zinc phosphate cement(1)(1).pptxfghjjyuuioiuu

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1. ZINC PHOSPHATE CEMENT Presented by- Dr. Kranti R.Khadse Department Of Conservative DentistryAnd Endodontics Post Graduate Student

2. CONTENT: INTRODUCTION CLASSIFICATION AVAILABLE AS COMMERCIAL NAME COMPOSITION MANUFACTURE SETTING REACTION PROPERTIES MANIPUATION ADVANTAGE DISADVANTAGE APPLICATION MODIFICATIONS

3. INTRODUCTION Zinc phosphate is the oldest of the luting cements, and thus serves as a standard with which newer cements can be compared. Introduced by Dr. Otto Hoffman in 1800s , the cement has successfully been used for many years for temporary restorations and as a luting agent. mannapalli mahalakshmi+ sikri

4. Also known as – ZINC OXYPHOSPHATE CEMENT and CROWN AND BRIDGE CEMENT . ADA specification no. - 96 ( water settable cement ) previous specification no. for zinc phosphate cement - 8

5. TYPES The cement is of two types depending upon the particle size . Type I: • Cements are fine grained . • Film thickness should be 25 μm or less. • Used for luting. Type II: • Cements are medium particle sized. • Film thickness should not be more than 40 μ m . • used for luting and filling. mannapalli Why type 1 is used for Luting and type 2 for filling

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7. LUTING Direct restoration And indirect restoration. Luting is used for indirect R

8. ORTHODONTIC BAND ORTHODONTIC BRACKETS

9. BASE Placement of zinc phosphate base beneath Amalgam restoration

10. AVAILABLE AS : Powder and liquid system. Capsules of preproportioned powder and liquid Supplied in shades of yellow, grey, golden brown, pink and white. mannapalli

11. COMMERCIAL NAME: Confit Harvard Zinc cement (DPI) Modern tenacin Poscal (VOCO) De trey zinc (Dentsply) Hy bond DPI* ZINC CEMENT HARVARD DE TREY ZINC mannapalli

12. Powder Weight % Zinc oxide 90.2% - Principal constituent Magnesium oxide 8.2% - Aids in sintering Silicone dioxide 1.4% - Fillers aids in sintering Bismuth trioxide 0.1% Barium oxide Traces Barium sulphate Traces Improves smoothness of mix Calcium oxide Traces COMPOSITION sikri

13. Liquid weight % Phosphoric acid (free acid) 38.2% - React with zinc oxide Phosphoric acid 16.2% - Buffers, to reduce rate (combined with Aluminum of reaction and Zinc) Water 36.0% - Controls rate of reaction Aluminum 2.5% Zinc 7.1%

14. POWDER

15. Zinc oxide – is the principal ingredient of the zinc phosphate cement powder. - Other ingredients are added to control the working characteristics and the final properties of the mixed cement. Magnesium oxide – reduces the temperature of the calcination process. sikri

16. Silicone dioxide – acts as a inactive filler and aids in calcination process during manufacture. Bismuth trioxide – imparts smoothness to the freshly mixed cement mass but in large amounts may also lengthen the setting time.

17. LIQUID

18. The liquid is produced by adding aluminum and sometimes zinc or their compounds into orthophosphoric acid solution. Aqueous solution of Phosphoric acid: solution containing free phosphoric acid is generally very reactive . Water: The water controls the ionization of the acid , which in turn influences the reaction process of the liquid and powder.

19. Zinc and aluminum: Act as buffers and partially neutralize the pH of the phosphoric acid and reduce it’s reactivity. - This reduced rate of reaction results in a smooth, nongranular cement mass.

20. MANUFACTURE POWDER The ingredients are mixed and heated at temperatures between 1000 ºC and 1400 ºC ( Sintering ) ( Sintering is the process of compacting and forming a solid mass of material by heat or pressure without melting it to the point of liquefaction.) Pores between particles are reduced in size Partical bonding is initiated at contact points Fully sintered

21. . After sintering, the cake formed is cooled quickly This causes the material to crack which helps in grinding of the material to a fine powder. ( Fritting ) Powder Particles Frit

22. When the powder is mixed with liquid, Phosphoric acid attacks the surface of the particles and releases Zn ions into the liquid. Aluminum which already forms a complex with the phosphoric acid reacts with zinc and form a zinc aluminophosphate gel. The reaction is exothermic. SETTING REACTION : philips

23. Set cement consists of zinc phosphate matrix in which unreacted ZnO powder particles are embedded

24. MIXING, WORKIG AND SETTING TIMES OF ZINC PHOSPHATE CEMENT

25. MIXING TIME: 1 min. 15 seconds. The mixing procedure starts and ends with small increments in order to control the setting reaction and to dissipate the heat evolved in the reaction.

26. WORKING TIME : Working time is measured as the time from the start of mixing to the maximum time at which the viscosity (consistency) of the mix is still low enough to flow readily under pressure to form a thin film. The rate of matrix formation dictates the length of working time. philips

27. SETTING TIME: The time period from the start of the mix to the time when the mix reaches it’s desired consistency/hardness . Clinically, this represents the time at which the excess zinc phosphate cement should be removed from the margins of the restoration . A reasonable setting time: 2.5 - 8 min . philips

28. Generally, it is desirable to extend the setting time of the cement to provide sufficient working time for manipulation. Various methods are employed to delay this setting time and prolong this working time. Under the control of the manufacturer. Under the control of the operator.

29. UNDER THE CONTROL OF THE MANUFACTURER: • S intering temperature: Higher ( ↑ ) the temperature - more slowly the cement set. • Water content in the liquid: presence of, excess water - accelerates the reaction ( ↑ ), insufficient water - retards the reaction ( ↓ ). mannapalli

30. • Buffering agents: The buffering agents in the liquid, control the number of phosphate groups available for reaction and slow down the reaction . • The particle size of the powder : Finer the particles size react more quickly because greater surface area is exposed by the liquid.

31. UNDER THE CONTROL OF THE OPERATOR: • Powder/liquid ratio: A larger ( ↑ ) powder/liquid ratio greatly improves the properties of the mixed cement, therefore the maximum possible powder should be used to obtain a particular consistency. The powder/liquid ratio for filling is 2.5:1 and for luting is 1.5:1 More the liquid, slower the reaction. Nisha garg

32. • Rate of powder incorporation: If all the powder is added at one time, the reaction is very rapid. The reaction is slower if the powder is incorporated slowly. Introduction of a small quantity of powder into the liquid increases the setting time, by reducing the amount of heat generated especially for first few increments. sikri

33. • Water contamination or loss of water: Addition of water - decreases ( ↓ ) setting time, and loss of water - increases ( ↑ ) setting time. • Mixing temperature: higher ( ↑ ) temperature - accelerate ( ↑ ) the reaction . cooling the glass slab is the most effective ways of slowing the reaction and prolonging the working time. sikri

34. FROZEN GLASS SLAB TECHNIQUE: This method is applied ,where long working time and shorter setting time is required. In this method Glass slab is cooled in a refrigerator at 6 ºC or in a freezer at 10 ºC. The powder and liquid are dispensed onto this slab without removing the condensed moisture. mahalakshmi

35. The amount of powder incorporated in this method is 50% - 75% more than normal . However, incorporation of the condensed moisture into the mix counter acts the higher P/L ratio. The compressive and tensile strengths and solubility are not significantly different from the normal values. Working time for this method is increased by 4 -11 minutes for slab temperatures ranging from 6C – 10 C .

36. • Spatulation time: - Prolonging ( ↑ ) the spatulation time destroys the forming matrix. - Fragmentation of the matrix needs extra time to rebuild the bulk of matrix. sikri

37. PROPERTIES PHYSICAL PROPERTIES: Mechanical properties : Compressive strength: High -104 – 119 MPa Set cement Gain maximum (70%) strength in first 30 minutes. . mannapalli

38. Tensile strength: Low - 5.5 MPa Set cement is weaker in tension thus making it brittle. Modulus of elasticity (Stiffness): High -13.7 GPa Makes it stiff and resistance to elastic deformation.

39. FACTORS AFFECTING STRENGTH : P/L Ratio: A reduction in the P/L ratio of the mix produces a markedly weaker cement. Water content of the liquid: Loss or gain - reduces both the compressive strength and the tensile strength of the cement. mannapalli

40. SOLUBILITIES : High solubility of the cement can lead to marginal leakage around restorations specially when it is used as luting agent. The solubility is greater in dilute organic acids, like lactic, acetic and especially citric acids, all of which are present in the human diet. The cement is highly soluble in water for the first 24 hours after setting and loss of material can range from 2.4% to 3.3%.After this the solubility is negligible (0.2%) mahalakshmi+ mannapalli

41. FACTORS AFFECTING SOLUBILITY: P/L ratio : Thicker mixer - ↓ solubility Water content of liquid : Any change in water content –(↑) solubility Effect of moisture contamination : Premature contact of the incompletely set cement with water ( ↑ ) dissolution and leaching of the surface. Apply varnish over the exposed surface. mannapalli

42. ADHESION: Setting of Zinc phosphate cement does not involve any reaction with surrounding hard tissue or other restorative materials. Therefore bonding occurs by mechanical interlocking at interfaces, not by chemical interactions, and any coating applied on the tooth surface for pulp protection reduces retention.

43. BIOLOGICAL PROPERTIES: The cement has the potential to cause inflammation of the pulp, due to the presence of acid. pH of the cement: Due to presence of the phosphoric acid, the acidity of zinc phosphate cement is quite high in deep cavities and at the time when a prosthesis is placed on a prepared tooth. mannapalli

44. Two min after the start of the mixing, the pH of the cement is approximately 2 . The pH then increases rapidly, but still is only about 5.5 at the end of 24 hrs. From these data it is evident that any damage to the pulp from acid attack by zinc phosphate cement probably occurs during the first few hours after insertion .

45. TIME (MIN) ZINC PHOSPHATE ZINC SILICOPHOSPHATE 2 2.14 1.43 15 3.30 2.46 30 3.71 2.79 60 4.34 3.60 pH OF CEMENTS FOR LUTING APPLICATIONS: The pH reaches neutral at 48 hours. philips

46. Pulpal response: Moderate Pulpal protection: Dentin is protected against infiltration of this acid to protect pulpal injury. Pulp protection should be carried out in deep cavities through use of an intervening varnish, liner or base, such as- • Zinc oxide eugenol • Calcium hydroxide • Cavity varnish mannapalli

47. Avoid thin mixes . An anesthesia should be used for some patients which are very sensitive to the phosphoric acid. (cementation of crown or FPD in vital teeth cause severe sensitivity or pain.)

48. THERMAL PROPERTY: It is an good thermal insulator but in thickness of 1mm or more. It is a poor electrical insulator (galvanic effects) due to it’s porosity which accomodatates moisture, thus encouraging electron transport . OPTICAL PROPERTY: Cement is Opaque and does not represent tooth colored materials. mannapalli

49. DIMENSIONAL STABILITY: This expansion is then followed by shrinkage in order to 0.04% - 0.06% in seven days.

50. MANIPULATION: Stainless steel spatula and clean cool glass slab are use for mixing. The recommended P/L ratio - about 1.4 gm powder/ 0.5 ml liquid. ( The powder/liquid ratio for filling is 2.5:1 and for luting is 1.5:1) mannapalli

51. It is probably not necessary to use a measuring device for proportioning the powder and liquid because the desired consistency may vary to some degree with the clinical situation. A cool mixing slab should be employed. The cool slab prolongs the working and setting times and permits the operator to incorporate the maximum amount of powder before matrix formation proceeds to the point at which the mixture stiffens.

52. The liquid should not be dispensed onto the slab until mixing is to be initiated because water will be lost to the air by evaporation. Powder is measured and dispensed with scoop in small increments, a liquid is dispensed as drops . Cement mixing is done on cool glass slab with a narrow bladed stainless steel spatula using circular brisk motion .

53. Powder is divided into 5 to 8 increments in which initial two increments are smaller, third and fourth increments are bigger one and after that increments are again smaller in size. Initial increments are smaller in size so as: – To achieve the slow neutralization of the liquid. – To control the reaction.

54. Middle increments are larger in size so as to further saturate the liquid to form zinc phosphate. Because of presence of less amount of unreacted acid, this step is not affected by heat released from the reaction. In the end, the smaller increments of powder are added so as to achieve optimum consistency.

55. After dividing powder, dispense liquid on the glass slab. While dispensing, the liquid bottle should be held vertical and close to the powder . Repeated opening of the liquid bottle or early dispensing of the liquid prior to mixing should be avoided because evaporation of liquid can result in changes in water/acid ratio which can further result in decrease in pH and an increase in viscosity of the mixed cement.

56. Each increments are mixed for 15 – 20 seconds. Since setting reaction is an exothermic type, the heat accelerate setting reaction So, it is very important to dissipate this heat which can be done by, – Using chilled glass slab. – Using smaller increment for initial mixing of cement. – Large area of glass slab is covered during mixing.

57. For luting, mixing is continued until a “1 inch string” is formed when spatula is pulled away from the glass slab.

58. For base, consistency should be such that it can be rolled into a ball without sticking.

59. Luting of restorations, such as Inlays Crowns Fixed dental prosthesis. Luting of orthodontics bands and brackets. High strength bases. Temporary restorations. APPLICATION: mannapalli

60. ADVANTAGES: Long record of clinical acceptability. This cement has High compressive strength [104 – 119MPa], hence it is used as a base under amalgam restorations since it can withstand the condensation forces during it’s placement. Thin film thickness. Relatively low solubility compared to GIC ( Glass ionomer cement) and ZOE ( Zinc oxide eugenol) cements. mahalakshmi

61. DISADVANTAGES: Pulpal irritation due to Low initial pH. Brittle in nature with low tensile strength[5.5 MPa ]. Lack of an adhesion to tooth structure – No chemical adhesion. Lack of anticariogenic effect. Mannapalli+ mahalakshmi

62. Soluble in water. Poor esthetic: can not be used with translucent(all ceramic) restorations like crowns and veneers . The low pH cause gross decalcification

63. MODIFIED ZINC PHOSPHATE CEMENTS

64. 1. FLUORIDATED CEMENTS

65. Fluorides, such as stannous fluoride etc, are added to zinc phosphate powder. ( Fluoride derive from soil, water and food. ) The approximate concentration of fluoride is 10% . Fluoride release continues over a long period and fluoride uptake results in reduced enamel solubility and increased hardness. sikri

66. Translucent and more esthetic than zinc phosphate cement. Anticariogenic because remineralized enamel, prevent cavity and reverse early sign of tooth decay. ADVANTAGE: Lower strength. higher solubility. (than conventional zinc phosphate cements.) Stannous fluoride is not so long lasting used. DISADVANTAGE:

67. COPPER CEMENTS

68. Copper cements are basically modified zinc phosphate cements. Silver salts or copper oxide are sometimes added to the powders of the zinc phosphate cements to increase their antibacterial properties . Sikri+ mannapalli

69. COMMERCIAL NAME: Ames ( with 97 % copper content.) Doc’s Best (Red and White cement kit ).

70. Copper cements consist- cuprous oxide ( red ) or cupric oxide ( black ) added to the zinc oxide powder. Other salts of copper, cuprous iodide ( white ) and siliceous oxide ( green ) COMPOSITION:

71. Silver salts have also been used for these purpose. There is little evidence for any advantage of these cements over conventional cements. The main object of addition of copper is to render the cements germicidal in the mouth. Copper and silver are both bacteriostatic , but the longevity of their action is questionable. sikri

72. MANIPULATION: The chemistry of the copper cement is very similar to that of the zinc phosphate cements and they are manipulated in the same manner . mannapalli

73. APPLICATION: Filling in children. Intermediate restoration. Indirect pulp capping. As base beneath composite restorations.

74. PROPERTIES: They are bactericidal or bacteriostatic. Biological properties : They have poor biological properties. Because its ph is 5.3 , it is irritant to the pulp. It was highly acidic and toxic to the cell, due to the extremely high copper content ( 97% ) such as Ames, so now a days it’s used was banned. (renewed interest in copper cement recently with lower copper content ( 2% ). it is safe and is specially recommended for indirect pulp capping and where there is active caries .) mannapalli

75. 3. ZINC SILICOPHOSPHATE CEMENTS These materials are a combination of zinc phosphate cement and silicate cements , also known as silicophosphate cement. Zinc silicophosphate cements (ZSPC) consist of a mixture of silicate glass and zinc phosphate cement. sikri

76. TYPES Type I : For use as a cementing medium . Type II : For use as a temporary filling material . Type III : For dual use – cementing medium and temporary filling material.

77. COMPOSITION: Powder - Acid soluble silicate glass, - Zinc oxide - Magnesium oxides. silicate glass contains 13 to 25 percent fluoride Liquid - Phosphoric acid (50%). - Zinc (4-9%) - Aluminium (2%) Some materials have been labeled ‘germicidal’ because of the presence of small amounts of mercury or silver compounds.

78. MANIPULATION The powder is incorporated into liquid in two or three large increments on a cool glass slab and spatulated to produce a thick paste for fillings or a thin paste for luting.

79. SETTING REACTION Has not been fully investigated but the set cement seems likely to consist of unreacted glass and zinc oxide particles bonded together by an aluminophosphate gel containing zinc, calcium, aluminium and fluoride ions.

80. PROPERTIES: Compressive strength of the set cement is appreciably higher than the zinc phosphate cement. These materials are tougher and more abrasion resistant than zinc phosphate cements. Solubility under clinical conditions is less than that of zinc phosphate cements. Better adaptation to the tooth structure.

81. Fluoride release is evident. The set cement is more translucent than the opaque zinc phosphate. The mix is highly acidic and the pH remains low, after setting for prolonged periods of time. The disadvantage of this cement is higher film thickness and greater potential for pulp irritation.

82. APPLICATION: - Rampant caries.

83. ZINC POLYCARBOXYLATE CEMENT (FIG. 15.12) Zinc polycarboxylate cement is also known as zinc polyacrylate cement. It was one of the first chemically adhesive dental materials introduced in the 1960s. It sets by an acidbase reaction between a powder and a liquid. It bond to the tooth structure because of chelation reaction between the carboxyl groups of the cement and calcium present in the tooth structure. This implies that more mineralized the tooth structure, the stronger the bond. Figure 15.10: For luting, the consistency should be such that “1 inch” string should be formed when spatula is taken away from glass slab Figure 15.11: For base/restoration, consistency should be such that it can be rolled into the ball without sticking Vimal Sikri Philips Nisha garg Mannapalli Mahalakshmi REFERENCES: