Cements continued resin

Both surfaces to be cemented should be clean and fit accurately to one another. A minimum continuous layer of cement should be applied to each surface to be joined. Where catalytic resins are used, provision should be made to hold the members in firm contact for the curing period. When contact cements are used, mechanical means are desirable to assure that the elements are in the proper position and orientation when they make the first contact... 

These resin cement systems require only moderate capital investment, yet can yield dramatic results. For example, the many thousands of cracks in the Los Angeles City Hall produced by the 1971 earthquake were repaired by the use of 20 thousand gallons of an aluminum and ceramic filled epoxy resin mortar.— Likewise, wood whose cracks have been sealed by polyurethane mortars is suitable for continuous lathe cutting for veneer manufacture. 

Ihe quest for interactive or bioactive dental restorative materials is not a totally new endeavor in dental materials. For example, as a general concept, glass ionomer cements (GICs) have been endorsed as a bioactive material because of their dynamic release of fluoride, as well as their unique mineral-based poly-salt matrix composition that is claimed to also contribute to the ability to remineralize calcium-depleted tooth structure. The continuous release of fluoride by GICs and resin-modified glass ionomers (RMGIs) has also been positioned as a potential mechanism to delay or inhibit secondary caries at teeth restored with these materials at the margins of the restorations [47,48]. 

A durable and popular composite, transite, was asbestos with up to 15% cement. In the form of boards and sheets, it was a substitute for wood, and in severe climates, was used for roofing, fence materials, and other structures because it weathers as extremely well. Transite with asbestos is no longer available. Its replacement, silica, has limited applications because of health concerns. Other composites are continuously being developed to serve the needs of industry. Other composites include linoleum (linseed oil and jute), Bakelite (phenol-formaldehyde resin and cellulose fiber), plywood, and vehicle tires. 

A smaller number of chemicals, known as sensitisers , invoke a response in the blood which produces dermatitis on continuing exposure. People who are thus sensitised become abnormally sensitive to the chemical and can develop severe reactions to its presence. Often, their only recourse is to exclude themselves from further work with or near the chemical substance. Cement, some wood types and resins are examples of sensitisers found in the industry. 

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