dental material dental material dental products are specially fabricated materials, designed for use in dentistry. there are many different types of dental products, and their characteristics vary according to their intended purpose. this article is about types of dental restorative materials. for dental fillings, see dental restoration. temporary dressings a temporary dressing is a dental filling which is not intended to last in the long term. they are interim materials which may have therapeutic properties. a common use of temporary dressing occurs if root canal therapy is carried out over more than one appointment. in between each visit, the pulp canal system must be protected from contamination from the oral cavity, and a temporary filling is placed in the access cavity. examples include: zinc oxide eugenol—bactericidal, cheap and easy to remove. eugenol is derived from oil of cloves, and has an obtundant effect on the tooth and decreases toothache. it is suitable temporary material providing there are no biting forces on it. it is also contraindicated if the final restorative material is composite because eugenol adversely effects the bond/polymerization process, also, when applied directly on the pulp tissue, it can produce chronic inflammation and result in pulp necrosis. examples brands: kalzinol, sedanol. cements dental cements are used most often to bond indirect restorations such as crowns to the natural tooth surface. examples include: zinc oxide cement—self setting and harden when in contact with saliva. example brands: cavit, coltosol. zinc phosphate cement zinc polycarboxylate cement—adheres to enamel and dentin. example brands: polyf. glass ionomer cement resin-based cement copper-based cement impression materials main article: dental impression dental impressions are negative imprints of teeth and oral soft tissues from which a positive representation can be cast. they are used in prosthodontics (to make dentures), orthodontics, restorative dentistry, dental implantology and oral and maxillofacial surgery. : 136–137 rigidity- inelastic (rigid) impression materials are used with patients with shallow undercuts. elasticity- elastic impression materials are used in patients with deep undercuts as it must be flexible enough to reach the end-point of the undercut. these two properties are essential because patients have varying soft-tissue undercuts (shallow or deep undercuts). in order to obtain an accurate impression, a suitable property of impression material must be used. impression materials are designed to be liquid or semi-solid when first mixed, then set hard in a few minutes, leaving imprints of oral structures. common dental impression materials include: sodium alginate polyether silicones historically these products were used as impression materials: plaster of paris zinc oxide eugenol agar lining materials dental lining materials are used during restorations of large cavities, and are placed between the remaining tooth structure and the restoration material. the purpose of this is to protect the dentinal tubules and the sensitive pulp, forming a barrier-like structure. after drilling the caries out of the tooth, the dentist applies a thin layer (approximately 1/2mm) to the base of the tooth, followed by light curing. another layer might be applied if the cavity is very large and deep. there are many functions to dental lining materials, some of which are listed below: lining materials protect the weak tooth from post-operative hypersensitivity, reducing patient discomfort and allowing the tooth to heal at a faster rate after the procedure. some dental restorative materials such as acrylic monomers in resin-based materials and phosphoric acid in silicate materials may pose toxic and irritable effects to the pulp. lining materials protect the tooth from the aforementioned irritants. lining materials serve as an insulating layer to the tooth pulp from sudden changes in temperature when the patient takes hot or cold food, protecting it from potential pain resulting from thermal conductivity. additionally, lining materials are electrically insulating, preventing corrosion by galvanic cell in the event where two dissimilar metals (e.g.: gold or amalgam) are placed next to each other. type calcium hydroxide calcium hydroxide has a relatively low compressive strength and a viscous consistency making them difficult to apply to cavities in thick sections, a common technique used to overcome this issue would be to apply a thin sub-lining of a calcium hydroxide lining and then building up with zinc phosphate prior to amalgam condensation. generates a relatively high ph environment around area surrounding the cement due to calcium hydroxide leaking out thus making it bactericidal. it also has a unique effect of initiating calcification and stimulating the formation of secondary dentine due to an irritation effect of the pulp tissues by the cement. it is also radio-opaque and acts as a good thermal and electrical insulation. however, due to its low compressive strength it is unable to withstand amalgam packing thus a strong cement base material should be placed above it to counter this. calcium silicate-based liners have become alternatives to calcium hydroxide and a preferred material among practitioners for its bioactive and sealing properties; the material triggers a biological response and results in formation of bonding with the tissue. commonly used as pulp capping agents and lining materials for silicate and resin-based filling materials. calcium-silicate liner used as a pulp capping material it is usually supplied as 2 pastes, a glycol salicylate and another paste containing zinc oxide with calcium hydroxide. on mixing a chelate compounds are formed. light activated versions are also available which contains polymersation activators, hydroexyethyl methacrylate, dimethacrylate which when light activated will result in a light activated polymerization reaction of a modified methacrylate monomer. polycarboxylate cement polycarboxylate cement have decent compressive strength to resists amalgam condensation and are acidic but less acidic than phosphate cements due to it having a higher molecular weight and polyacrylic acid being a weaker acid than phosphoric acid. they also form a strong bond with dentine and enamel allowing it to form a coronal seal. in addition it is an electrical and thermal insulator while also releasing fluoride rendering it bacteriostatic, furthermore it being radio-opaque makes it an excellent lining material. care has to be taken in handling such material as it has a strong bond with stainless steel instruments once it sets. commonly used as luting agents or as cavity base materials, however they tend to be rubbery during its setting reaction and adhere to stainless steel instruments thus most operators would prefer not to use them in deep cavities. it is usually supplied as a power containing zinc oxide and a liquid containing aqueous polyacrylic acid. the reaction consists of an acid base reaction with zinc oxide reacting with the acid groups in polyacid to form a reaction product of unreacted zinc oxide cores bound by a salt matrix with polyacrylic acid chains cross linking with zinc ions. glass ionomer it has the strongest compressive and tensile strength out of all the linings, thus it can withstand amalgam condensation in high stress bearing areas such as class ii cavities. gi is used as a lining material as it is very compatible with most restorative materials, insulates thermally and electrically and adheres to enamel and dentine. lining gi contains glass of smaller particle sizes in comparison to its adhesive restorative mix to allow formation of a thinner film. some variations are also radiopaque which makes it good for x ray cavity detection. in addition, gi is bacteriostatic due to its fluoride release from un-reacted glass cores. gis are usually used as a lining material for composite resins or as luting agents for orthodontic bands. the reaction is an acid-base reaction between calcium-aluminum-silicate glass powder and polyacrylic acid. they come in a powder and liquid which are mixed on a pad or in capsules which are for single usage. the resin-modified gis contain a photo-initiator usually camphorquinone and an amide, and are light cured with a led light curing unit. setting takes place by a combination of acid-base reaction and chemically activated polymerization. zinc oxide eugenol zinc oxide eugenol has the lowest compressive and tensile strength in relative to the rest of the liners thus this lining should be limited to small or non stress bearing areas such as class v cavities. this cavity lining is often used with a high strength base to provide strength, rigidity and thermal insulation. zinc oxide eugenol can be used as linings in deep cavities without causing harm to the pulp, due to its obtundant effect on the pulp as well as its bactericidal properties due to zinc. however eugenol may have an effect on resin based filling materials as it interferes with the polymerization and occasionally causes discoloration, thus caution should be taken when using both in tandem. it is also radio-opaque allowing fillings to be visible by x-rays. zinc oxide eugenol is usually used as a temporary filling/luting agent due to its low compressive strength and thus easily removed or as a lining for amalgam as it is incompatible with composites resins. it is supplied as a two paste system. equal length of 2 pastes are dispensed into a paper pad and mixed. agent advantages disadvantages calcium hydroxide alkaline nature promotes anti-bacterial atmosphere therapeutic effect for dentinal tubules low thermal conductivity can provide thermal insulation radiopaque thermal and electrical insulator good restorative material compatibility soluble to oral fluids thus restricted to dentine coverage only viscous consistency making it difficult to apply to cavities in thick sections\ low compressive strength need a second layer of strong cement base above it polycarboxylate cement decent compressive and tensile strength radiopaque bacteriostatic due to fluoride release adhesive thus coronal seal compatible with most restorative materials thermal and electrical insulator mildly acidic thus a mild irritant hard to handle due to strong bond with stainless steel instruments rubbery during setting reaction thus hard to manipulate in deep cavities zinc oxide eugenol can be used as a temporary filling or lining as it is easy to remove even after set bactericidal due to zinc thermal and electrical insulator radiopaque due to zinc obtundant lowest compressive and tensile strength of all linings only can be used on areas with small or non stress incompatible with resin composites due to polymerization interference non adhesive thus no coronal seal glass ionomer relatively high compressive and tensile strength radiopaque very adhesive to enamel and dentine thus don't need a bonding agent bacteriosatic due to fluoride release adhesive thus coronal seal good compatibility with restorative materials thermal and electrical insulator mildly acidic thus a mild irritant remain acidic for some time after mixing not an obtundant restorative materials glass ionomer cement - composite resin spectrum of restorative materials used in dentistry. towards the gic end of the spectrum, there is increasing fluoride release and increasing acid-base content; towards the composite resin end of the spectrum, there is increasing light cure percentage and increased flexural strength. dental restorative materials are used to replace tooth structure loss, usually due to dental caries (dental cavities), but also tooth wear and dental trauma. on other occasions, such materials may be used for cosmetic purposes to alter the appearance of an individual's teeth. there are many challenges for the physical properties of the ideal dental restorative material. the goal of research and development in restorative materials is to develop the ideal restorative material. the ideal restorative material would be identical to natural tooth structure in strength, adherence, and appearance. the properties of an ideal filling material can be divided into four categories: physical properties, biocompatibility, aesthetics and application. requisite physical properties include low thermal conductivity and expansion, resistance to different categories of forces and wear such as attrition and abrasion, and resistance to chemical erosion. there must also be good bonding strength to the tooth. everyday masticatory forces and conditions must be withstood without material fatigue. root canal sealer used in endodontic therapybiocompatibility refers to how well the material coexists with the biological equilibrium of the tooth and body systems. since fillings are in close contact with mucosa, tooth, and pulp, biocompatibility is very important. common problems with some of the current dental materials include chemical leakage from the material, pulpal irritation and less commonly allergy. some of the byproducts of the chemical reactions during different stages of material hardening need to be considered. radiopacity in dental materials is an important property that allows for distinguishing restorations from teeth and surrounding structures, assessing the absorption of materials into bone structure, and detecting cement dissolution or other failures that could cause harm to the patient. cements, composites, endodontic sealers, bone grafts,