dental cements (3) dental material


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dental cements (3) dental material

  1. 1. ACID-BASE REACTION CEMENTSACID-BASE REACTION CEMENTS II. Cements based on phosphoric acidII. Cements based on phosphoric acid A.A. Zinc phosphate cementZinc phosphate cement B.B. Silicate cementSilicate cement C.C. Silicophosphate cementSilicophosphate cement
  2. 2. II. Cements based on phosphoric acidII. Cements based on phosphoric acid Zinc oxide Fluro-alumino- silicate glass Phosphoric acid Silicate cementZinc-phosphate cement Silico-phosphate cement
  3. 3. A. ZINC-PHOSPHATE CEMENTA. ZINC-PHOSPHATE CEMENT Powder : Zinc oxide Magnesium oxide Other oxides and Fluorides may be present Liquid : Phosphoric acid 30-40% Water ZnO or Al(OH)3 as buffering agents COMPOSITION:
  5. 5. ZINC-PHOSPHATE CEMENTZINC-PHOSPHATE CEMENT MANIPULATION:MANIPULATION:  Zinc-phosphate material is mixed onZinc-phosphate material is mixed on aa thick,cooled glass slabthick,cooled glass slab usingusing stainless steelstainless steel spatulaspatula (Freeze slab technique)(Freeze slab technique) toto ↑↑ W.T. andW.T. and S.T.S.T.  Powder is added to liquid small increment byPowder is added to liquid small increment by small increment to help insmall increment to help in buffering the acidbuffering the acid and toand to ↑↑ W.T. and S.T.W.T. and S.T.
  6. 6. ZINC-PHOSPHATE CEMENTZINC-PHOSPHATE CEMENT MANIPULATION: (Cont.d)MANIPULATION: (Cont.d) Mixing should be done over aMixing should be done over a wide areawide area to help in heat dissipationto help in heat dissipation ↑↑ W.T. andW.T. and S.T.S.T. Thin mixThin mix (by(by↑↑L/P ration)L/P ration) is used foris used for cementation purposescementation purposes Thick mixThick mix (by(by ↓↓L/P ratio)L/P ratio) is used asis used as cavity basecavity base oror temp. fillingtemp. filling
  7. 7. ZINC-PHOSPHATE CEMENTZINC-PHOSPHATE CEMENT MANIPULATION: (Cont.d)MANIPULATION: (Cont.d) PrecautionsPrecautions ………………….………………….;; 1.1. Liquid bottle should beLiquid bottle should be tightly closedtightly closed (Evaporation(Evaporation of water will reduce the reactivity of the cementof water will reduce the reactivity of the cement)) 2.2. Liquid withLiquid with Cloudy appearanceCloudy appearance discardeddiscarded 3.3. Shake the powder bottleShake the powder bottle before dispensing thebefore dispensing the correct ratio andcorrect ratio and never usenever use powder ofpowder of other cementsother cements (e.g. ZOE…)(e.g. ZOE…) oror of other manufacturerof other manufacturer
  8. 8. ZINC-PHOSPHATE CEMENTZINC-PHOSPHATE CEMENT SETTING REACTION:SETTING REACTION: ExothermicExothermic chemical reactionchemical reaction of acid-of acid- base typebase type ZnO + HZnO + H3POPO4 ZnZn3(Po(Po4))2 + H+ H2OO Set materialSet material is composed of ais composed of a matrix of zincmatrix of zinc phosphate saltphosphate salt infiltrated withinfiltrated with non-reacted zincnon-reacted zinc oxide particlesoxide particles that are responsible forthat are responsible for material’s opacitymaterial’s opacity
  9. 9. ZINC-PHOSPHATE CEMENTZINC-PHOSPHATE CEMENT SETTING REACTION: (Cont.d)SETTING REACTION: (Cont.d)  Control of setting timeControl of setting time 1.1. ↑↑ L/P ratioL/P ratio ↑↑ S.T.S.T. 2.2. ↑↑ Mixing RateMixing Rate ↓↓ S.T.S.T. 3.3. ↑↑ Particle sizeParticle size ↑↑ S.T.S.T. 4.4. ↑↑ TemperatureTemperature ↓↓ S.T.S.T. 5.5. ↑↑ Buffering of the liquidBuffering of the liquid ↑↑ S.T.S.T. 6.6. Presence of moisturePresence of moisture ↓↓ S.T.S.T.
  10. 10. ZINC-PHOSPHATE CEMENTZINC-PHOSPHATE CEMENT CHARACTERS:CHARACTERS: 1. Biological properties:  Fresh mix of zinc phosphate cement is highly acidic (pH 1.6-3.6) due to presence of strong phosphoric acid causes pulp irritation  In deep cavity, cavity liner should be used beneath  Thin mix is more irritant than thick mix  Set material becomes neutral within 48 hrs
  11. 11. ZINC-PHOSPHATE CEMENTZINC-PHOSPHATE CEMENT CHARACTERS: (Cont.d)CHARACTERS: (Cont.d) 2. Interfacial properties:  Zinc phosphate cement shows no chemical bonding either to tooth structure or restoration surfaces (Mechanical retention and physical adhesion) 3. Chemical properties:  Cement shows some degree of solubility , and it is dependant on L/P ratio (thin mix ↑ solubility)
  12. 12. ZINC-PHOSPHATE CEMENTZINC-PHOSPHATE CEMENT CHARACTERS: (Cont.d)CHARACTERS: (Cont.d) 4. Mechanical properties:  Zinc phosphate cement is stronger than ZOE (So it can be used for final cementation and as cavity bases), but it is weaker than glass ionomer and silico-phosphate cements 5. Esthetic properties:  Set cement is opaque (due to presence of non- reacted ZnO particles), so it can not be used for cementing ceramic restorations
  13. 13. ZINC-PHOSPHATE CEMENTZINC-PHOSPHATE CEMENT CHARACTERS: (Cont.d)CHARACTERS: (Cont.d) 5. Thermal properties:  Has low thermal diffusivity used as cavity bases under metallic restorations 6. Film thickness:  As low as 15 µm can be used for final cementation 7. Practicability:  Needs well-trend operator due to its short S.T.  Material is successfully used for a long time
  14. 14. ZINC-PHOSPHATE CEMENTZINC-PHOSPHATE CEMENT APPLICATIONS:APPLICATIONS: 1. Final cementation of cast metal restoration 2. Cavity base 3. Temporary filling material 4. Cementation of orthodontic bands 5. Build the lost dentine up under amalgam restorations.
  15. 15. ZINC-PHOSPHATE CEMENTZINC-PHOSPHATE CEMENT RELATED MATERIALS:RELATED MATERIALS:  Either copperEither copper (Copper cement)(Copper cement) or silver saltor silver salt (Silver cement)(Silver cement) is added to cement powderis added to cement powder  Resultant materials haveResultant materials have bactericidal effectbactericidal effect  They can be used forThey can be used for filling 1ry teethfilling 1ry teeth andand cementing orthodontic bandscementing orthodontic bands
  16. 16. B. SILICATE CEMENTB. SILICATE CEMENT  Results from theResults from the reaction of phosphoric acidreaction of phosphoric acid with fluoro-alumino-silicate glass powderwith fluoro-alumino-silicate glass powder  This type of cement was used asThis type of cement was used as estheticesthetic restorativerestorative long time agolong time ago  ItsIts drawbacksdrawbacks (Acidity, solubility, shrinkage,(Acidity, solubility, shrinkage, discolorationdiscoloration,…),…) andand thethe development of newdevelopment of new materialsmaterials ((Composite resin, Glass ionomer,..Composite resin, Glass ionomer,..)) limited its uselimited its use
  17. 17. C. SILICO-PHOSPHATE CEMENTC. SILICO-PHOSPHATE CEMENT  It is aIt is a hybridhybrid ofof silicatesilicate andand zinc phosphatezinc phosphate cementscements  Powder :Powder : Mixture of zinc oxide and alumino-Mixture of zinc oxide and alumino- silicate glasssilicate glass  Liquid:Liquid: Phosphoric acidPhosphoric acid  Applications:Applications: 1.1. Luting agentLuting agent 2.2. Filling of 1ry teethFilling of 1ry teeth 3.3. Die materialDie material
  18. 18. ACID-BASE REACTION CEMENTSACID-BASE REACTION CEMENTS II. Cements based on polyacrylic acidII. Cements based on polyacrylic acid (polyalkenoate cements)(polyalkenoate cements) A.A. Zinc polycarboxylate cementZinc polycarboxylate cement B.B. Glass-Ionomer cementGlass-Ionomer cement
  19. 19. Cements based on poly-acrylic acidCements based on poly-acrylic acid (polyalkenoate cements)(polyalkenoate cements) Zinc oxide Fluro-alumino- silicate glass Poly- acrylic acid Glass-Ionomer cement Zinc- polycarboxylate cement
  20. 20. CEMENTS BASED ON POLY-CEMENTS BASED ON POLY- ACRYLIC ACIDACRYLIC ACID CHARACTERS OF PAA:CHARACTERS OF PAA: 1. Viscous acid with higher molecular weight than that of phosphoric acid 2. Has lower acidity (higher pH) than phosphoric acid 3. Provide chemical adhesion with natural tooth structure, base metal alloys, and tin plated Noble metal alloys
  21. 21. CEMENTS BASED ON POLY-CEMENTS BASED ON POLY- ACRYLIC ACIDACRYLIC ACID ADHESION OF PAA-BASED CEMENTSADHESION OF PAA-BASED CEMENTS TO TOOTH STRUCTURETO TOOTH STRUCTURE Several postulations were drawn;Several postulations were drawn; Smith DC (1968):Smith DC (1968): ((The inventor of polycarboxylates)The inventor of polycarboxylates) ChelationChelation with Cawith Ca++++ of hydroxyapatiteof hydroxyapatite Beech DR (1973):Beech DR (1973): StrongStrong ionic bondsionic bonds between polyacrylate andbetween polyacrylate and surface Casurface Ca++++ of apatiteof apatite
  22. 22. CEMENTS BASED ON POLY-CEMENTS BASED ON POLY- ACRYLIC ACIDACRYLIC ACID ADHESION OF PAA-BASED CEMENTSADHESION OF PAA-BASED CEMENTS TO TOOTH STRUCTURE (Cont.d)TO TOOTH STRUCTURE (Cont.d) Wilson AD (1974):Wilson AD (1974): ((The inventor of glass ionomerThe inventor of glass ionomer )) Initial adhesion is achieved by formation ofInitial adhesion is achieved by formation of strong hydrogen bondingstrong hydrogen bonding, then, then replaced withreplaced with ionic bondsionic bonds after a period of timeafter a period of time Wilson et al. (1983):Wilson et al. (1983): Polyacrylic ions enter the molecular structure ofPolyacrylic ions enter the molecular structure of hydroxyapatite,hydroxyapatite, displacing and replacingdisplacing and replacing phosphate ionsphosphate ions
  23. 23. CEMENTS BASED ON POLY-CEMENTS BASED ON POLY- ACRYLIC ACIDACRYLIC ACID ADHESION OF PAA-BASED CEMENTSADHESION OF PAA-BASED CEMENTS TO TOOTH STRUCTURE (Cont.d)TO TOOTH STRUCTURE (Cont.d) Wilson and McLean (1988):Wilson and McLean (1988): Bonding of PAA toBonding of PAA to collagencollagen !!!!!! (bond to enamel(bond to enamel is better than bond to dentine)is better than bond to dentine) Geiger et al. (1993):Geiger et al. (1993): Formation of intermediateFormation of intermediate layer of Carbonato-layer of Carbonato- apatiteapatite between cement and dentinebetween cement and dentine
  25. 25. A. ZINC-POLYCARBOXYLATEA. ZINC-POLYCARBOXYLATE CEMENTCEMENT Powder :Powder : Zinc oxideZinc oxide Magnesium oxideMagnesium oxide Stannous fluorideStannous fluoride inin some productssome products Liquid :Liquid : Poly-acrylic acidPoly-acrylic acid (30-(30- 40%)40%) waterwater COMPOSITION AND PRESENTATION: 1. Powder / liquid system
  26. 26. ZINC-POLYCARBOXYLATEZINC-POLYCARBOXYLATE CEMENTCEMENT COMPOSITION: (Cont.d) 2. Single bottle system  Poly-acrylic acid is supplied as a dry powder blended with cement powder  This mixture is mixed with regular water to get a cement mix 3. Capsules  Recently available for automatic mixing
  27. 27. ZINC-POLYCARBOXYLATEZINC-POLYCARBOXYLATE CEMENTCEMENT MANIPULATION: Mixing of cement powder and liquid is carried out on a glass slab using a stainless steel spatula PAA is viscous and needs more effort during mixing of material Thin mix (P/L ratio= 1.5:1) used for cementing purposes Thick mix (P/L ratio = 2.5:1) used as cavity base
  28. 28. ZINC-POLYCARBOXYLATEZINC-POLYCARBOXYLATE CEMENTCEMENT MANIPULATION: (Cont.d)  Polycarboxylate cement adhere to stainless steel instrument, so any metallic instrument should be cleaned while cement still unset  To achieve better bonding to tooth structure; 1. Tooth surface should be cleaned and dried from saliva 2. Mixed cement should be applied to tooth structure as fresh as possible
  29. 29. ZINC-POLYCARBOXYLATEZINC-POLYCARBOXYLATE CEMENTCEMENT SETTING REACTION: Chemical reaction of acid-base type Zinc oxide + PAA → Zinc-polycarboxylate Set material: composed of zinc-polycarboxylate matrix with un-reacted zinc oxide particles dispersed in providing the cement its opacity Speed of the reaction is affected by temperature, P/L ratio, powder particle size, and mixing rate.
  30. 30. ZINC-POLYCARBOXYLATEZINC-POLYCARBOXYLATE CEMENTCEMENT CHARACTERS: 1. Biological properties:  Very little irritating effect on the pulp because 1. Large molecular size of PAA acid, hinders its passage through dentinal tubules 2. Lower acidity of the PAA 3. Chemical bonding of PAA to tooth enamel and dentine
  31. 31. ZINC-POLYCARBOXYLATEZINC-POLYCARBOXYLATE CEMENTCEMENT CHARACTERS: (Cont.d) 2. Interfacial properties: PAA provides chemical adhesion to tooth structure, base metal alloys, and tin-plated noble alloys 3. Chemical properties: Polycarboxylate cement is more soluble in water than zinc-phosphate cement
  32. 32. ZINC-POLYCARBOXYLATEZINC-POLYCARBOXYLATE CEMENTCEMENT CHARACTERS: (Cont.d) 4. Thermal properties: Set cement has low thermal diffusivity (can be used as cavity base) 5. Esthetic properties: Set cement is opaque due to presence of un- reacted zinc oxide particles → not used to lute ceramic restorations
  33. 33. ZINC-POLYCARBOXYLATEZINC-POLYCARBOXYLATE CEMENTCEMENT CHARACTERS: (Cont.d) 6. Film thickness: Similar to zinc-phosphate cement (15 µm ), so can be used for final cementation of cast metal restorations 7. Practicability: Little more difficult to mix than other cement with less viscous liquid
  34. 34. ZINC-POLYCARBOXYLATEZINC-POLYCARBOXYLATE CEMENTCEMENT APPLICATIONS: 1. Final cementation of cast metal restorations 2. Cavity base 3. Temporary filling material 4. Cementation of orthodontic bands