1. Dental cement
dr shabeel pn

2. Topic General requirements for dental cements
Classification of dental cements
Component and properties
Setting reaction
Mixing process
The uses of dental cements

3. Definition
Dental cements : materials made from two components, powder and liquid, mixed together.

4. Powder + Liquid
Pastelike or flowable material
Hardens to a rigid solid

5. Uses of dental cements Luting agent Pulp protection or cavity sealer
Temporary cement
Permanent cement
Pulp protection or cavity sealer
Cavity varnish
Liner
Base

6. Uses of dental cement Filling Others Temporary filling
Permanent filling
Others
Root canal sealer
Calciumhydroxide cement
Bite registration material

7. Luting agent
Luting : the use of moldable substance to seal a space between two component.
Most dental treatment necessitate attachment of prostheses to the teeth by means of luting agent.

8. General requirements for luting agents
Biocompatibility
Retention
High tensile strength, fracture toughness, fatique strength
Good marginal seal

9. General requirements for luting agents
Low film thickness
Ease of use
Radiopacity
Aesthetics

10. Film thickness The thickness of film between two flat surface
The maximum allowable thickness is 25 µm (ADA specification No. 96)
Low film thickness value is preferred

11. Cement base
A thick layer of cement (>0.75mm) is applied under restoration to protect pulp against injuries.
The base should be strong enough to resist the condensation force during the placement of restoration.
Well insulation ability
Good sealing

12. Classification of dental cements
Conventional cement
Zinc phosphate cement
Zinc oxide-eugenol cement
Polycarboxylate cement
Glass ionomer cement
Resin-base cement
Resin cement
Resin modified glass ionomer cement

13. Conventional cement Typically powder/liquid system Liquid is an acid
Powder is a base ; insoluble in oral fluid
When mixed together  Acid-base reaction

14. Zinc Phosphate cement

15. Zinc phosphate cement Powder Liquid Zinc oxide Phosphoric acid
Magnesium oxide
Water
Alumenium phosphate

16. ZnO
HEAT
Zn+
Zinc
aluminophosphate
gel

17. Unreacted
ZnO
Unreacted
ZnO
Unreacted
ZnO
Unreacted
ZnO
Zinc aluminophosphate matrix

18. Setting reaction Exothermic reaction
Adding of water can accerlate the reaction.
Loss of water can lengthen the setting reaction.

19. Working time and setting time
Working time commonly is 3-6 minute
Setting time is minute(ADA specification No.96)
Depending on the manufacturer instruction

20. 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.

21. 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.

22. Mixing procedure Second : Larger amount of powder is added to liquid
For further saturation of liquid to newly form zinc phosphate.
This steps may not effect by heat released from the reaction.
{because of the less amount of unreacted acid}

23. Mixing procedure Finally: the small amount of powder is added again
To control the optimum consistency

24. 1 2 3 4 5 6 7 8

25. 4 5 2 3 7 6 8 1

26. Characteristic properties
Setting time at 37O
5 – 9 minutes
Minimum compressive strength
75 MPa
Maximum film thickness
25 µm (for luting the prostheses)
Maximum Solubility
0.2% by weight
ADA specification NO.8 for Zinc phosphate cement

27. Effects of manipulation on some properties.
Manipulative variables
Properties
Copressive strength
Film thickness
Solubility
Initial acidity
Setting time
Decreased powder/liquid ratio
Increase rate of powder incorporation
Increase mixing temperature
Water contamination

28. Biocompatibility
Acid can penetrate into the dentinal tubule  irritate pulp
pH of cement
Liquid = 2.0
3 minutes after mixing = 4.2
1 hour = 6
48 hours = 7

29. Modified zinc phosphate cement
Fluoride cement
Add Stannous fluoride
Higher solubility/ Lower strength
Zinc silicophosphate
Zinc phosphate + Silicate
Higher strength/ lower solubility
Fluoride released
Translucency

30. Clinical applications
Zinc phosphate cement
Luting agent
Base and temporary filling
Modified zinc phosphate
Luting prostheses
Luting the orthodontics band

31. Zinc oxide-eugenol cements
Lower strength than Zinc phosphate cement.
Sedative effect
Usually used as temporary filling

32. Zinc oxide-eugenol cement
Simple ZOE
Reinforced ZOE
EBA cement

33. Compositions of simple ZOE
Powder
Zinc oxide
Rosin : reduce the brittleness of the set cement
Zinc stearate : plastcizer
Zinc acetate : improve strength
Liquid
Eugenol and olive oil

34. Setting reaction First ZnO + Eugenol -- water Zn(OH)2 Second
Zn(OH)2+2HE  ZnE2+H2O

35. Setting reaction Water accelerates the reaction
Zinc eugenolate is easily hydrolized by moisture

36. Manipulation Paste/paste Powder/liquid
Mix two equal pastes together until it obtains the homogeneous color.
Powder/liquid
Usually 4/1 for maximum strength
Mix the large increment, firstly
Not require cool glass slap

37. Classification Type I Type II Type III Type IV Temporary luting cement
Permanent cementation
Type III
Temporary restoration [for a few days]
Type IV
Cavity liner

38. ZOE

39. Specification requirements
Type
Setting time [min]
Compressive strength
[MPa]
Solubility
[%]
Film thickness
[µm]
Type I
4-10
35 maximum
2.5 25
Type II
1.5
Type III -

40. Reinforced ZOE Used as the intermediate restorative materials (IRMTM)
Add 10-40% resin polymer in the powder for strengthening the set cement
Compressive strength MPa

41. EBA cement Powder Liquid Compressive strength 55-75 MPa
Add 20-30% of aluminium oxide
Liquid
Add 50-60% ethoxybenzoic acid in eugenol
Compressive strength MPa

42. Clinical applications
Base
Temporary cementation
Permanent cementation
If cement contains eugenol, it is not to use with resin restorative material.

43. Zinc polycarboxylate cement
Or called Zinc polyacrylate cement
The first adhesive cement
Bond to tooth structure and metal
More biocompatibility than zinc phosphate cement
Polyacrylic acid have more molecular weigth
Moderate strength/ moderate solubility

44. Composition Powder [the same as zinc phosphate cement ] Liquid
Zinc oxide
Magnesium oxide
Stannous fluoride
Liquid
Aqueous solution of polyacrylic acid
Other carboxylic acid

46. Manipulation
Mix first half of powder to liquid to obtain the maximum length of working time.
The reaction is thixotropic
The viscosity decreases when the shear rate increases

47. Setting reaction Like zinc phosphate cement
Retarded by cool environment

48. Bonding to tooth structure
The polyacrylic acid is believed to react with calcium ion via the carboxyl group.
The adhesion depends on the unreacted carboxyl group.

49. Specification requirements
Setting time at 37OC: 9 minutes
Maximum film thickness: 25µm
Minimum compressive strength: 50 MPa
Maximum solubility: 0.2%

50. Applications Cement inlays or crowns Used as base Temporary filling
Lute the stainless steel crown

51. Glass ionomer cement Or called Polyalkynoate cements
Conventional glass ionomercement
Resin-modified glass ionomer cement [RMGICs]
Powder + Liquid/ Powder + water/ Encapsulated

52. Composition Powder Liquid Calcium aluminum fluorosilicate glass
Polyacid
Copolymer of polyacrylic / itaconic acid
Copolymer of polyacrylic / maleic acid
Add tartaric: accelerator

53. Setting reaction There are three stages: Dissolution Gelation
Hardening.
Water hardening or water setting

54. Dissolution Ca2+ Al3+ F- Polyacid liquid Glass core Silica gel
Hydrogen
ions
Ca2+
Al3+ F-
Silica gel
Glass core

55. Gelation
Polyacid liquid
Cross-linked
polyacid
-COOH
Ca2+
Al3+ F-

56. Gelation Calcium ions have more reactivity than aluminium ions.
This is critical phase of contamination.

57. Hardening
Polyacid liquid
Cross-linked
polyacid
-COOH
Al3+

58. Hardening Last as long as 7 days.
The reaction of aluminium ions provides the final strength of set cement.

59. Glass core
Cross-linked polyacid
Silica gel

60. Properties
Film thickness is similar or less than zinc phosphate cement.
Setting time 6 to 8 minutes from start of mixing.
Less pulpal irritation.
Bacteriocidal or bacteriostatic.
Prevent caries.

61. Strength
The 24-hour compressive strength is greater than zinc phosphate cement.
The compressive strength increase to 280MPa between 24 hours to 1 year after initial setting.

62. Bonding It can be chemically bonded to the tooth structure.
The mechanism of bonding is the same as polyacrylate cement.
The dentine bond strength may be lower than polyacrylate because of technique sensitivity.

63. Modified GI Cermet Resin-modified GI Combination of glass and metal
No significantly improve the strength
More wear resistance and short setting time
Resin-modified GI

64. Resin-modified glass ionomer cement
Add polymerizable function groups
Both chemical & light curing
Overcome moisture sensitive & low early strength
Names: Ligth cured GICs, Dual-cured GICs, Tri-cured GICs, Hybrid ionomer, Compomers, Resin-ionomers

65. Setting reaction Polymerization Acid-base reaction
initial setting
Acid-base reaction
maturing process & final strength
Heat released from the polymerization reaction.

66. Properties Higher strength than conventional GI
Higher adhesion to resin material
Less water sensitivity
Can be polished after curing

67. Relative properties of a glass ionomer and a resin-modified GI cements
Property
GIC
RMGIC
Working time
2 min
3 min 45 sec
Setting time
4 min
20 sec
Compressive strength
202 MPa
242 Mpa
Tensile strength
16 Mpa
37 Mpa

68. Applications Type I : Luting agent Type II : Filling material
Type III : Base and liner

69. Conventional GI for cementation

70. GI filling material

71. Adhesive resin cement Occur later from the direct filling resin
Become popular because of the improved properties, high bond strength.
Resin cement is flowable composite resin.

72. Composite resin cement
Resin matrix + inorganic filler
Silane
coated

73. Composition Filler Matrix Silica Bis-GMA (polymer)
The fillers binds with matrix by
silane coupling agent

74. Setting reaction Polymerization Chemical activation Light activation
Dual activation [chemical and light]

75. Preparations Powder / liquid Chemical, light, or dual cure
2 paste system [base / catalyst]
Single paste
Light cure

77. Bonding system
Bond with the tooth surface by enamel an dentine bonding system.
Bond with metal by using metal primer.
Bond with ceramic restoration by treating the surface of porcelain with silane coupling agent

78. Properties Very good bond strength High compressive strength
Water sensitive
Might irritate pulpal tissues

79. Applications
Tooth color filling materials
Luting cements

80. Calcium hydroxide cement
Used as base and liner
High pH value
Good biocompatibility

81. Composition 2 Pastes system Base Catalyst Salicylate  reaction
Calcium tungstate and barium sulfate
 radiopacity
Catalyst
Calcium hydroxide

82. Properties Lower compressive strength than others
Resist to the condensation force of amalgam filling
High pH [Alkaline]
Bactericidal
High solubility

83. Properties
Stimulate the secondary dentine formation in the area of thin dentine [<0.5mm]
Stimulate the dentine formation in the exposed-pulp lesion [Direct pulp capping]

84. Comparable properties of cements

85. Compressive strength [MPa]
Zhen Chun Li and Shane N. White, 1999

86. Bond strength Separation forces [MPa]
Sule Ergin and Deniz Gemalmaz, 2002

87. Film thickness [µm]
Shane N. White, Zhaokun Yu, 1992

88. Others Solubility Irritation to pulp tissues
ZOE > Polycarboxylate > Zinc phosphate~GIC > Resin cement
Irritation to pulp tissues
Resin~Zinc phosphate > GIC > Polycarboxylate > ZOE~Calcium hydroxide

89. References Textbooks Kenneth J. Anusavice
Phillips’ science of dental materials
11th edition
W.B. Saunders company 2003

90. References Textbook Robert G. Craig Restorative dental materials
9th edition
Mosby company 1993

91. References Textbook Richard van Noort Introduction to dental materials
2nd edition
Mosby company 2002

92. References
Journals
Li ZC, White SN. Mechanical properties of dental luting cements. J Prosthet Dent 1999;81(5):
White SN, Yu Z. Film thickness of new adhesive luting agents. J Prosthet Dent 1992;67(6):782-90
Ergin S, Gemalmaz D. Retentive properties of five luting cements on base and noble metal copings. J Prosthet Dent 2002;885:491-97