3. INTRODUCTION
Cement is a material which bonds other substances together
In dentistry, the term ‘cement’ has been applied traditionally to powder-liquid
materials; which are mixed to a paste consistency and set to a hard mass
and used clinically to restore teeth either alone or with other materials (mixed
to a secondary consistency) and to attach pre-formed restorations or
appliances in a fixed position within the mold
Materials that set intra-orally and that are commonly used to join a tooth
and a prosthesis
10. OIL BASED CEMENTS
Zinc Oxide – Eugenol Cements Noneugenol – Zinc Oxide Cements
High-strength bases Provisional restorations (esp. for teeth that will
have bonded permanent restorations)
Provisional restorations Root canal sealers
Root canal sealers Gingival tissue packs
Gingival tissue packs Surgical dressings
Surgical dressings
11. ACCORDING TO SETTING REACTION
I. Acid-base reaction cements
II. Polymerizing cements
III. Dual cure cements
IV. Tricure cements
12. ACID BASE REACTION CEMENTS
Powder and liquid
Powder: base
Liquid: acid
P+L = acid base reaction
viscous paste
hardens to a solid mass
13. POLYMERIZING CEMENTS
Set by polymerizing reaction
Light activated / chemically activated
Eg.: resin cements
14. DUAL AND TRICURE CEMENTS
Dual cure cements: Sets by acid base and any of the polymerization
reactions (light / chemical activation)
Tricure cements: Uses all 3 mechanisms (acid-base + light activation +
chemical cure) for hardening
16. GENERAL PROPERTIES OF CEMENTS
1. Film thickness and consistency
2. Viscosity
3. Setting time
4. Strength
5. Solubility
6. Modulus of elasticity (MOE)
7. Biological properties
8. Fluoride release
17. FILM THICKNESS AND CONSISTENCY
• Film thickness determines the adaptation and retention of restoration to the
tooth
• Maximum thickness is 25 μm
• The heavier the consistency, greater the thickness
The ultimate film thickness that a well-mixed, non-granular cement attains
depends on:
Particle size of the powder
Concentration of the powder in the liquid
Viscosity of the liquid and
Consistency of the cement
18. FILM THICKNESS AND CONSISTENCY
• Consistency of the cement used in the cementation of a casting is critical
• In powder-liquid type of cement, an increased amount of powder
incorporated in liquid will increase the consistency of the cement mass
19. VISCOSITY
• The consistency of cements can be quantified by measuring viscosity
• Increase in temperature and time have both been shown to increase the
viscosity of some cements
• Delay in cementation can result in larger values of film thickness and
insufficient seating of the restoration
• For resin cements, viscosity can vary widely and some products come with
a choice of different viscosities
20. SETTING TIME
Of equal importance to the viscosity of the cement is its setting time
A sufficient time must be available after mixing:
to seat and finally adapt the margins of a restoration
to seat and adjust a series of orthodontic bands
or to properly contour a base of provisional restoration
Adequate working time is expressed by net setting time, as determined by
ANSI (American national standards institute) / ADA specification no. 96 and
based on a luting consistency, in between 2.5 and 8 mins. at a body temp. of
37° C
21.
22. SETTING TIME
Net setting time allows final finishing procedures associated with the
restoration
The 1st 60-90 seconds are consumed by mixing the cement
So, the net setting time is the time elapsed between the end of mixing and
time of setting
23. STRENGTH
ANSI / ADA Specification No. 96 (ISO 9917) stipulates that the standard
luting consistency of a dental cement must exhibit a minimum 24 hour
compressive strength of 70 Mpa
24. SOLUBILITY
Solubility in water and oral fluids is also an important consideration in
cement properties
Water-based cements are more soluble than oil-based
ANSI / ADA Specification No. 96 allows a maximum rate of acid erosion,
which is variable for different types of cements, when a cement is subjected
to lactic acid erosion by an impinging jet technique
25.
26. MODULUS OF ELASTICITY
• This is the measure of the stiffness of a cement
• Cements under ceramic crowns should have sufficient stiffness to withstand
masticatory loads
• A low MOE can result in flexing of the restoration resulting in fracture
27. FLUORIDE RELEASE
• Most of the cements contain Fluoride
• Gradually released over a period of time to impart adjacent tooth structure
with caries resistance
Eg.: Glass Ionomer cement
33. ZINC PHOSPHATE CEMENT
Traditional crown and bridge cement
Uses:
– Permanent cement for indirect restorations including inlays, onlays, crowns,
and bridges
– Orthodontic cement
– High-strength base
34. CLASSIFICATION
According to A.D.A no. 8
Type I: fine grain cement
Has finer particles capable of forming film thickness of 25 μ or less: cementation of precision fitting
castings
Type II: medium grain cement
Maximum allowable thickness is 40 μ (micron)
Cementation of orthodontic bands / thermal insulating bases
35. AVAILABLE AS
• Powder and Liquid form
• Capsules for pre-proportioned Powder and Liquid
36. COMPOSITION
POWDER:
INGREDIENTS % FUNCTIONS
1. ZnO (zinc oxide) 90.2% Reactive ingredient
2. MgO (magnesium oxide) 8.2% To reduce the temp. of calcination process
3. SiO2 (silicon dioxide) 1.4% Inert filler / reinforcing filler
4. Bi2O3 (bismuth trioxide) 0.1% Smoothness impartment to the freshly mixed cement mass and
in larger amount it may also lengthen the setting time
5. BaO / BaSO4 / CaO 0.1% Modifier, radio-opacity
6. Color pigments. Eg.: CuO
(copper oxide), MnO2 (
manganese dioxide)
Traces CuO, MnO2 and platinum black produce shades of grey
Bismuth oxides or certain chromates: yellow
Iron oxide: brown or green
37. COMPOSITION
LIQUID:
INGREDIENTS % FUNCTIONS
1. Orthophosphoric acid 38.2% Reactive ingredient
2. Zn3 (PO4)2 (zinc
phosphate) / AlPO4
(aluminium
phosphate)
16.2% a. Stabilize the pH of acid against the effects in changes of concentration
due to evaporation or condensation of water
b. Reduce its reactivity by partial neutralization of phosphoric acid
• This produces smooth, non-granular workable cement during mixing
3. Pure zinc 7.1% Moderator of the reaction between powder and liquid allowing adequate
working time and permitting sufficient quantity of powder to be added for
optimum properties
4. Pure alumina 2.5% It is essential to the cement forming reaction and assist in the formation of
an amorphous reaction product (zinc alumino phosphate) which forms
stronger cement
5. Water Controls the ionization of liquid and influences the rate of reaction, i.e. the
presence of an additional water shortens the setting time whereas
insufficient amount of water results in a prolonged setting time
38. SETTING REACTION
• ZnO+ aluminophosphoric acid Zinc alumino phosphate gel + heat
(powder) (liquid) (reaction matrix)
• When mixed, phosphoric acid dissolves the zinc oxide, which reacts with the
aluminum phosphate and forms zinc aluminophosphate gel on the remaining
undissolved zinc oxide particles.
• Loss of water from the liquid lengthens the setting reaction and vise versa.
• Mixing Time : 1.5 –2 mins.
• Setting Time : 2.5 –8 mins.
• Exothermic Reaction
39. SETTING REACTION
Note :
• The liquid controls the pH and the rate of the liquid-powder (acid-base)
reaction.
• Finer the particle size, faster the cement sets.
40. MANUFACTURE
• The ingredients are mixed and heated at temperature between 1000° C-1400° C.
(SINTERING)
• After this, cake formed is cooled quickly.
• This causes material to crack which helps in grinding of the fine material to a fine
powder. (FRITTING)
46. FROZEN SLAB TECHNIQUE
In this technique, a glass slab is cooled in a refrigerator at 6 ° C or a freezer
at -10 ° C
No attempt is made to prevent moisture from condensing on a slab when it
is brought at room conditions
A mix of cement is made on the frozen / cold slab by adding the powder
until correct consistency is reached
The amount of powder incorporated with this technique is 50-70% more
than with the normal procedures
47. CONTROL OF WORKING TIME
The length of the working time may be varied to some degree to fit the clinical
situation. For eg. A fixed dental prosthetics with multiple crowns require more
working time for cementation. Four techniques can extend the working time of ZP
cement:-
1. P/L ratio can be reduced to produce a thinner mixture. This however, reduces
initial pH and adversely affect the properties.
2. Smaller portions of powder should be mixed for the first few increments. This
reduces the acidity of the liquid and retards the rate of reaction.
3. Prolong the spatulation of the last increment of the powder. This destroys the
matrix formed, thus extra time is needed to rebuild the bulk of the matrix. This
is however, not a preffered method for prolonging the working time.
48. CONTD.. CONTROL OF WORKING TIME
4. A cooler mixing temperature retards the chemical reaction between powder and the
liquid, thereby delay formation of matrix.
However, the temperature of the slab should be above the dew point,
otherwise water condenses, dilutes the liquid and reduces the compressive
and tensile strength of the cement.
This is the most feasible method of extending the working time of zinc
phosphate cement.
49. PROPERTIES OF ZINC PHOSPHATE
• Compressive Strength – 104 MPa
• Tensile Strength – 5.5 MPa
• Modulus of Elasticity – 13 GPa
• Solubility – 0.06% (relatively low)
• Thermal Properties – Good
• Adhesive Properties – No bond formation
• Biological Properties – starting pH: 3.5, at the time of
cementation, pH is: 2 and after 24hrs, pH is 5.5
• Optical Properties - Opaque
50. PRECAUTIONS
1. The liquid bottle should be kept closed when not in use to prevent
changes in water content.
polyethylene squeeze bottles don’t require removal of a dropper and thus eliminates the
tendency for gain or loss of water from liquid
2. Liquid should be dispensed onto the slab until mixing is to be initiated
because water will be lost by evaporation
3. A bottle which has become cloudy due to the loss of water should be
discarded.
Such a condition is the result of precipitation of buffering salts
Last 1/5th portion of the liquid should be discarded to ensure consistent mix
51. ZINC PHOSPHATE
ADVANTAGES
• Good compressive strength
• Can be used in regions of high
masticatory stress or long span
prosthesis.
• Good thermal insulation ability
• Does not dissolve in oral fluids
• Adequate film thickness
• Reasonable working time
DISADVANTAGES
• No chemical adhesion
• Pulp irritation
• Poor aesthetics
• Low tensile strength
no fluoride release
52. APPLICATIONS OF ZINC PHOSPHATE
• Luting for restorations
• High strength bases
• Temporary restoration
• Luting for orthodontic bands and brackets
53. MODIFICATIONS OF ZINC PHOSPHATE
CEMENT
I. Hydro Phosphate Cement
II. Copper Cement
III. Silver Cement
IV. Fluoride Cement
55. HYDRO PHOSPHATE CEMENT
• It is an innervation in the compounding of Zinc phosphate cement in the mixing of
dehydrated dihydrogen phosphates, zinc, calcium and other metals
As well as the oxides of these metals with water
• The properties like compressive strength, film thickness, solubility and disintegration
are somewhat inferior to that of Zinc Phosphate cement
• The acidity is similar to that of conventional Zinc Phosphate cement
• Used for luting and bases
57. COPPER CEMENT
Copper oxides are sometimes added to the powder of Zinc Phosphate
cement to increase their antiseptic properties
They can be combined directly to powder form with phosphoric acid to
produce cement
USES:
Temporary restoration particularly in pedodontics
Seldom used currently because their clinical behavior doesn’t seem to be superior to any
other temporary restoration and their toxic reaction to the pulp is generally recognized
58. COPPER CEMENT
Copper cements have been classified according to the percentage of
copper oxide that is used to replace zinc oxide
a) Type I: those in which up to 25% of copper oxide has been added to
replace zinc oxide (ZnO)
b) Type II: those in which copper oxide is present as an amount of 2-5%
60. SILVER CEMENT
Generally contain few percentage of salts such as AgPO4 (silver phosphate)
Silver salts darkened to silver sulfide on exposure in the mouth, hence used
only in posterior teeth
62. FLUORIDE CEMENT
Some Zinc Phosphate cements that contain a few percentage of stannous
or other fluorides are obtainable that may be suitable for orthodontic
cementation
They have a lower strength and higher solubility than Zinc Phosphate owing
to the dissolution of fluoride containing material
Fluoride uptake by enamel of some cements results in reduced enamel
solubility
71. SETTING REACTION
• Setting begins by dissolution of the powder particles by the acid, which
releases zinc, magnesium, and tin ions
• These bind and cross-link the carboxyl groups.
• The result is a cross-linked polycarboxylate matrix phase encapsulating
the unreacted portion of the particles
• The hardened zinc polycarboxylate cement is an amorphous gel matrix
in which unreacted powder particles are dispersed.
72. PROPERTIES
• Compressive strength = 55 MPa
• Tensile strength = 6.2 MPa, less brittle
• pH : rapidly rises from 3 to 6
• Pulpal response : mild
• Pulp protection : less irritation as the particle size and molecular weight is
higher and the acidic content is neutralized rapidly.
• Thermal insulator - good
73. PROPERTIES
• Solubility = 0.6 % - more soluble than zinc phosphate
– Marginal dissolution is more which increases in acids like lactic acid.
– Low P/L ratio increases the solubility
• Adhesion properties – micromechanical & chemical (carboxyl
group of tooth structure)
• Opaque
• Anticariogenic properties –less as compared to GIC.
74. MANIPULATION
CONDITIONING:
Tooth is cleaned for proper bonding
10% polyacrylic acid solution followed by rinsing with water or 1-3%
hydrogen peroxide may be used
Tooth is then dried and isolated
PROPORTIONING:
1.5 parts of powder to 1 part of liquid by weight
75. MANIPULATION
PROCEDURE:
• Powder and liquid are taken on a cooled glass slab
• Liquid is dispensed just prior to mixing
• Powder is incorporated into liquid in bulk (90%) with a stiff cement spatula
• Remaining powder is added to adjust consistency
Mixing time: 30-40 seconds
Setting time: 7-9 mins. (can be increased by cooling the glass slab)
76. MANIPULATION
• A proper mix of polycarboxylate cement is somewhat thicker in appearance
but has a shiny glossy appearance
• The glossy appearance indicates that polyacrylic acid is still available to
bond to the tooth structure
• The cement should be used at this stage
• Any delay causes loss of glossiness and formation of “cob-webbing” and it
should be discarded
• A proper mix forms a thin strand when lift up by the spatula
80. MANIPULATION
Notes:
1. Cement should be used while the surface is still glossy
Loss of luster indicates that the setting reaction has progressed to an extent that proper
wetting of the tooth surface by mix is no longer possible
2. After insertion, the excess isn’t removed immediately as it passes through
a rubbery stage, tends to get lifted from the cavity
Remove excess cement only when it hardens and breaks off.
3. The powder may be cooled, but the liquid shouldn’t be cooled since the
viscosity of liquid increases
81. ZINC POLYCARBOXYLATE CEMENT
ADVANTAGES
– Chemical bonding
– Good marginal adaptation to
tooth structure and metal alloys
– Mildly acidic
– Excellent biocompatibility with
pulp
– Easy manipulation
DISADVANTAGES
• Less compressive strength
• Poor esthetic
• Solubility is high
• Shorter mixing and working
time
• Need for clean surface to utilize
adhesion potential
• Anticariogenic properties not
good as GIC because fluoride
ion can’t leach out properly
82. NOTE ON ANHYDROUS ZINC
POLYCARBOXYLATE CEMENT
ZnPolyF cement is made available as single component system
That is single powder which is incorporated or later mixed with distilled water
In this system, the polyacrylic acid is freeze dried and powdered acid is
mixed with the traditional cement powder
The liquid for this material of water with pH of 4.2- 4.5 compared to pH of
10-16 for polycarboxylic acid
When this powder is mixed with water, the PAA goes into solution and the
setting reaction proceeds as in similar manner as conventional P/L system
85. ZINC OXIDE EUGENOL CEMENT
Zinc oxide eugenol (ZOE) cementhavebeen used extensively in dentistry
since 1890s.
They are cements of low strength.
Also they arethe least irritating of alldental cements and areknown to havean
obtundent effecton exposed dentin.
86. CLASSIFICATION
T
ypeI ZOE: For temporarycementation
Type II ZOE: PermanentCementation
T
ypeIII ZOE: Temporary fillingandthermal base
T
ypeIV ZOE: CavityLiners
88. COMMERCIAL NAMES
– Unmodified: Tempac – Type III, Cavitic – Type IV, Temp
bond – Type I
– EBA alumina modified: Opotow Alumina EBA – Type II
– Polymer modified: Fynal – Type II, IRM – Type III
89. SETTING REACTION
• In theFirst Step Hydrolysis of Zinc Oxide to its hydroxidetakesplace.
• Water isessentialfor the reaction,dehydratedzincoxide will not react with dehydrated
eugenol
ZnO + H2O →Zn(OH)2
The reactionproceedsasatypicalacid– basereaction unmodified
Zn (OH)2 + 2HE → ZnE2 +2H2O resin bonded ZnOE cement
(Zinc hydroxide) ( Eugenol)- (Zinc eugenolate )
The chelate formed is anamorphous gelthattends to:
• Crystallizeimparting strengthto theset mass.
• Structure ofsetcement: Itconsists of particlesofzincoxideembeddedina matrixofzinc eugenolate.
• Setting time:4-10mins.
90. SETTING REACTION
a) It involves chelation of 2 eugenol molecules with one zinc ion to form zinc
eugenolate
b) The set mass contains residual ZnO particles bonded by a matrix of zinc
eugenolate or some free or unreacted eugenol
c) Small amount of water is necessary to initiate the reaction between
eugenol and ZnO particles.
Water hydrates ZnO to form Zn(OH)2 which then serves as a source of zinc ions
d) Reaction is reversible because of zinc eugenolate is easily hydrolyzed by
moisture to eugenol and hydroxide
Then the cement disintegrated rapidly and exposed to oral conditions
91. MANIPULATION
Power – Liquid System
Powder/liquidratio:4:1-6:1wt.%
After shakingthebottles gently, measuredquantity ofpowder andliquidaredispensed onto a
cool glassslab.
The bulk ofthepowder isincorporated intotheliquidandsaturatedthoroughly in a circular
motion with a stiff bladedstainlesssteel spatula.
Smallerincrementsarethenaddeduntil themixis complete.
92. MANIPULATION
1. Proportioning: the powder bottle should be shaken well before
dispensing to get uniform composition. The powder is dispensed at 1 end
of the mixing slab/pad. There’s no need of incorporation of the powder
to small increments in the beginning since the reaction isn’t exothermic
and the pH is around 7.
Mixing: initiated by the addition of bulk increments. The mix is thoroughly spatulated and
then a series of smaller increments is added until a required consistency is achieved.
The correct mix can be rolled on a glass slab for restorative consistency.
2. Proportioning and mixing: more powder is required for cementing, i.e.
propagation. The powder is mixed with liquid in small portions with
vigorous spatulation until correct amount has been incorporated.
93. MANIPULATION
In order to obtain optimum properties, it is important to use as high powder
liquid ratio as possible, i.e. 3.59 gm/ml for cementation and 5-6 gm/ml for
liners and bases
The cement mixes readily to a very fluid consistency even at a higher P/L
ratio. Reverse spatulation is required for about 2 mins to incorporate all the
powder.
Because of the long working time, adequate setting time in the mouth
should be allowed.
96. FACTORS AFFECTING SETTING TIME
FACTORS To decrease setting time To increase setting time
1. P/L ratio High Low
2. Temp. of spatula
and mixing slab
Warm glass slab and spatula Cool spatula and glass slab
(provided the temp. not lower
than dew point)
3. Spatulation time Shorter Longer
4. Amount of water
(humidity)
High Low
5. Rate of powder
incorporation
Introduction of bulk quantity of
powder into liquid
Introduction of small quantity of
powder into liquid
97. COMPOSITION- UNMODIFIED ZnOE
POWDER Ingredients % Functions
1. ZnO (USP or arsenic free) 69% Reactive ingredient
2. White rosin or hydrogenated
resin
29.3% Reduces the brittleness of the set
cement
3. Zinc acetate 0.7% Serves as an accelerator by providing
zinc ions
4. Zinc stearate 1% Plasticizer
LIQUID Ingredients % Functions
1. Eugenol/oil of
cloves
85% For the reaction with zinc or reactive
ingredient
2. Olive oil/cotton
seed oil
15% Plasticizer and to control the viscosity
98. UNMODIFIED ZnOE
ADVANTAGES
Obtundent effects on the pulpal tissues
Good sealing ability
Resistance to marginal penetration
DISADVANTAGES
Solubility and disintegration in oral
fluids
No anti-cariogenic property
Lack of adhesion to the tooth structure
Low strength and abrasion resistance
99. USES
For temporary restoration (it has got good obtundent properties)
Temporary cementation of restoration
Cavity liners in deep cavity preparations
Pulpcappingagent
For temporary andpermanent cementation
Asabase
Secondaryuse– root canalrestorations.
101. COMPOSITION –EBA ALUMINA ZnOE
POWDER % FUNCTIONS
ZnO 64% Reactive ingredient
Hydrogenated rosin 6% To reduce the brittleness and film thickness and to
improve mixing qualities
Alumina / fused quartz 30% For strength or reinforcing filler to increase compressive
and shear strength
LIQUID % FUNCTIONS
Eugenol 37.5% • Reactive ingredient
O-EBA 62.5% • To improve the strength of the cement
• To promote the formation of a stronger
crystalline matrix
102. SETTING REACTION
For EBA alumina:
ZnO+ eugenol / EBA Eugenolate- 2- ethoxy benzoate
(matrix)
Reaction appears to involve chelate salt formation between EBA, eugenol
and zinc oxide
103. PROPERTIES
Thermal properties – theirthermalinsulatingpropertiesare excellent
Solubilityanddisintegration– The solubilityoftheset cementis highestamong
thecements(0.4% - wt.) theydisintegrate inoral fluids
Adhesion – theydo not adherewell to theenamelanddentin. This is one reason
whytheyarenot often used for final cementationofcrowns and bridges.
Biologicalproperties.
pH andeffecton pulp(pH is6.6to 8) theyaretheleastirritatingof allcements.Pulpal
responses are mild.
They havesoothingeffecton the pulp.
104. USES
Permanent cementation of restoration
Temporary restorations
Base / liner under restorative material (Eg.: amalgam, silicate,
silicophosphate, GIC)
For sealing coronal portion of tooth undergoing endodontic treatment
105. EBA ALUMINA ZnOE
ADVANTAGES
• Long working time
• Easy manipulation
• Good flow and strength
characteristics
• Low irritation to the pulp
DISADVANTAGES
• Critical proportioning i.e. higher
powder-liquid ratio for optimum
properties
• Hydrolytic breakdown in oral fluids
• Liability to plastic deformation (poor
retention) than ZnPO4 cement
106. RESIN REINFORCED ZINC OXIDE
EUGENOL CEMENT
Reinforcing polymer incorporated into the powder
It gives the cement strength to resist condensation forces and to ensure
adequate life when used as a temporary restorative material
Reinforcing material is incorporated in the powder instead of liquid, so the
mixing properties are excellent
Though it is reinforced, can be removed easily when used as temporary
material
107. COMPOSITION – RESIN BONDED ZnOE
POWDER % FUNCTIONS
ZnO 90% Main reactive ingredient
Finely divided natural or
synthetic resins such as
polystyrene or PMMA
Some acidic resins such as
colophony etc.
10% To improve the strength of the set cement
LIQUID % FUNCTIONS
Eugenol 85% Main reactive ingredient
Olive oil 14% Plasticizer and controls the viscosity as well
Acetic acid Traces As an accelerator
Thymol or 8-hydroxy
quinolone
Traces Antimicrobial agent
108. SETTING REACTION
Similar to that of ZnOE cements
Acidic resins if present, might react with ZnO
Strengthens the matrix
109. MANIPULATION
• Powder and liquid dispensed on a dry glass slab
• 50% of powder is mixed into liquid and remaining in small parts with
vigorous spatulation
• Mix appears stiff, which improves the plasticity after additional 5-10 seconds
mixing
• Working time: long
• Setting time: 6-10 mins (sets faster in mouth due to heat and moisture)
110. PROPERTIES
Compressive strength 48 MPa (7000 psi)
Tensile strength 4.1 MPa (600 psi)
Modulus of elasticity 2.5 GPa
Film thickness 32 μm
Solubility and disintegration 0.03% wt.
Pulp response Moderate: similar to unmodified ZOE
Abrasion resistance and toughness Improved
111. USES
Permanent cementation
Luting agent for restoration
As cavity liners
As intermediate or temporary restorations
112. CONTRAINDICATIONS
As with other Eugenol containing materials, the polymerization of acrylic
direct filling materials (acrylic resins and composite resins) and temporary
crown and bridge materials is inhibited and use with these materials must be
avoided
113. RESIN BONDED ZnOE
ADVANTAGES
Adequate strength for final
cementation of restoration
Good obtundent effect or minimal
reaction to pulp
Good initial sealing properties
Easy manipulation
DISADVANTAGES
Minimal mechanical properties for
luting i.e. lower strength, higher
solubility and disintegration than
ZnPO4 cement
Hydrolytic breakdown when
exposed to oral conditions
Softening and discoloration of some
resin restorative materials
116. VANILLATE AND SYRINGATE CEMENTS
Recently cements have been developed containing hexyl vanillate and ortho ethoxy
benzoic acid (O-EBA)
HV-OEBA as a substitute for eugenol
This liquid is mixed with zinc oxide (ZnO) powder
Dispensing: powder-liquid system
Components:
Powder: ZnO (64%), Al2O3 (30%), Hydrogenated rosin (6%)
Liquid: EBA (87.5%), n-hexyl vanillate (2.5%)
These cements have high strength and low solubility, and are suitable for patients
sensitive to eugenol
117. SPECIAL ZnOE PRODUCT (ROOT CANAL
SEALERS)
Modification of ZnOE cavity lining materials
These pastes can be used alone or in combination with gutta percha or
silver points
This material contains :
• Antibiotics eg.: Tetracylines, Steroids, Disinfectants (para-formaldehyde),
radio-opacifiers (BaSO4, BiO2)
124. PROPERTIES
Pulpal response: positive control severe irritant
Setting time: 3 mins-9 mins
Compressive strength: 167 Mpa
Tensile strength: 15 MPa
Solubility: ADA: <1% and commercial product: 0.7%
Surface hardness: 70 KHN (knoop hardness number)
Acidity (pH at 2 mins): 2.8
125. SILICATE CEMENTS
MERITS
• Anticariogenic property or ability to
prevent marginal caries
• Good initial aesthetics
• Good compressive strength
DEMERITS
• Severe irritant to pulp
• Readily soluble in oral fluids
• Brittleness
• Low resistance to impact, stress and abrasion
• Moisture sensitivity
• Lack of color stability
• Lack of adhesive bonding to the tooth structure
126. SILICATE CEMENTS
INDICATIONS
• Class III anterior restoration
• For patient having high caries
index; i.e. rampant caries
• As an intermediate restorations
CONTAINDICATIONS
• Class II cavities in posterior teeth
• Biting edges of anterior teeth
• For mouth breathers
133. PROPERTIES
Pulpal response: greater potential
for pulpal irritation
Compressive strength:
Type I: 140 MPa
Type II: 170 MPa
Tensile strength: 71 MPa
Solubility:
Type I: 1.5%
Type II: 1.0%
Surface hardness: 70 KHN
134. SILICOPHOSPHATE CEMENT
MERITS
• Higher strength
• High abrasion resistance
• Higher toughness than Zn3(PO4)2
• Lower solubility
• Degree of translucency
DEMERITS
• Greater potential for pulpal irritation
• Less satisfactory mixing and
rheological property
• Higher film thickness
135. SILICOPHOSPHATE CEMENT
INDICATIONS
• Cementation of fixed restorations esp. porcelain due
to their translucency
• Cementation of orthodontic bands because of less
decalcification in adjacent tooth enamel
• Temporary posterior restoration, intermediate and
deciduous restoration
• As die materials (positive reproduction of prepared
tooth)
CONTRAINDICATIONS
• Permanent restoration
136. NOTE ON ANTI-CARIOGENIC PROPERTY
It is due to the release of fluoride from restoration
These ions are responsible for decreasing the chance of decay of adjacent
tooth
Fluoride ion will be released throughout the life of the restoration
Fluoride leaching from the cement acts as an anticariogenic agent.
137. PHYSIOCHEMICAL MECHANISM OF CARIES
Fluoride ion released during the setting and subsequent dissolution of
silicate cement reacts with the adjacent tooth to form a structure that is more
resistant to acid decalcification and reduces enamel solubility
The surface energy of fluorapatite is lower than hydroxyapatite making the
adhesion of unwanted cariogenic substance such as dental plaque more
difficult
Release of fluoride ion in low concentration contributes to the formation of
acid resistant crystal.
140. RESIN CEMENTS
• Based on methyl methacrylate, have been used since 1952 for cementation
of inlays, crowns etc.
• Developed with the development of composite resins
• They are low viscosity flowable composites
141. APPLICATIONS
To bond orthodontic brackets to acid-etched enamel
Cementation of porcelain veneers and inlays
Cementation of all-porcelain crowns and FPDs
Cementation of etched cast restorations
143. RESIN CEMENTS
Chemically activated resins: used for all types of restoration
Light activated resins: can’t be used in all situations because of problems in
light penetration
Dual cure resins: used when the material being bonded allows some
degree of light penetration
The areas where light cannot penetrate cure subsequently by chemical reaction
144.
145. SUPPLIED AS
Chemical cured:
2 paste system containing base and accelerator
Single paste system with activator in the bonding liquid
Light cured: single paste system
Most systems include a bonding agent and etchant
Commercial names: Panavia F, Infinity, Resilute (Pulpdent), Transbond
XT(3M), Maxcem Elite (Kerr), Variolink Esthetic (Ivoclar)
147. PROPERTIES
Compressive strength 180 MPa (26000 Psi)
Tensile strength 30 MPa (4000 Psi)
Film thickness 10-25 μm
Biological properties Pulp irritant. Pulp protection with Ca(OH)2 or
GIC liner in the areas near to pulp
Solubility Insoluble in oral fluids
Polymerization shrinkage High
Adhesion properties Do not adhere to tooth structure, may lead to
microleakage if used without etching and
bonding
Bond strength to enamel 7.4 MPa (1070 Psi). Usually stronger with
enamel.
148. POLYMERIZATION
I. Chemically by peroxide-amine system
II. By light activation
III. By both chemical and light activation (dual cure)
150. ETCHING THE RESTORATION
Etching metal:
• Metal surface can be etched or roughened by blasting 30-50 μm alumina to
improve retention
• Etching is more effective
• Process is carried out in a electrolyte bath containing an acid like sulfuric
acid-also known as electrochemical etching
• Silica coating can be used to improve bonding
151. RESIN CEMENTS
Etching porcelain:
• Ceramic is highly inert material and is immune to attack by most acids
• Can be etched by using hydrofluoric acid
• Esthetic surfaces are protected with coating of wax.
152. RESIN CEMENTS
Orthodontic brackets:
A fine mesh on the bonding side of bracket helps to improve its retention
Cement flows into the mesh and locks to provide good mechanical retention
Coating with organosilane improves bond strength.
153. BONDING AND CURING
Chemically activated systems:
2 paste systems: 2 components are combined by mixing on a paper pad
for 20-30 seconds
Single paste system with activator in bonding agent: the activator is
present in bonding agent
Bonding agent is painted on the etched surface and restoration
Setting occurs when the cement on the restoration contacts bonding agent on tooth
154. DUAL CURE SYSTEM
2 components are mixed and light cured
Exposure time should never be <40 seconds
Light curing gives high initial strength
Light curing polymerizes the exposed cement at the margins of the
restoration which is affected by air inhibition
155. REMOVAL OF EXCESS CEMENT
• Excess cement removal is critical
• Removal can be very difficult due to strength of the material
• Should be attempted soon after seating before the material has hardened
• Some manufacturers recommend a partial light cure to facilitate removal
followed by completion of curing
158. COMPOMERS
Compomers / poly acid modified composites are used for restorations in low
stress bearing areas
Recent product is recommended by manufacturer for class I and class II
restorations in adults
Recommended for patients at medium risk of developing caries
159. COMPOSITION AND SETTING REACTION
Contain poly acid-modified monomers with fluoride-releasing silicate glasses
Formulated without water
Some compomers have modified monomers that provide additional fluoride release
Volume % filler ranges from 42%-67%
Average filler particle size: 0.8 to 50 μm
Available as: single paste packaged in compules and syringes
160. COMPOSITION AND SETTING REACTION
• Setting occurs by light-cured polymerization
• But an acid-base reaction also occurs as the compomer absorbs water after
placement and upon contact with saliva
• Water uptake is also important for fluoride transfer
161. PROPERTIES
Release fluoride by mechanism similar to that of glass and hybrid ionomers
Because of lower amount of glass present in compomer, the amount of
fluoride release and its duration are lower than those of glass and hybrid
ionomers
They do not recharge from fluoride treatment or brushing with fluoride
dentifrices / toothpastes as much as glass and hybrid ionomers
163. MANIPULATION
• Packaged in unit-dose compules
• They require a bonding agent to bond to tooth structure
164. REFERENCES
1. Philips’ science of dental materials (1st South Asia Edition)
2. Craig’s restorative dental materials (12th edition)
165. QUESTIONS
LONG QUESTIONS:
1. Classify dental cements. Write the composition, uses and properties of
Zinc Phosphate Cement (15 marks)
2. Classify dental cements. Write in detail about Zinc oxide eugenol cement.
3. List the luting cements. Write in detail about polycarboxylate cement.
166. QUESTIONS
WRITE SHORT NOTES ON: (5 marks each)
1. Anticariogenic properties of a restorative material
2. Properties of Zinc Phosphate Cement
3. Write in brief the properties, advantages and disadvantages of Zinc Phosphate
Cement / ZnOE
4. Low strength bases
5. Calcium hydroxide
6. Zinc Oxide Eugenol paste
7. Anticariogenic property of silicate cement
8. Properties of ZnPO4 cement / ZnOE
167. QUESTIONS
WRITE SHORT NOTES ON: (5 marks each)
1. Composition and setting reaction of ZnOE paste
2. Uses of varnish
3. Zinc Phosphate Cement
4. Dental varnish
5. Dual cure and tri-cure system
