Dental cement • Substance that hardens to act as a base, liner, filling material, or adhesive to bind devices & prosthesis to the tooth structure or to each other. • Supplied as 2 component system, powder (base) & a liquid (acid) • Liquids are acids (proton donors) & powder are basic (alkaline) in nature .
Acid base reaction :- • Reaction between powder & liquid is essentially is an acid base reaction • Chemical reaction between a compound with replaceable hydrogen ion (acid) & a substance with replaceable hydroxide ion (base) that yields water & a salt for aqueous cements.
Uses of dental cements For, • Pulpal protection (liners, bases, varnishes) • Luting/ cementation (crowns, inlays, onlays veneers) • Restorations (temporary and permanent) • Surgical dressing (e.g. periodontal surgery)
Luting agent • Word LUTE means to hold or retain indirect restoration (crowns, bridges and other devices)in a fixed position with in the mouth
Luting agent • Are a viscous material placed between tooth structure & a prosthesis that hardens through a chemical reaction to firmly attach the prosthesis to the tooth structure • Dental luting agent applied as a thin layer (<25 µm) to provide a link between a fixed prosthesis & the prepared tooth
Luting consistency :- • Luting cement is mixed to a consistency called primary consistency / luting consistency or thread like consistency • Means on lifting the spatula, cement forms a thin strand about an inch ,if this point is further extended ,the mix slowly springs back into the mix
LUTING (Cementation) Cementation is the process by which crowns, bridges and other devices are fixed or attached to tooth structure using an intermediate material called dental cement.
Types • Temporary cementation • Permanent cementation
Temporary Cementation • Should have some soothing effect (Obtundent) on the pulp. • Temporary cementing agents are used for trial of the appliance for few days for approval by the patient • Have low strength < 75 Mpa for easy removal • E.g. :- Zinc oxide eugenol (type – 1), calcium hydroxide
Permanent Cementation • Have higher strength > 75Mpa • Thin film thickness <25 microns • Insoluble in oral fluids & must be strong • Chemical bonding to the tooth structure & metal appliances • Should be fluid enough to flow (Low consistency)
Ex. Modified ZnOE , ZnPO4, GIC type1, resin cement, Polycarboxylate cement ,zinc silico phosphate cement
Ideal requirements of dental cements • Luting • Restorative
Ideal requirement of luting cement • Film thickness :- should be low. According to ADA specification no 96 for water -based cement, film thickness should be <25 µm • Viscosity :- should have low initial viscosity, to allow flow of the cement properly ,so that proper seating occurs • Retention :- by chemical or mechanical or combination of both
Should have high strength • Good fracture toughness to resist, stresses at restorative tooth interface • Solubility :- should be low in oral fluids ic dissolution or erosion may lead to failure by loss of retention or by the initiation of caries • Adequate W.T for mixing ,for loading & for seating restoration in mouth ,followed by shorter S.T
Have good esthetic especially for cementation of translucent material such as ceramics • Low thermal conductivity or diffusivity . since many of the restorations cemented are metals or alloys • Easy to manipulate • Biocompatible
Ideal requirement of restorative cement 1.Biological properties :- • Should be biocompatible with the pulp – non toxic & non irritant • Bacteriostatic –resist the growth of bacteria or micro organisms • Cariostatic & anticariogenic • Obtundent & promote healing
2. Chemical properties :- • Resist large variation in PH& should not under go disintegration/dissolution • Chemically inert & should not absorb saliva or other fluids • Metallic restoration should not under go tarnish & corrosion • Metallic restoration should not produce galvanic current
Chemically bond with the tooth structure which minimizes penetration of fluids & bacteria at the margins , so that secondary caries & pulpal injury is reduced
3. Rheological properties :- • Good flow , constant low viscosity during manipulation • Longer W.T for easy placement , manipulation of the materials ,followed by Shorter S.T is comfortable & convenient for both clinician & patient – command set properties • Shear thinning & pseudoplastic property (viscosity decreases at higher shearing stresses )to assist proper cementation • Film thickness < 25um for luting & 25-40 um for bases
4. Mechanical properties :- • Should be adequate to withstand forces of mastication • These requirement also depend upon the types & position of the restoration like – anterior ,posterior & class I to v cavities .
Good A.R & surface hardness same as that of tooth enamel ~ 340 KHN , So that softer restoration will not get abraded or harder restoration ( like -ceramic ) will not abrade the opposing tooth • High PL & elastic limitor yield strength to resist any permanent deformation
High stiffness or MOE to resist any dimensional change. Ideally MOE should be similar to that of dentin (14,000-18,000 Mpa) • Larger compressive strength to resist fracture from larger dynamic masticating forces • Temporary restoration - < 35 Mpa ( less for easy removal) • Intermediate restoration – 35-100 Mpa • Permanent restoration - > 300 Mpa
High fatigue strength & endurance limit for longer service • Good bond strength (chemical bonding) to prevent marginal leakage & this minimizes the less removal of tooth material during cavity preparation (GIC)
5. Thermal properties:- • Should not undergo expansion & contraction during thermal change ( due to hot & cold food). So COTE should be similar to that of enamel & dentin nearly 11.4 ppm/*c to minimize micro leakage during thermal changes .
Should be thermal insulator ,to protect the pulp from harmful effects of hot & cold stimuli. However most of the metallic restoration DFG, silver amalgam, HN,N,PBM alloy castings are good conductor of heat & electricity. So requires thermal insulating base
6. Aesthetic requirement :- Are the prime importance for the anterior restoration • Transparent or translucent & ability to incorporate any desired shade or opacifiers • Same refractive index as tooth • Hue ,value , chroma same as that of tooth for correct color matching • Color parameter should not change or undergo discoloration
7 . Other requirement :- • Should be radio-opaque for easy detection of secondary caries • Easy to manipulate • Longer shelf life, easily available
Classification of restorative material • 1. According to nature of material 1. Metallic restoratives :- - Indirect casting – HN,N,PBM alloys - Direct filing material – direct filling gold ( DFG), silver amalgam 2. Non - metallic restoratives:- - Ceramic (PJC , veneers , inlays ) - Composite resins - Dental cement - Metal ceramic
2. According to lifespan • Temporary restoratives – E.g.- ZnOE- type III , Calcium hydroxide ,acrylic crown • Intermediate restoratives – E.g.- zinc phosphate cement, resin bonded ZnoE ,zinc polycarboxylate, GIC, Zinc silico-phosphate cement, acrylic crown & bridges • Permanent restoratives - E.g. – Amalgam , posterior composite, indirect restorations ( gold inlays, crowns) , DFG ,HN,N,PBM alloy casting , modified GIC, ceramic
3. According to the placement :- • Anterior restoratives :- Ceramic , GIC, composite resin, metal ceramic • Posterior restoratives :- Amalgam , hybrid composite , DFG ,HN,N,PBM alloy casting , modified GIC, metal ceramic
4 . According to the method of hardening • Acid base reaction – ZnoE, ZnPo4, zinc polycarboxylate, GIC • Polymerization reaction – Composite resin, acrylics, compomers
According to the Applications • Metallic Restorations – Obtained by casting • Inlays , crowns FPD (crown & bridges),RPD ,Pontics, abutments ,DFG , Silver amalgam • Nonmetallic restorations • Pulp protecting agents • Cement bases ,cavity primers , liners & varnishes • Cementing or luting material • Tooth filling materials • Root canal sealants • Pit & fissure sealants
1.According to their function :- FunctionsMaterial used 1.Pulp capping Calcium hydroxide Ca(OH)2, ZnOE 2. Low strength base Calcium hydroxide, ZnOE 3. High strength base Modified ZnOE,ZnPO4, GIC (type -3), Ca(OH)2, Zinc Polycarboxylate 4.Temporary cementation ZnOE, Ca(OH)2 5.Permanent cementation Modified ZnOE,GIC( Type -1), Zinc Polycarboxylate , ZnPO4, ZnSiPO4
6. Temporary restoration Modified ZnOE, ZnOE ,zinc polycarboxylate 7. Intermediate Zinc polycarboxylate , ZnSiPO4 , restoration alumina modified ZnOE, ZnPO4 8. Cavity liners GIC (type3), Ca(OH)2, zinc polycarboxylate 9. Cavity varnish Gum or resins in organic solvent 10. Pit & fissure sealants GIC (type 4) 11. Cementation of zinc polycarboxylate , ZnPO4 orthodontic bands 12. Root canal sealants ZnOE ,gutta percha ,zinc polycarboxylate
2. According to the application Material primary secondary applicationapplication 1. ZnOE I Temp. cementation Root canal sealing, pulp capping ZnOE II Permanent cementation Periodontic bandage ZnOE III Temporary restoration, Base Pulp capping ZnOE IV Cavity Liner surgical dressing 2. Ca(OH) 2 Pulp capping Weak cement base, Cavity liner
3. ZnPO4 Luting metallic restoration Thermal insulating & base, intermediate orthodontic bands restoration 4. Zinc Polycarboxylate Luting, base cementation of orthodontic bands Intermediate restoration, root canal sealants, linier 5. Silicate Anterior restoration Rampant caries of deciduous teeth 6. ZnSiPO4 Luting of porcelain crown Intermediate & veneers restoration, Luting of alloy fabrication, orthodontic bands
7. GIC I Luting GIC II Restoration Restoration of cervical erosion cavity GIC III Liner, Bases pit & fissure sealant , core build up GIC metal restoration modified Compomer posterior Luting restoration orthodontic bands
3.According to their SR & ingredients • Zinc oxide cements 1. ZnO + HE ZnOE cement 2. ZnO + EBA EBA cement 3. ZnO + H3PO4 ZnPO4 cement 4. ZnO + Polycarboxylic acid Zinc polycarboxylate cement
Aluminosilicate glass cement 1.(sio2+ Al2o3) + H3PO4 Silicate cement 2. (sio2+ Al2o3) + poly carboxylic acid GIC 3. (sio2+ Al2o3) + resin Compomer 4. (sio2+ Al2o3) + metal Modified GIC • Combination ZnO + (sio2+ Al2o3) + H3PO4 ZnSiPO4 ZnO + resin +HE Resin bonded ZnOE • Calcium hydroxide cement
4. According to the PH value • Acidic cement ( PH< 7)- silicate cement, zinc silico phosphate cement, zinc phosphate cement, zinc polycarboxylate cement, GIC, compomer • Neutral cement ( PH = 6.6-7.3)- – ZnOE & its modifications • Alkaline cement ( PH > 7)- – calcium hydroxide (dycal).