Cement 2
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The document discusses different types of dental cements including zinc phosphate cement, zinc polycarboxylate cement, glass ionomer cement, resin modified glass ionomer cement, metal reinforced glass ionomer cement, and resin cements. It describes the composition, setting reactions, properties, advantages, and disadvantages of each cement type. The document provides details on mixing and manipulating procedures for different cements.
Cement 2
- 1. الرح الرمحن هللا سمبمي
- 3. Uses •Cementation of fixed restorations •Cavity base under metallic filing to protect the pulp from thermal or electrical stimuli. •Temporary filing.
- 4. Composition Powder ZnO (90%): main ingredient. MgO (10%): aid in sintering by reduction of sintering temperature. SiO2: filler. Bi2O3: impart smoothness to the freshly mixed cement.
- 5. Liquid H3PO4 (50%): main ingredient. H2O (45%): it controls acid ionization Al2(PO4) 3 and ZnPO4:- They reduce the reaction rate ( retarder) They stabilize the pH of the acid.
- 6. Setting reaction of Zinc phosphate cement
- 7. Manipulation Powder/ liquid ratio. Mix on thick walled and cool glass slab + stainless steel spatula. To achieve slow neutralization of the liquid and allow heat dissipation. Mix over a large area. Mix the cements in increments: Add the small amount of powder into the liquid.
- 8. Mixing procedure There are three steps First add the small amount of powder into the liquid •To achieve the slow neutralization of the liquid. •To control the reaction.
- 9. Second Larger amount of powder is added to liquid •For further saturation of liquid to newly form zinc phosphate. •This step may not effect by heat released from the reaction.{because of the less amount of unreacted acid} Finally the small amount of powder is added again •To control the optimum consistency
- 10. Properties of Zinc phosphate cement I) It is the standard against which to compare newer cements due to •The long persistence of them in clinical performance. •Their manipulation is easy. •They have ideal rheological properties (set sharply to a relatively strong mass from a fluid consistency) .
- 11. II) Working time and setting time Working time commonly is 2-6 minute Setting time is 2.5-8 minute How to extend the setting time? Reducing powder/ liquid ratio {not recommended} Mixing on the cool glass slap {no moisture} Mixing over a large area. Mixing cements in increments.
- 12. Control of setting time at chair side (by operator) 1. Powder/liquid ratio Reducing P/L ratio will increase working and setting times. Drawbacks of this method: •physico-mechanical properties. •Lower initial pH (high acidity)
- 13. 2. Rate of powder incorporation Add small quantity of powder into the liquid for the first few increments to reduce the amount of heat generated and permits more powder to be incorporated into mix. This method prolong the working time without jeopardizing the physico-mechanical properties, therefore it is a recommended method .
- 14. 3. Spatulation time Increasing spatulation time, prolong the working and setting times. Prolonging spatulation time effectively destroys the matrix that was formed; that is, extra time is needed to rebuild the bulk of the matrix. 4. Temperature of the mixing slab It is the most effective method. Cooling the slab markedly retard the chemical reaction between the powder and the liquid so matrix formation is retarded. This permits incorporation of optimum amount of powder into the liquid without the mix developing an unduly high viscosity.
- 15. III) Viscosity It has low initial viscosity giving it these advantages:- •Easy flow during restoration seating. •Give low film thickness. •Its viscosity increase rapidly with time, therefore the restoration should be cemented rapidly after completing mixing to make use of the lower initial viscosity.
- 16. IV) Mechanical properties High compressive strength that allows amalgam condensation. In 10 minutes it attains 50% of its final strength which is attained after 24 hours. It has low tensile strength (brittle). Its E is similar to that of dentine. So it can support the overlying restoration and occlusal stresses.
- 17. V) Solubility •It is an important property especially when used for luting. Dissolution contributes to the marginal leakage around restorations and result in looseness of restorations or caries recurrence. They have high solubility rate especially thin mixes. Once they set, their solubility decreases, therefore they must be kept unexposed to oral fluid during their setting. VI) Biocompatibility Irritant (pH is 2 and reach neutrality after 24 hours) so in deep cavities, chemical insulator is needed.
- 18. Advantages 1. Speed and ease of usage. 2. Sufficient flow to form a thin layer for cementing of closely adapted crowns, fixed partial dentures and inlays. 3. Low thermal conductivity beneath a metallic restoration. 4. High compressive strength that allows amalgam condensation. Disadvantages 1. Solubility in mouth fluids. 2. Opaque material not suitable for visible surfaces.
- 19. Zinc polycarboxylate cement (ZPC)
- 20. The first cements that bond chemically to tooth structures. They combine the strength properties of Zn PO4 + biological acceptability of ZnOE. These materials have gone through several stages of development since their inception and progress is continuing.
- 21. Uses 1. Cementation of cast alloy, porcelain restorations and orthodontic bands. 2. Cavity liners or base materials. 3. Temporary filling material.
- 22. Forms • Conventional type: powder and liquid in two separate bottles. •Water settable (anhydrous) type: Its powder is the same like that of conventional type + freeze-dried powder of the polyacid in one bottle. Its liquid is either distilled water or weak solution of NaH2PO4.
- 23. Composition Powder Their composition and manufacturing are similar to those of zinc phosphate cement. Liquid •30-40% aqueous solution of Polyacrylic acid or acrylic acid copolymer. •Other organic acids such as:- Itaconic acid to prevent gelation during storage. Tartaric acid to control setting reaction. •NaH2PO4 which viscosity of polyacid and S.T.
- 24. Setting reaction The setting reaction is the same, whether the polyacid is freeze-dried and subsequently mixed with water, or if the conventional aqueous solution of the polyacid is used as liquid.
- 25. Properties Working and setting times It has shorter working time than zinc phosphate . Lowering the temperature of glass slab increase the working time. Cooling the powder only will retard the reaction without thickening the liquid. Mechanical properties Its compressive strength < zinc phosphate. Tensile strength > phosphate cement Solubility: It has low solubility in water.
- 26. Bonding to tooth structure •Bonds chemically to E & D. •The polycarboxylic acid reacts via COOH groups with calcium of hydroxyapatite forming chemical bonding .
- 27. •Bonding to enamel is higher than to dentine, probably because of the greater inorganic content and its greater homogeneity from a morphologic standpoint. •Smear layer removal by conditioning tooth surface with 10% polyacrylic acid for 10 seconds, will increase the bond strength. •It sticks to clean stainless steel.
- 28. Biocompatibility •The effect of polycarboxylate cements on the pulp is comparable to or less than that of zinc oxide-eugenol. •pH of polycarboxylate cement (1.7) is higher than that of a zinc phosphate cement (2) but polycarboxylate cement is more compatible due to :- •The rapid rise of the cement pH toward neutrality (few minutes for ZPC but 24 hours for ZNPO4. •Has bigger molecular size that block dentinal tubules.
- 29. Anticariogenicity The fluoride containing cements release fluoride, which is taken up by the neighboring enamel, thus increasing its resistance against caries.
- 30. Mechanism of action of fluoride in caries fitting •Fluoride inhibits the enzymes responsible for carbohydrates fermentation. •Fluoride shifts the equilibrium balance between demineralization and remineralization toward remineralization. •Fluorides act as a catalyst for uptake of calcium and phosphate ions.
- 31. Glass-ionomer cements (GICs) Uses •Restoration of erosion lesions •Luting agent for crown and bridge Types of GICs •Conventional GICs. •Metal reinforced GICs. •Resin modified GICs.
- 32. Conventional GIC Composition Powder Calcium aluminosilicate glass:- •Silica (SiO2) •Alumina (Al2O3) •Calcium fluoride (CaF2) and NaF.
- 33. Function of the glass powder •Releasing ions responsible for setting and properties of hard cement. •Contributes to aesthetics. Liquid is a Copolymer of •Acrylic acid: main reactant. •Itaconic acid: decrease viscosity of the liquid and inhibit gelation caused by intermolecular hydrogen bonding. •Tartaric acid: important hardener& controls pH during setting process.
- 34. Forms •Powder/liquid form (conventional). •Anhydrous cements (water settable). •Capsules: pre-proportioned so achieve the correct p/l ratio.
- 35. It occurs in three steps: Dissolution Gelation and hardening hydration
- 37. Properties of GICS Working and setting times •It is less than that of ZnPO4. •Water settable systems have longer working time and slower initial set than the hydrous systems. Mechanical properties •Compressive strength: comparable to that of ZnPO4 cement. •Tensile strength: slightly higher than that of ZnPO4 cement but still very low (brittle behavior). Modulus of elasticity: less than that of ZnPO4 cement, i.e. less rigid and more prone to elastic deformation.
- 38. Film thickness Similar to or less than that of ZoPO4 cement (25 μm or less). Solubility Good resistance to dissolution under oral conditions and improved by varnish protection. Bonding The same as Zinc polycarboxylate cement. Anticariogenic properties GICs possess anticariogenic properties as a result of fluoride release
- 39. Biocompatibility GICs are as compatible as zinc polycarboxylate cements for the same reasons discussed before with polycarboxylate. Aesthetics 1. GICs are considered inferior to many composite resins in aesthetic appearance. 2. GICs appeared dull and lifeless, and this limited their application to the restoration of erosion lesions and non-critical class III cavities. 3. In facts, the translucency of the GICs was more closely matched to that of dentine than that of enamel.
- 40. Advantages of GICs • Chemical bonding to tooth structures. •Biocompatible. •Long term fluoride release. •Good compressive strength. •Low solubility in oral fluids
- 41. Disadvantages of GICs •Technique sensitive as they are very sensitive to either water contamination or dehydration •Low abrasion resistance. •Short working time and long setting time. •Brittleness (low tensile strength) and low fracture toughness.
- 42. Resin modified glass ionomer cements (Hybrid GICs) The aim: is to overcome some of the drawbacks of the conventional GICs that result from the slow acid base reaction such as:- 1. Short working time and long setting time. 2. Cracking on desiccation and moisture sensitivity. 3. Poor resistance to acid attack.
- 43. Composition These products are hybrid of the two groups of materials, namely composite resin and GIC. Liquid •Methacrylate resin which enables setting to occur by polymerization. •Polyacid & ion-leachable glass to bring about setting by an acid-base mechanism. •HEMA: a hydrophilic methacrylate which enables both resin and acid components to co-exist in aqueous solution, the HEMA also takes part in the polymerization. •Water acid ionization enabling the acid-base reaction to occur.
- 44. Setting reaction of the Hybrid GICs •The acid-base reaction Free radical polymerization
- 45. Properties of resin modified GICs cement •Release of fluoride. •Ability to bind chemically to tooth structures. •A prolonged working time and a rapid setting time. •High strength. •Higher resistance to desiccation and acid attack.
- 46. Metal reinforced glass ionomer cements The aim of reinforcing the cement with metal is •To overcome the drawbacks of conventional GICs which are: Brittleness Low abrasion resistance Low fracture toughness •To enable using them as posterior filling materials.
- 47. Methods of metal reinforcements Silver alloy admix: It is performed by simply mixing of silver amalgam alloy powder to the conventional GIC (hand mix material). Cermet cement by sintering the silver only to the cement powder. Uses of metal reinforced GICs •Core build up material. Posterior filling material for deciduous teeth
- 48. Disadvantages of metal reinforced GICs •Reduction in fluoride release. •Reduction in bond strength with tooth structures. Advantages of metal reinforced GICs •Increase in abrasion resistance. •Little increase in compressive strength. •Reduction in solubility.
- 49. Resin Cements History Introduced 1950’s as an unfilled resin Current resin cements, introduced in late 1980’s Problems of Resin •High polymerization shrinkage. •High thermal expansion. •Lead to high microleakage.
- 50. Classification of Resin Cement (RC) According to filler content •Unfilled or filled (inorganic/glass filler particles) •Resin cement vs Resin composite cement According to polymerization reactions •Light-activated (Light-cure); •Chemical-activated (Chemical-, Self-cure); •Dual-activated (Dual-cure)
- 51. According to use of dentin bond agent (DBA) •Some resin cements do not require DBA, bonds directly to tooth (Adhesive RC). •Resin cements require DBA applied prior to the RC; DBA bonds to tooth, resin cement bonds to DBA (non-adhesive RC)
- 52. 4-META/MMA-TBB resin cement product 4-META/MMA-TBB resin cement (unfilled) Chemical-activation Composition: Base: 4-META/MMA (4-methyloxy ethyl trimellitic anhydride/ Methylmethacrylate) Catalyst: TBB (tributyl boron oxide) Powder: Polymethylmethacrylate powder (NO glass filler particles)
- 53. Manipulation •Etch, rinse, and dry •Mix Base + Catalyst , Apply 1st mix to tooth •Add 2 scoops powder (PMMA) to 2nd mix of Base/Catalyst •Apply 2nd mix to restoration •Seat restoration Application: metal-based restorations
- 54. Advantages •Direct bond to tooth, No DBA •Medium-high strength bond (~17 MPa) Disadvantages •Bond strength NOT long-term: ~10 MPa at 1 year. •Higher solubility-- related to decreased bond strength.
- 55. Resin Composite Cements Basic description • Bis-GMA based resin (Bis-type methacrylate/TEGDMA resin ) • Filler: Silanated glass, silica particles • Polymerization activation: Light, Chemical, Dual • 10 MDP: Phosphate ester, Adhesive monomer for tooth structure. • Brand dependent use of DBA Ex: Resin Composite Cement: Panavia 21 (Available at UMKC) • Chemical-activation .
- 56. Manipulation • Etch and prime tooth structure with self-etch ED primer • Apply for 60 sec, then dry. Do not rinse. • Acidic HEMA primer: pH ~2-3; Do not use conventional phosphoric acid etch • Mix catalyst & base pastes, 20 sec (Spread thin on pad, prevent premature set) • Apply to restoration, seat restoration • Clean excess cement using; microbrushes, gauze. Floss between teeth to remove inter-proximal excess.