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Dental cement

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The dentine bond strength may be lower than polyacrylate because of technique sensitivity. ... Bond with the tooth surface by enamel an dentine bonding system. ... – PowerPoint PPT presentation

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Title: Dental cement


1
Dental cement
  • Dent Mat. II

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

6
Uses of dental cement
  • Filling
  • 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 (gt0.75mm) 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
16
HEAT
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 2.5-8 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
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25
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26
Characteristic properties
ADA specification NO.8 for Zinc phosphate cement
27
Effects of manipulation on some properties.
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)22HE ? ZnE2H2O

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

36
Manipulation
  • Paste/paste
  • 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
  • Temporary luting cement
  • Type II
  • Permanent cementation
  • Type III
  • Temporary restoration for a few days
  • Type IV
  • Cavity liner

38
ZOE
39
Specification requirements
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 35-55 MPa

41
EBA cement
  • Powder
  • Add 20-30 of aluminium oxide
  • Liquid
  • Add 50-60 ethoxybenzoic acid in eugenol
  • Compressive strength 55-75 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
  • Zinc oxide
  • Magnesium oxide
  • Stannous fluoride
  • Liquid
  • Aqueous solution of polyacrylic acid
  • Other carboxylic acid

45
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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
  • Calcium aluminum fluorosilicate glass
  • Liquid
  • 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
Polyacid liquid
Hydrogen ions
55
Gelation
Polyacid liquid
-COOH
Ca2
56
Gelation
  • Calcium ions have more reactivity than aluminium
    ions.
  • This is critical phase of contamination.

57
Hardening
Polyacid liquid
-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
  • 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
  • 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
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
  • Composite
  • Resin matrix inorganic filler

Silane coated
73
Composition
  • Filler
  • Silica
  • Matrix
  • 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
  • Chemical, light, or dual cure
  • Single paste
  • Light cure

76
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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
  • 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 9.2-11.7 Alkaline
  • Bactericidal
  • High solubility

83
Properties
  • Stimulate the secondary dentine formation in the
    area of thin dentine lt0.5mm
  • 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
  • ZOE gt Polycarboxylate gt Zinc phosphateGIC gt
    Resin cement
  • Irritation to pulp tissues
  • ResinZinc phosphate gt GIC gt Polycarboxylate gt
    ZOECalcium 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
    199981(5)597-609
  • White SN, Yu Z. Film thickness of new adhesive
    luting agents. J Prosthet Dent 199267(6)782-90
  • Ergin S, Gemalmaz D. Retentive properties of five
    luting cements on base and noble metal copings. J
    Prosthet Dent 2002885491-97
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