instillation of crowns, bridges, inlays, onlays, and orthodontic appliances. composition: powder + liquid reaction zinc oxide (powder) + poly(acrylic) acid (liquid) = zinc polycarboxylate zinc polycarboxylate is also sometimes referred to as zinc polyacrylate or zinc polyalkenoate components of the powder include zinc oxide, stannous fluoride, magnesium oxide, silica and also alumina components of the liquid include poly(acrylic) acid, itaconic acid and maleic acid. adhesion: zinc polycarboxylate cements adhere to enamel and dentine by means of chelation reaction. indications for use: temporary restorations inflamed pulp bases cementation of crowns advantages disadvantages bonds to tooth tissue or restorative material difficult to mix long term durability opaque acceptable mechanical properties soluble in mouth particularly where stannous fluoride is incorporated in the powder relatively inexpensive difficult to manipulate long and successful track record ill-defined set zinc phosphate cements zinc phosphate was the very first dental cement to appear on the dental marketplace and is seen as the “standard” for other dental cements to be compared to. the many uses of this cement include permanent cementation of crowns, orthodontic appliances, intraoral splints, inlays, post systems, and fixed partial dentures. zinc phosphate exhibits a very high compressive strength, average tensile strength and appropriate film thickness when applies according to manufacture guidelines. however the issues with the clinical use of zinc phosphate is its initially low ph when applied in an oral environment (this linked to pulpal irritation) and the cements inability to chemically bond to the tooth surface although this hasn't affected the successful long term use of the material. composition: phosphoric acid liquid zinc oxide powder formerly known as the most commonly used luting agent. zinc phosphate cement works successfully for permanent cementation, it does not possess anticariogenic effect, not adherent to tooth structure, acquires a moderate degree of intraoral solubility. however, zinc phosphate cement can irritate nerve pulp hence pulp protection is required but the use of polycarboxylate cement (zinc polycarboxylate, glass ionomer) is highly recommended since it is a more biologically compatible cement. known contraindications of dental cements dental materials such as filling and orthodontic instruments must satisfy biocompatibility requirements as they will be in the oral cavity for a long period of time. some dental cements can contain chemicals that may induce allergic reactions on various tissues in the oral cavity. common allergic reactions include stomatitis/dermatitis, urticaria, swelling, rash and rhinorrhea. these may predispose to life-threatening conditions such as anaphylaxis, oedema and cardiac arrhythmias. eugenol is widely used in dentistry for different applications including impression pastes, periodontal dressings, cements, filling materials, endodontic sealers and dry socket dressings. zinc oxide eugenol is a cement commonly used for provisional restorations and root canal obturation. although classified as non-cariogenic by the food and drug administration, eugenol is proven to be cytotoxic with the risk of anaphylactic reactions in certain patients. zinc oxide eugenol constituents a mixture of zinc oxide and eugenol to form a polymerised eugenol cement. the setting reaction produces an end product called zinc eugenolate which readily hydrolyses producing free eugenol that causes adverse effects on fibroblast and osteoclast-like cells. at high concentrations localised necrosis and reduced healing occurs whereas for low concentrations contact dermatitis is the common clinical manifestation. allergy contact dermatitis has been proven to be the highest clinical occurrence usually localised to soft tissues with buccal mucosa being the most prevalent. normally a patch test done by dermatologists will be used to diagnose the condition. glass ionomer cements have been used to substitute zinc oxide eugenol cements (thus removing the allergen), with positive outcome from patients.