Zinc phosphate cement applications

Materials that are compatible with biomtneralized phosphates (see Section 7.2) may be useful for implants A variety of synthetic calcium phosphates have been investigated. Ca3(P04)2 can be used as a biodegradable bone implant, which is gradually replaced by autogenous bone, and less degradable apatite implants can attach to natural bone without inflammation. Bioinert zinc phosphate cements are used in prosthetic dental applications. 

It is used for luting, lining and as a periodontal pack. Indeed, it can be used to replace the zinc phosphate dental cement in all applications with the possible exception of post crowns (crowns which are placed on a metal post placed in the tooth root) and cantilever bridges (Smith, 1982a). 

Considerable development has occurred on sintered ceramics as bone substitutes. Sintered ceramics, such as alumina-based ones, are uru eactive materials as compared to CBPCs. CBPCs, because they are chemically synthesized, should perform much better as biomaterials. Sintered ceramics are fabricated by heat treatment, which makes it difficult to manipulate their microstructure, size, and shape as compared to CBPCs. Sintered ceramics may be implanted in place but cannot be used as an adhesive that will set in situ and form a joint, or as a material to fill cavities of complicated shapes. CBPCs, on the other hand, are formed out of a paste by chemical reaction and thus have distinct advantages, such as easy delivery of the CBPC paste that fills cavities. Because CBPCs expand during hardening, albeit slightly, they take the shape of those cavities. Furthermore, some CBPCs may be resorbed by the body, due to their high solubility in the biological environment, which can be useful in some applications. CBPCs are more easily manufactured and have a relatively low cost compared to sintered ceramics such as alumina and zirconia. Of the dental cements reviewed in Chapter 2 and Ref. [1], plaster of paris and zinc phosphate... 

Historically, two acid-base cements were used in dentistry, their use dating back to the late 19th century. These were the zinc phosphate and dental silicate cements [7], These two remained in clinical service until at least the 1970s, and zinc phosphate continues to be used today, with its principal application being the luting of crowns [2],... 

These cements are based on the reaction product of phosphoric acid with other materials, such as sodium silicate, metal oxides and hydroxides, and the salts of the basic elements. Zinc phosphate is the most important phosphate cement and is widely used as permanent dental cement. It is also modified with silicones to produce dental-filling materials. Compressive strengths of up to 200 MPa are typical of these materials, which are formulated to have good resistance to water. Copper phosphates are used for similar applications, but they have a shorter useful life and are used primarily for their antiseptic qualities. Magnesium, aluminum, chromium, and zirconium phosphates are also used. ... 

Dental cements are a diverse class of material of widely different chemistries and applications (2,3). However, all may be classified as acid-base reaction cements formed by mixing a powder(base) with an acidic liquid. A typical example, the traditional zinc phosphate, is the product of the reaction between a zinc oxide powder and a concentrated solution of phosphoric acid. The cement sets, within minutes, as an amorphous zinc orthophosphate gel is formed. 

One great advantage with phosphate bonded ceramics in biomaterial or dental applications is the phosphate ions in their structure. Bones contain calcium phosphate, and hence phosphate bonded ceramics are generally biocompatible with bones. While chemically bonded calcium phosphate ceramics have been difficult to produce, magnesium and zinc based phosphate bonded ceramics have been more easily synthesized and used as structural and dental cements. 

Enriched in many zinc ores, hlack shales, phosphatic shales. Can he enriched in soils, sediments, and waters affected hy emissions from smelters, power plants agricultural applications of sewage sludge mining and industrial wastes and hy-products industrial wastes, hy-products, and trash (i.e., battery production, leather tanning, electroplating, cement use). 

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