pleasing appearance can be made. Ingredients of porcelain include feldspar, kaolin, silica in the form of quartz, materials which act as fluxes to lower the fusion point, metallic oxide, and binders. Porcelains are classified into high-, medium-, and low-fusing groups, depending upon the temperature at which fusion takes place.
b. High-Fusing Porcelains. High-fusing porcelains fuse at 2,400o Fahrenheit or over. They are used for the fabrication of full porcelain crowns (jacket crowns).
c. Medium-Fusing Porcelains. Medium-fusing porcelains fuse between 2,000o and 2,400o Fahrenheit. They are used in the fabrication of inlays, crowns, facings, and pontics. A pontic is the portion of a fixed partial denture, which replaces a missing tooth.
d. Low-Fusing Porcelains. Low-fusing porcelains fuse between 1,600o and 2,000o Fahrenheit. They are used primarily to correct or modify the contours of previously baked high- or medium-fusing porcelain restorations.
Tin Oxide. Tin oxide is used in polishing teeth and metal restorations. Tin oxide is a fine, white powder that is made into a paste by adding water or glycerin.
Pumice. Pumice is used as an abrasive and polishing agent for acrylic resins, amalgams, and gold. It consists mainly of complex silicates of aluminum, potassium, and sodium. Two grades--flour of pumice and coarse pumice--are listed in the Federal Supply Catalog.
Chalk (Whiting). Chalk is used for polishing acrylic resins and metals. It is composed primarily of calcium carbonate.
Tripoli. Tripoli is usually used for polishing gold and other metals. It is made from certain porous rocks.
Rouge (Jeweler's). Rouge is used for polishing gold and is composed of iron oxide. It is usually in cake or stick form.
Zirconium Silicate. Zirconium silicate is used for cleaning and polishing teeth. It may be mixed with water or with fluoride solution for caries prevention treatment. For full effectiveness, instructions must be followed exactly to obtain the proper proportions of powder to liquid.
|David L. Heiserman, Editor||
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Revised: June 06, 2015