1)Dental Cements.pdf

Dental Cements- I Asst. Prof. Dr. Melek ÇAM Istanbul Okan University Faculty of Dentistry Department of Restorative Dentistry ✤ Resistance to solubility at oral cavity ✤ Bonding ✤ Compressive and tensile strength ✤ Biocompatibility ✤ Working time ✤ Protect pulp from mechanic and electrical stimulus...

Dental Cements- I Asst. Prof. Dr. Melek ÇAM Istanbul Okan University Faculty of Dentistry Department of Restorative Dentistry ✤ Resistance to solubility at oral cavity ✤ Bonding ✤ Compressive and tensile strength ✤ Biocompatibility ✤ Working time ✤ Protect pulp from mechanic and electrical stimulus ✤ Temporary restoration ✤ Permanent restoration ✤ Temporary luting ✤ Permanent luting ✤ Root canal sealing ✤ Pulp protection Conventional cement Resin-based cement Zinc phosphate cement Zinc oxide eugenol cement Resin cement Polycarboxylate cement Resin modified glass Glass ionomer cement ionomer cement Classification ✤ Permanent luting cements ✤ Temporary luting cements ✤ Permanent restorative material ✤ Temporary restorative material ✤ Bases: Under amalgam / composite / gold, ✤ Pulp capping: Indirect pulp capping/ Direct pulp capping ✤ Cavity liners: Under amalgam / Composite Permanent luting Zinc phosphate cement Zinc polycarboxylate cement, Modified ZOE type-II Glass ionomer cement Under amalgam restorations Zinc phosphate cement Zinc polycarboxylate cement Reinforced ZOE GIC Type III Ca(OH)2 Pulp capping Ca(OH)2 ZOE Under composite restorations Zinc polycarboxylate cement Glass ionomer Type III Ca(OH)2 Cavity liner Ca(OH)2 Glass ionomer Type III Varnishes Properties ✤ Contents ✤ Compressice strength ✤ Elasticity modulus ✤ Film thickness ✤ Solubility ✤ Biocompatibility Zinc Phoshphate ✤ ✤ First introduced in 1878 and still used today One of the oldest and most widely used cements, ✤ Type I: Used for cementation; film thickness < 25 microns. ✤ ✤ Type II: Used as a base and for luting; film thickness 25-40 microns. Zinc Phosphate Powder 90.2% ZnO 8.2% MgO 1.4% SiO2 0.1% Bi2O3 0.1% BaO,Ba2SO4, CaO pH control Acid-base reaction rate Liquid Sintere d 1000C 38.2% Phosphoric acid 36% water 16.2% Aluminium or zinc phosphate 7.1% Zn 2.5%Al Setting reaction Zinc oxide Phosphoric acid Exotermic reaction Manipulation ✤ Glass slab ✤ Dry ✤ Lower temperature longer working time Water in liquid bottle evaporation !! Liquid / Powder Mixing rate Particule dimension Heat Humidity ✤ Working time~ 5 min ✤ Setting time ~ 2.5-8 min Mechanical Properties ✤ 75% of its ultimate strength within 1 hour. ✤ Compressive strength of cement is 104 Mpa ✤ Tensile strength - 5.5 Mpa ✤ Modulus of Elasticity is 13.7 gigapascals. ✤ Retention of cement is by mechanical interlocking Biocompatibility ✤ Phosphoric acid ✤ Liquid pH 2.0 ✤ 2 min. after mixing the pH is almost 2 and ✤ After 48 h the pH is 5.5. acidity, irritation Clinical Uses ✤ Base ✤ Temporary restoration ✤ Cementation Advantages Long record of clinical acceptability High compressive strength Thin film thickness. Disadvantages Low initial pH Lack of an adhesion to tooth structure Lack of anticariogenic effect Soluble in water. Zinc Polycarboxylate Cement ✤ introduced in the 1960s ✤ chelation reaction ✤ sets by an acid-base reaction between a powder and a liquid ✤ the carboxyl groups of the cement + calcium present in the tooth structure. Zinc Polycarboxylate Cement Liquid Powder polyacrylic acid. similar to that of zinc phosphate Or copolymer of acrylic acid (itakonic acid) Setting reaction Acid-base reaction Solve powder particule by acid Zn Mg Sn zinc polycarboxylate cross-link matrix Manipulation ✤ powder/liquid: 1.5 / 1 ✤ Glass slab/ mixing pad ✤ Loss water ! ✤ Shiny surface at mix cement ✤ Working time~ 2.5 dk ✤ Setting time ~ 6-9 dk ✤ Lowering the temperature increases working time ✤ The rubbery stage which makes it difficult to remove the cement. Bond to tooth structure ✤ Conditioning ✤ Polyacrylic acid react with Ca ✤ Chemical bond Polyacrilic acid Mechanical Properties ✤ Compressive strength 55-67 MPa ✤ Tensile strength 2.4-4.4 MPa ✤ Low solubility ✤ pH < 4.5 solubility increases Biocompatibility ✤ pH of the liquid = 1.7 , increases rapidly after mixing ✤ excellent biocompatibility with the pulp ✤ The size of polyacrylic acid molecule is bigger; less to disperse into the dentinal tubules ✤ pH of the cement rises more rapidly when compared to that of zinc phosphate. Clinical use ✤ Base ✤ Temporary restorations ✤ Cement crowns, stainless steel crown Advantages Disadvantages Adhesion Rapid rise in pH upon cementation Lack of penetration into the dentinal tubules Short working time Not resist plastic deformation Zinc oxide eugenol cement ✤ 1890s, one of the oldest used cement ✤ Less soluble in oral fluids ✤ Better marginal seal than zinc phosphate ✤ Powder and liquid ✤ Paste-paste system Powder 69% ZnO 29.3% white rosin (reduces brittleness) 1% zinc stearate (catalyst) 0.7% zinc asetate (accelerator) Liquid 85% Eugenol (reactor) 15% olive oil (plasticizer) Setting reaction ZnO + H2O Zn (OH)2 Zn(OH)2 + 2HE ZnE2 + 2H2O Water is needed for the reaction Manipulation For smoothening, clean up and hardening of the restoration, use a wet cotton pellet. Biocompatibility ✤ Sedative effect ✤ much less irritant to the pulp ✤ Antibacterial ✤ pH= 7 Clinical use ✤ Temporary cementation ✤ Temporary restoration ✤ Deep cavity preparation Advantages Disadvantages High soluble Soothing effect on the pulp Low strength Good short-term sealing. Long setting time Low compressive strength Zinc oxide eugenol cement ✤ not used as base material especially when unfilled and filled resins; eugenol interferes with polymerization process of resins. ✤ Composite restoration X ✤ Amalgam restoration + EBA (Ortho-ethoxybenzoic acid) Powder ZnO 70% Alumina 20-30% Fused quartz ve calcium Liquid Ortho-ethoxybenzoic acid (EBA) 62.5% Eugenol 37.5% EBA chelates with zinc forming zinc benzoate Addition of fused quartz, alumina and dicalcium phosphate has also shown to improve mechanical properties of cement EBA ✤ Increase in compressive and tensile strength. ✤ More powder can be incorporated to achieve standard consistency. ✤ Decrease in setting time (if concentration is < 70%). ✤ EBA does not show adverse effects on pulp. ✤ Temporary and long-term luting, temporary restoration, base and intermediate Advantage Easily mixed Decrease in setting time Lenger working time EBA pulp adverse effect (-) Disadvantage Plastic deformation Retention< zinc phosphate More powder in powder/liquid ratio Solubility in acidic environment Polymer Reinforced Zinc Oxide Powder ZnO % 80 Polymethyl methacrylate 20% — Increases strength Zinc stearate, zinc acetate Liquid Eugenol 85% Acetic acid 15% —Accelerator Resin helps; improving strength, smoothness of the mix and decreasing flow, solubility and brittleness of the cement. #17 and #47 Class I cavities