dental cement dental cement dental cements have a wide range of dental and orthodontic applications. common uses include temporary restoration of teeth, cavity linings to provide pulpal protection, sedation or insulation and cementing fixed prosthodontic appliances. recent uses of dental cement also include two-photon calcium imaging of neuronal activity in brains of animal models in basic experimental neuroscience. traditional cements have separate powder and liquid components which are manually mixed to form a viscous liquid. the liquid sets to form a brittle solid after application on the treated surface. more advanced cements, such as gic, can come in capsules and are mechanically mixed using rotating or oscillating mixing machines. ideal cement properties non irritant – many cements are acidic and irritate the pulp. however, on setting there is a rapid increase in ph. polycarboxylate cement is considered the most biocompatible type due to having the most rapid ph rise. provide a good marginal seal to prevent marginal leakage. resistant to dissolution in saliva, or other oral fluid – a primary cause of cement failure is dissolution of the cement at the margins of a restoration. high strength in tension, shear and compression to resist stress at the restoration-tooth interface. adequate working and setting time. good aesthetics. good thermal and chemical resistance. opacity – for diagnostic purposes on radiographs. low film thickness (ideally 25 microns). retention – if an adhesive bond occurs between the cement and the restorative material, retention is greatly enhanced. otherwise, the retention depends on the geometry of the tooth preparation. comparison of cements cement type brands(manufacturer) indications contra-indications advantages disadvantages zinc phosphate hy-bond zinc phosphate cement (shofu dental) modern tenacin (l.d. caulk) zinc cement improved (mission white dental) long span bridges metal crowns metal-ceramic crowns feldspathic porcelain jacket crowns orthodontic bands cavity liner all-ceramic restorations – due to setting expansion inadequate retention form of tooth preparation highest elastic modulus high compressive strength low film thickness low cost acidic – possible pulpal irritation lack of antibacterial action brittle lack of adhesion low tensile strength provides only mechanical seal exothermic during set high solubility (in oral fluids) low hardness zinc polycarboxylate hy-bond polycarboxylate cement (shofu dental) tylok plus (l.d. caulk) durelon porcelain restorations orthodontic bands cavity liner metal crowns metal-ceramic crowns titanium based restorations (cement discolouration occurs) antibacterial low irritation adhesive to tooth structure sufficient compressive strength higher tensile strength than zinc phosphate low post-op sensitivity low ph initially low resistance to erosion in acidic environment short working time glass ionomer (gi) fuji i (gc america) ketac-cem (3m/espe) metal and metal-ceramic restorations porcelain restorations all ceramic crowns with high strength cores such as alumina or zirconia orthodontic bands cavity liners restoring erosion lesions allergy (rare) dentine close to pulp (place suitable liner first) adhere to teeth and metal fluoride release ease of mixing good flow cheap aesthetic thermal compatible with enamel low shrinkage good resistance to acid dissolution translucency ?? soluble in water rapid set – time limitation especially in cementation of several units. moisture sensitivity at set brittle inherent opacity low fracture toughness poor wear resistance radiolucency possible pulpal sensitivity resin modified glass ionomer (rmgi) fuji plus (gc america) vitremer luting (3m/espe) advance (l.d. caulk) rely x luting cavity liners core buildups luting cements crowns orthodontic appliances all-ceramic crowns – due to uptake of water causing swelling and pressure on the crown veneer – not retentive enough dual cure fluoride release higher flexural strength than gi capable of bonding to composite materials setting expansion may lead to cracking of all-ceramic crowns moisture sensitive zinc oxide eugenol (zoe) temp-bond fynal (l.d. caulk) super eba (bosworth) temporary crowns, bridges provisional cementation of fixed partial dentures provisional restoration of teeth cavity liner when resin cement to be used for permanent cementation neutral ph good sealing ability resistance to marginal penetration obtundent effect on pulpal tissues weakest of the cements low strength low abrasion resistance soluble (in oral fluids) little anticariogenic action resin cements panavia 21 (kurarary) multilink automix sg(vivadent) relyx unicem 2 (3m/espe) maxcem elite (kerr) theracem (bisco) all crown types bonding fixed partial dentures inlays veneers indirect resin restorations resin-fiber posts if a zoe cement has been used for the previous temporary. light cured under a metal crown since it would not cure through the metal. strongest of the cement – highest tensile strength. least soluble (in oral fluids) high micromechanical bonding to prepared enamel, dentin, alloys, and ceramic surfaces neutral ph setting shrinkage – contributing to marginal leakage difficult sealing requires a meticulous and critical technique possible pulpal sensitivity difficult to remove excess cement cements based on phosphoric acid types composition setting reaction disadvantages advantages applications zinc phosphate cements usually a powder (zinc oxide with other metallic oxides, e.g. magnesium oxide) and liquid (aqueous solution of phosphoric acid) zinc oxide or aluminium oxide buffer (up to 10%) mixed by hand 3zno + 2h3po4 +h2o →zn3(po4)2 4h2o may irritate dental pulp, especially when used in cavity lining. small amounts of fluoride salt, in the cement can leak out to provide protection to surrounding tooth substance non-opaque set material because of unconsumed zinc oxide widely used as lute applications silicophosphate cements (obsolete) supplied as a powder (zinc oxide and aluminosilicate glass mixture) and liquid (aqueous solution of phosphoric acid with buffers) forms unconsumed cores of zinc oxide and glass particles enclosed by matrix of zinc and aluminium phosphates. releases f− ions irritates dental pulp stronger and less soluble than phosphate cement aluminosilicate glass particles contain fluoride, anti-cariogenic for surrounding tooth substance mainly temporary filling materials not used anymore copper cements (obsolete) supplied as a powder (zinc oxide and black copper oxide) and liquid (aqueous solution of phosphoric acid) similar to zinc phosphate black color caused by copper poor durability bactericidal effect rarely used dental cements based on organometallic chelate compounds types composition setting reaction advantages disadvantages applications zinc oxide/eugenol cements supplied as two pastes or as a powder (zinc oxide) and liquid (zinc acetate, eugenol, olive oil) a slow chelation reaction of two eugenol molecules and one zinc ion to form zinc eugenolate without moisture. however, setting can be completed fast when water is present. bactericidal effect due to free eugenol pulpal damage due to production of exotoxins high solubility in water interfere with polymerisation process and leads to discoloration mainly used for lining under amalgam restorations ortho-ethoxybenzoic acid (eba) cements supplied as a powder (mainly zinc oxide and reinforcing agents: quartz and hydrogenated rosin) and liquid o-ethoxybenzoic acid and eugenol) similar to zinc oxide/eugenol materials higher powder/liquid ratio can be achieved, so the set material can be strong lower solubility than zinc oxide/eugenol products less retention than zinc phosphate cements luting cements primarily calcium hydroxide cements calcium hydroxide in water (water can be substitute by a solution of methyl cellulose in water or a synthetic polymer in volatile organic solvent) calcium hydroxide is usually supplied as two pastes chelate compounds are formed and chelation is largely due to zinc ions antibacterial properties induce formation of secondary dentine layer setting may be slow due to low viscosity exothermic setting reaction relatively low compressive strength used as lining material under silicate and resin-based filling materials dental applications dental cements can be utilised in a variety of ways depending on the composition and mixture of the material. the following categories outline the main uses of cements in dental procedures. temporary restorations unlike composite and amalgam restorations, cements are usually used as a temporary restorative material. this is generally due to their reduced mechanical properties which may not withstand long-term occlusal load. gic – glass ionomer cement zinc polycarboxylate cement zinc oxide eugenol cement rmgic "dentsply" cement bonded amalgam restorations amalgam does not bond to tooth tissue and therefore requires mechanical retention in the form of undercuts, slots and grooves. however, if insufficient tooth tissue remains after cavity preparation to provide such retentive features, a cement can be utilised to help retain the amalgam in the cavity. historically, zinc phosphate and polycarboxylate cements were used for this technique, however since the mid-1980s composite resins have been the material of choice due to their adhesive properties. common resin cements utilised for bonded amalgams are rmgic and dual-cure resin based composite. liners and pulp protection when a cavity reaches close proximity to the pulp chamber, it is advisable to protect the pulp from further insult by placing a base or liner as a means of insulation from the definitive restoration. cements indicated for liners and bases include: zinc oxide eugenol zinc polycaroxylate rmgic pulp capping is a method to protect the pulp chamber if the clinician suspects it may have been exposed by caries or cavity preparation. indirect pulp caps are indicated for suspected micro-exposures whereas direct pulp caps are place on a visibly exposed pulp. in order to encourage pulpal recovery, it is important to use a sedative, non-cytotoxic material such as setting calcium hydroxide cement. luting cements luting materials are used to cement fixed prosthodontics such as crowns and bridges. luting cements are often of similar composition to restorative cements, however they usually have less filler meaning the cement is less viscous. rmgic gic zinc polycarboxylate cement zinc oxide eugenol luting cement summary of clinical applications clinical application type of cement used crowns metal zinc phosphate, gi, rmgi, self or dual cured resin * metal ceramic zinc phosphate, gi, rmgi, self or dual cured resin * all ceramic resin cement temporary crown zinc oxide eugenol cement 3/4 crown zinc phosphate, gi, rmgi, self or dual cured resin * bridges conventional zinc phosphate, gi, rmgi, self or dual cured resin * resin bonded resin cement temporary bridge zinc oxide eugenol cement veneers resin cement inlay zinc phosphate, gi, rmgi, self or dual cured resin * onlay zinc phosphate, gi, rmgi, self or dual cured resin * post and core metal post any cement which is non-adhesive (not resin cements) fibre post resin cement orthodontic brackets resin cement orthodontic molar bands gi, zinc polycarboxylate, composite composition and classification iso classification cements are classified on the basis of their components. generally, they can be classified into categories: water-based acid-base cements: zinc phosphate (zn3(po4)2), zinc polyacrylate (polycarboxylate), glass ionomer (gic). these contain metal oxide or silicate fillers embedded in a salt matrix. non-aqueous/ oil bases acid-base cements: zinc oxide eugenol and non-eugenol zinc oxide. these contain metal oxide fillers embedded in a metal salt matrix. resin-based: acrylate or methacrylate resin cements, including the latest generation of self-adhesive resin cements that contain silicate or other types of fillers in an organic resin matrix. cements can be classified based on the type of their matrix: phosphate (zinc phosphate, silico phosphate) polycarboxylate (zinc polycarboxylate, glass ionomer) phenolate (zinc oxide–eugenol and eba) resin (polymeric) based on time of use: conventional (zinc phosphate, zinc polycarboxylate, zinc oxide eugenol, glass ionomer cement) contemporary (resin cements, resin modified glass ionomers). resin-based cements these cements are resin based composites. they are commonly used to definitively cement indirect restorations, especially resin bonded bridges and ceramic or indirect composite restorations, to the tooth tissue. they are usually used in conjunction with a bonding agent as they have no ability to bond to the tooth, although there are some products that can be applied directly to the tooth (self-etching products). panavia was created in tamil nadu, india. the name panavia in hindi sanskrit means "stick to a tooth". it is described to be one of the toughest cements in the world. there are 3 main resin based cements; light-cured – required a curing lamp to complete set dual-cured – can be light cured at the restoration margins but chemically cure in areas that the curing lamp cannot penetrate self-etch – these etch the tooth surface and do not require an intermediate bonding agent resin cements come in a range of shades to improve aesthetics. mechanical properties fracture toughness thermocycling significantly reduces the fracture toughness of all resin-based cements except relyx unicem 2 and g-cem linkace. compressive strength all automixed resin-based cements have greater compressive strength than hand-mixed counterpart, except for variolink ii. zinc polycarboxylate cements zinc polycarboxylate was invented in 1968 and was revolutionary as it was the first cement to exhibit the ability to chemically bond to the tooth surface. very little pulpal irritation is seen with its use due to the large size of the polyacrylic acid molecule. this cement is commonly used for the