Dental Cements

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DENTAL CEMENTS

Dr. Nithin Mathew

CONTENTS

• Glossary• Introduction• History• Classification• Ideal requirements of Dental Cements• Phosphate Based Cements

• Zinc Phosphate Cement• Modified Zinc Phosphate Cement• Silicophosphate Cement

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• Phenolate Based Cements• Zinc oxide Eugenol cement• Reinforced Zinc oxide eugenol cement• EBA modified phosphate cement• Calcium Hydroxide Cement

• Polycarboxylate Based Cements• Zinc Polycarboxylate• Glass Ionomer cements

Dental Cements - Dr. Nithin Mathew

• Polymer Based Cements• Acrylic resin cement• Adhesive resin cement• Dimethacrylate cement

• Agents for pulp protection• Cavity varnish• Cavity liner• Cavity base

• Conclusion• References

4Dental Cements - Dr. Nithin Mathew

GLOSSARY

ACID – BASE REACTION

Chemical reaction between a compound with replaceable hydrogen ions (acid) and asubstance with replaceable hydroxide ions (base) that yields salt and water.

BASE

A material that is used to protect the pulp in a prepared cavity by providing thermalinsulation.

FILM THICKNESS

According to ADA/ANSI Sp. No. 96, it is the thickness in micrometers of set cement10minutes after a load of 150N has applied by a flat plate against another flat surface.


LUTING AGENT

A viscous cement-like material that fills the gap between bonded materials

SETTING TIME

The time elapsed from the start of mixing to the time at which the setting reactionessentially stops as measured by reaching a desired hardness or consistency.

WORKING TIME

The elapsed time from the start of mixing to the time at which the consistency of amaterial is no longer suitable for its intended use or a rapid rise in viscosity occurs.


INTRODUCTION

• Dental cements have been in use in dentistry for a very long time.

• They serve several purposes such as retaining restorations and prosthesis in the mouth.

• Also restorative, endodontic, orthodontic, periodontic as well as surgical procedures.

• Last 2 decades have seen a variety of changes in the dental cement composition and alsointroduction of newer advanced biocompatible materials.


• Definition:• A substance that hardens from a viscous state to a solid state to join 2 surfaces.

• In dentistry, A cement acts as a base, liner, filling material or adhesive to binddevices and prosthesis to tooth surfaces or to each other.


HISTORY

• First used dental cement- silicate cement

• 1871- Silicate cements (Fletcher)

• 1879- Zinc phosphate cements (Otto Hoffman)

• 1920- Calcium hydroxide (Hermann)

• 1942- Zinc oxide eugenol (Chrisholm)

• 1947- Methyl methacrylate resins

• 1960- Composites

• 1972- Glass Ionomers (Wilson & Kent)


CLASSIFICATION

• Based on the INGREDIENTS

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WATER BASEDGlass & Resin Modified Glass Ionomer

Zinc PolycarboxylateZinc Phosphate

OIL BASEDZinc oxide eugenol

Non-eugenol Zinc oxide

RESIN BASEDComposite and Adhesive Resins

Compomer


• According to O’Brien (by Matrix type):

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PHOSPHATEZinc Phosphate

Zinc Silico phosphate

PHENOLATEZinc oxide eugenol

Calcium Hydroxide Salicylate

POLYCARBOXYLATEZinc Polycarboxylate

Glass Ionomer

RESINPolymethy MethacrylateDimethyl Methacrylate

Adhesive

RESIN MODIFIED GLASS IONOMERHybrid Ionomer


• According to Phillip’s:

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Cement Primary Use Secondary Use

ZnPO4 • Luting agent for restoration and orthodontic bands

• Intermediate restorations• Thermal insulating bases• Root canal restorations

ZnPO4 With Silver & Copper Salts

• Intermediate restorations

Copper Phosphate • Temporary and intermediate restorations

ZOE • Temporary and intermediate restorations

• Luting agent • Thermal insulating bases• Pulp capping agents

• Root canal restorations• Periodontic bandage

Poly Carboxylate • Luting agent • Thermal insulating bases

• Luting agent for orthodontic bands

• Intermediate restorationsDental Cements - Dr. Nithin Mathew

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Cement Primary Use Secondary Use

Silicate • Anterior fillings

Silicophosphates • Luting agent for restoration • Intermediate restorations• Luting agent for orthodontic

appliancesGIC • Coating for eroded areas

• Luting agent for restoration • Pit &fissure sealants• Anterior restorations• Thermal insulating bases

Resin • Luting agent • Temporary restorations

Ca(OH) 2 • Thermal insulating bases• Pulp capping agents


• According to Craig:

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Functions Cements

Final cementation of completed restorations ZnPO4, zinc silicophosphatesReinforced ZOE,Zinc poly carboxylate ,GIC

Temporary cementation of completed restorations/cementation of temporary restorations

ZOE,Non eugenol zinc oxide

High strength bases ZnPO4, Reinforced ZOE, Zinc poly carboxylate, GIC

Temporary fillings ZOE, Reinforced ZOE, Zinc poly carboxylateLow strength bases ZOE, Ca(OH) 2

Liners Ca(OH) 2 in a suspensionVarnishes Resin in a solvent


• According to Coombe:

• According to ADA Specification:

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• Acid base reaction cements• Polymerising materials

Cyano acrylatesDimethacrylate polymersPolymer ceramic composites

Type I - Fine grain for cementation, luting

Type II - Medium grain for bases, orthodontic purpose


• According to Donovan:

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Conventional CementsZinc Phosphate

Zinc oxide eugenolZinc polycarboxylate

Glass Ionomers

Contemporary CementsResin Modified GIC

Resin Cements


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USE CEMENT TYPE

Luting inlays, crown, posts, multiretainers, FPD GICHybrid ionomersDual cure resins

Nonvital teeth with advanced pulpal recession and average retention

ZnPO4

Vital teeth with average retention, average pulpal recession, thin dentin, especially for single unit and small span FPD

Zn poly carboxylate

Multiretainer splints on vital teeth with above average retention, minimal dentin thickness, hypersensitive patients

Zinc oxide eugenol polymer based


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USE CEMENT TYPE

Provisional cementation Zinc oxide eugenolZinc poly carboxylate

Provisional cementation and stabilization of old ,loose restorations, fixation of facings and acid etched cast restorations

Dimethyl resin composites

Base/linerCavity with remaining dentin thickness greater than 0.5mm

Cavity with minimal dentin or exposure

GIC,resin ionomerZinc poly carboxylateZinc phosphate Calcium hydroxide salicylateZinc oxide eugenol polymer


IDEAL REQUIREMENTS

• Non-toxic, Non-irritant to pulp and tissues

• Insoluble

• Mechanical properties

• Adhesion to enamel and dentin

• Bacteriostatic

• Obtundant effect on pulp

• Thermal, chemical and electrical insulation

• Optical properties


CHARACTERISTIC PROPERTIES OF DENTAL CEMENTS

FILM THICKNESS & CONSISTENCY

Height of space between two surfaces separated by cementEg:distance between tooth surface and cemented crown

• Determines the adaptability and retention of restoration

• Consistency of the cement should be thick and plastic enough for ease of handling andplacement into the cavity

• Heavier the consistency Greater the film thickness Less complete seating of restoration


• Maximum allowable film thickness• For luting application : 20-25 µm• For restorative application -temporary/final cementation : 40 µm

• Ultimate film thickness depends up on the• Particle size of the powder• Concentration of the powder in liquid• Viscosity of liquid• Consistency of cement• Amount of force


VISCOCITY

Resistance of a liquid to flow

• It is a measure of consistency

• Factors affecting viscosity• Increase in temperature and time - increase the viscosity of certain cements


SETTING TIME

The elapsed time from the start of mixing to the point at which the mixture reaches adesired hardness or consistency

Net setting time:

Time elapsed between the end of the mixing and the time of setting

Working time:

Elapsed time from the start of mixing to the point at which the consistency of thematerial is no longer suitable for its intended use


STRENGTH

• ANSI /ADA specification recomends that the standard luting consistency of dental cementmust exhibit a minimum 24 hr compressive strength of 70 Mpa

SOLUBILITY• Solubility in oral fluids & water• Water based cements are more soluble than resin or oil-based cements• Decrease in P:L ratio : higher solubility and disintegration rate

• ADA - 0.2Wt%

• Maximum permissible rates of dissolution• GIC : 0.1 wt%• Zinc Phosphate : 0.2 wt%• Zinc Polycarboxylate : 0.3 wt%


REMAINING DENTIN THICKNESS

• Type of material to be used depends upon the minimum thicknessof the dentin left between the pulp floor and the dental pulp –Remaining Dentin Thickness (RDT)

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• RDT ≥ 2mm :• Cavity Liner only to be given on all internal

surfaces (for metallic restorations)

• No liners or base for GIC or Composite


• RDT < 2mm :• Base must be given on the pulpal and axial floor

(0.5 – 0.75mm)

• RDT < 1mm :• Cavity Liner is given on all internal surfaces, over which

a Base is given.


LUTING MECHANISM

• By Schillinburg

• Non-Adhesive:• Cement fills the restoration-tooth gap and holds by engaging in small surface

irregularities

• Micromechanical Bonding:• Surface irregularities are enhanced by air abrasion or acid etching• Improves the frictional retention

• Molecular Bonding:• Chemical bond formation between cement and the tooth structure



ZINC PHOSPHATE CEMENT

• Introduced by Dr. Otto Hoffman during the 1800s

• One of the oldest cement

• Acts as the gold standard by which newer materials are compared.

APPLICATION

• Luting of restorations

• Luting of orthodontic bands

• High strength bases


COMPOSITION

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POWDER % Function

ZnO 90.2% Principle ingredient

MgO 8.2% Reduce temperature of calcination process

SiO2 1.4% Improves the working characteristics

Bi2O3 0.1% Smoothness of mix &lengthen working time

Misc- BaO, Ba2SO4 & CaO 0.1%

LIQUID

H3 PO4 38.2% Reacts with ZnO

Al 2.5% Essential for cement forming reaction

Zn 7.1% Moderator for reaction between powder& liquid, allows adequate working time

H20 36% Controls the rate of reation


TYPES

• Type I – Fine Grained : (Film Thickness less than 25µm)• Luting permanent metallic restorations• Cementation of orthodontic bands

• Type II – Medium Grained : (Film Thickness of 40µm)• High strength thermal insulating base


• Exothermic reaction.

• The final set cement is a cored structure consisting primarily of unreacted zinc oxideparticles embedded in a cohesive amorphous matrix of zinc aluminophosphate.

3ZnO + 2H3PO4 + H2O Zn3(PO4)2.4H20

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SETTING REACTION

• Phosphoric acid attacks the surface of the particles

• Releases zinc ions into the liquid

• Aluminium forms complexes with phosphoric acid, reactswith zinc forming zinc aluminophosphate gel.


MANIPULATION

• P:L ratio of 1.4g : 0.5ml

• Amount of powder that can be incorporated into a given quantity of the liquid greatlydetermines the properties of the mixed mass of the cement.

• This is because increase in P:L ratio generally provides more desirable properties.

• Powder is dispensed onto the glass slab

• Divided into 4 – 6 increments.


• Powder is incrementally incorporated into the liquid

• Spatulated over a large area to dissipate heat produced during thereaction.• Powder quantity being minimal, heat generated is less• Helps to achieve slow neutralization of the liquid and better

control of setting reaction

• During middle of mixing, larger portions are added to furthersaturate the liquid.

• Finally, smaller increments are added to get the desired consistency.

• Each increment is spatulated for 15-20secs.

• Total mixing time is 60 – 90 secs.34Dental Cements - Dr. Nithin Mathew

Frozen Glass slab Technique:• To prolong working time and shorten setting time.• Glass slab cooled at 6°C or – 10°C.• 50 – 75% more powder incorporation.• Working time is increased by 4 – 11 mins• Setting time shortened by 20 – 40%

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Mixing time 1.5 – 2mins (Phillips)Working time 5mins (Phillips)Setting time 5-9mins (Craig)

5-14mins (O’Brien)Film thickness 20µm


MECHANICAL PROPERTIES

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Compressive Strength 104 MpaTensile Strength 5.5 MpaElastic Modulus 13.5 GpaSolubility in water 0.06 wt%Thermal conductivity 0.0028°C/cm


FACTORS AFFECTING SETTING TIME

• P:L ratio• Reducing the P:L ratio increases the working time and setting time

• Low initial pH which will impair the mechanical properties

• Smaller increments mixed for first few increments

• Prolonging the spatulation time

• Temperature of the mixing slab


BIOLOGIC PROPERTIES

• Freshly mixed ZnPO4 - highly acidic pH - pulpal irritation

• Very thin mixes must be avoided as it can be highly acidic.

• Pulp protection : High P:L ration must be used, Calcium hydroxide or cavity varnish.

• ADHESION : By mechanical interlocking of the set cement with cavity surface roughness

• Acts as a good thermal insulator.


MODIFIED ZINC PHOSPHATE CEMENT

COPPER & SILVER CEMENTS• Black copper cements : Cupric oxide• Red copper cements : Cuprous oxide

• Depending on the type of copper cement, concentration of the copper varies between 2%and 97%.

• Lower P:L ratio – for satisfactory manipulation characteristics• Highly acidic• Higher solubility• Lower strength than ZnPO4

• Less anticariogenic property

• Silver cements : contain small percentage of salts of silver phosphate



FLUORIDE CEMENTS

• Stannous fluoride (1-3%)

• Higher solubility and lower strength – due to dissolution of Fluoride

• Fluoride uptake by enamel : Reduced enamel solubility and Anticariogenic



SILICOPHOSPHATE CEMENTS (ADA Sp. No. 96)

• Presence of silicate glass: translucency, improved strength, fluoride release.

APPLICATIONS

• Type I : Cementation of fixed restorations

• Type II : Provisional restorative material

• Type III : Dual purpose material


COMPOSITION

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POWDER % Function

ZnO 10 -20 Principle ingredient

Silicate glass

Fluoride 12 – 25

Mercury / Silver Compounds Germicidal

LIQUID

Orthophosphoric acid Reacts with ZnO

Al salts 2 – 5

Water 45


PROPERTIES

BIOLOGIC EFFECT

• Prolonged low pH (4-5)

• Pulpal protection necessary

• Anticariogenic – fluoride release

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Working time 4 minsSetting time 5 – 7 minsCompressive Strength 140 - 170 MpaTensile Strength 7 MpaSolubility 1 wt%Toughness/Abrasion resistane Higher than phosphate cements


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ADVANTAGES DISADVANTAGES

Better strength, toughness, abrasion resistance, fluoride release, translucency

Total acidity greater than zinc phosphate

Better bonding than zinc phosphate High solubility



ZINC OXIDE EUGENOL (ADA SP. NO. 30)

• Introduced by Chrisholm in 1873

• Commonly used for luting and intermediate restorations

• Obtundant property on exposed dentin

APPLICATION

• Longterm and short-term luting agents

• Temporary and intermediate restorations

• Root canal sealers

• Surgical packs


TYPES (ADA Specification No. 30)

• Type I : Temporary restorations

• Type II : Permanent cementation of restorations

• Type III : Temporary restoration, thermal insulating bases

• Type IV : Cavity Liner


Dispensed As:• Two pastes• Powder and liquid

COMPOSITION

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POWDER % Function

ZnO 69 Principal component

White rosin 29.3 Reduce brittleness of the cement

Zinc stearate 1 Accelerator, plasticizer

Zinc acetate 0.7 Improves strength of the cement

Silica Filler

LIQUID

Eugenol / oil of cloves 85

Olive oil 15 PlasticizerDental Cements - Dr. Nithin Mathew

SETTING REACTION

• Hydrolysis of the ZnO

• Zinc hydroxide reacts with acid eugenol forming zinc eugenolate which crystalizes andstrengthens the cement

• Set cement also contains free zinc oxide embedded in a matrix of zinc eugenolate

• Reaction is reversible, zinc eugenolate can easily be hydrolysed by moisture in the oralcavity to eugenol and zinc hydroxide

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ZnO + H2O Zn(OH)2

Zn(OH)2 + 2HE ZnE2 + 2H20


MANIPULATION

• P:L = 3:1 / 4:1 (maximum strength)

• Powder and liquid are dispensed onto the glass slab.

• Zinc oxide is incorporated into the liquid

• Prolonged vigorous spatulation in circular motion isrequired with a stiff bladed stainless steel spatula.

• Larger increments are incorporated first and then smallerincrements until desired consistency is obtained.

• More powder is added to the mix, more stronger is thecement and more viscous the mixed cement.


PROPERTIES

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Base / Filling material

Temporary cement

Permanent cement

Cavity liner

Film Thickness (µm) 40 25

Setting Time (mins) 2 – 10 4 – 10 4 – 10 4 – 10

Solubility (wt%) 2.5 1.5

Compressive strength (Mpa) 25 35 35 5.5

Tensile strength (Mpa) 1 – 2 1 – 2 1 – 2 1 – 2

Thermal diffusivity 0.38 mm2/s

Linear COTE 35 x 10-6/°C


BIOLOGIC EFFECTS

• Bacteriostatic

• Obtundant property

• pH (6.6 – 8) : mild pulpal response

• Volumetric shrinkage : 0.9%

• When in direct contact with connective tissues, it is an irritant

• Reparative dentin formation in exposed pulp is variable


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Obtundant effect on pulpal tissues Low strength and low abrasion resistance

Good sealing ability Microleakage

Resistance to marginal penetration Disintegration in oral fluids

Good thermal insulation Less anticariogenic

Solubility is highest among all cements


REINFORCED ZINC OXIDE EUGENOL CEMENT

To overcome the shortcomings of the zinc oxide cements

APPLICATION

• Cementing crowns and FPD

• Cavity liner

• Base materials

• Provisional restoration


COMPOSITION

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POWDER %

ZnO

Finely divided natural / synthetic resin 10 – 40

Accelerators

LIQUID

Eugenol

Dissolved resins

Accelerators : Acetic Acid

Antimicrobial agents : thymol / 8-hydroxyquinolone


SETTING REACTION

• Similar to ZnO eugenol

• Acidic resin such as colophony may react with zinc oxide, strengthening the matrix

MANIPULATION

• (Method similar to ZnO eugenol)

• More powder is required for cementing mix

• Proper P:L ratio must be followed for adequate strength properties

• Mixing pad/slab should be completely dry


PROPERTIES

• Solubility is lower than ZnO eugenol cement due to the presence of resin

BIOLOGIC EFFECTS

• Inflammatory reaction in the connective tissue is present

• Softening and discoloration of the resin material57

Setting time 7 - 9 minsFilm Thickness 35 – 75 µmCompressive Strength 35 - 55 MpaTensile Strength 5 - 8 MpaModulus of elasticity 2 – 3 GpaSolubility 1 wt%


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Minimal biologic effects Low strength

Good initial sealing ability Higher disintegration

Adequate strength for final cementation of restoration

Softening and discoloration


EBA MODIFIED ZINC OXIDE EUGENOL CEMENT

APPLICATION• Cementation of inlays, crowns, FPD’s and for provisional restoration• Base / lining material

COMPOSITION

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POWDER %

ZnO 60 – 75

Aluminium oxide 20 – 35

PMMA 6

LIQUID

Eugenol 37

EBA 63Dental Cements - Dr. Nithin Mathew

SETTING REACTION• Not fully known• Appears to form chelate salt between EBA, eugenol and zinc oxide.

MANIPULATION• Similar to ZnO eugenol• Cement mixes readily to very fluid consistency even at a high P:L ratio• For optimal properties : use high P:L ratio as possible

• 3.5 g/ml : cementation• 5 – 6 g/ml : liners and bases

• Vigorous spatulation is required for about 2 mins to incorporate all of the powder


PROPERTIES

BIOLOGIC EFFECTS

• Similar to ZnO eugenol cement

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Setting time 7 - 13 minsFilm Thickness 40 - 60 µmCompressive Strength 55 - 70 MpaTensile Strength 3 - 6 MpaModulus of elasticity 5 GpaSolubility 1 wt%Plastic deformation 0.1mm/min at 37°C


CALCIUM HYDROXIDE

• Hermann – 1920

• Useful water setting cement which has osteoconductive and osteoinductive property

• As a pulp capping agent facilitates formation of reparative dentin – alkaline pH ,antibacterial and protein lyzing property.

TYPES:• Non setting (pH : 11 – 13) – intracanal medicament• Setting (pH : 9 – 10) – cavity liner


APPLICATION• Liners in deep cavity preparations• Intracanal medicaments• Direct and indirect pulp capping• Apexification procedures

COMPOSITION• 2 Pastes – Base and Catalyst

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BASE

Calcium tungstate / Barium sulphate Radio-opacifier

Tribasic calcium phosphate

Zinc oxide

Glycol salicylate


SETTING REACTION

• Calcium hydroxide reacts with the salicylate forming a chelate, amorphous calciumdisalicylate.

• Hydroxyl ions from the cement neutralize the acids produced from the clast cells and createan optimum pH for pyrophosphatase activity necessary for mineralization.

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CATALYST

Calcium hydroxide

ZnO

Zn Stearate

Ethylene Toluene


MANIPULATION

• Equal lengths of the 2 pastes are mixed to a uniform color

PROPERTIES

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Working time 3 – 5 mins (depends on availability of moisture1 – 2 mins (rapid)

Compressive Strength At 7 mins : 6MPaAt 1 hr : 10MPaAt 24hrs : 14-20MPa

Tensile Strength At 7 mins : 1.5MPaAt 1 hr : 1.5MPaAt 24hrs : 1.7-2MPa


• Solubility in 50% phosphoric acid during etching procedures is significant.

• Subject to Hydrolytic Breakdown : marginal leakage and finally complete dissolution of thelining occurs


BIOLOGIC EFFECTS

• Strong Antibacterial Action

• Ionic dissociation of calcium hydroxide into calcium ions and hydroxyl ions.(54.11% and 45.89% respectively)

• Hydroxyl ions induces chemical injury on the organic components of thecytoplasmic membrane of the bacteria, causing destruction of phospholipids orunsaturated fatty acids.


• Dentin Bridge Formation (Pulp Capping)

• Activates enzymes such as alkaline phoshphatase which is responsible formineralization

• Free calcium hydroxide helps in remineralization of carious dentin


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Easy manipulation Low strength even when fully set

Rapidly harden in thin layers Exhibit plastic deformation

Good sealing ability Dissolve under acidic conditions

Beneficial effects on carious dentin and exposed pulp


LIGHT ACTIVATED CALCIUM HYDROXIDE

• Recently introduced cement

COMPOSITION

• They have longer working time

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Calcium Hydroxide

Barium sulphate Radio-opacifier

Urethane dimethacrylate

HEMA

Activators – camphorquinone


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ADVANTAGES

Less brittle than conventional 2 paste systemImproved strength

No solubility in acids

Minimal solubility in water

Longer working time


DYCAL

• Introduced in 1979

• As a liner/pulp capping agent in deep cavities

• Radio-opaque calcium hydroxide which is self setting

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ADVANTAGES DISADVANTAGESHigh early strength

Lower water solubility

Excellent handling characteristics


CALYXL

• Calcium hydroxide containing sodium and potassium salts

• Allows maintenance of normal dentinogenesis by protecting the pulp against irritation fromoperative procedures



SILICATE CEMENTS (ADA SP. NO. 96)

• Fletcher in 1871

• Oldest direct tooth colored materials

• Steenbock later introduced an improved version of the cement

COMPOSITION

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POWDER LIQUID

Silicon Dioxide 35 – 50% Phosphoric acid

Sodium fluoride Sodium & Aluminium phosphate

Calcium fluoride

Aluminium fluoride

Aluminium trioxide

Sodium fluorideDental Cements - Dr. Nithin Mathew

SETTING REACTION

• Acid – Base Reaction• Powder particles are attacked by acid releasing Calcium, aluminium and fluoride ions.

• These ions precipitate as phosphates which form continuous cement matrix along with andforms a silica gel.

• Fluoride ions donot take part in this reaction. Present as free ions.

• Most of the powder particles are not dissolved, only the surfaces are dissolved.

• Finally the set cement contains a phosphate matrix containing unreacted powder particlessurrounded by acid gel and fluoride ions.


PROPERTIES

• Anticariogenic : large amounts of fluoride

• Soluble in saliva. High in acidic conditions

• Coefficient of thermal expansion: close to tooth structure : Microleakage is minimal

• Good optical properties

• pH remains low as 3 for few days : pulpal irritation

• pH remains below 7 even after a month: severe pulpal irritant

• Adhesion : mechanical bonding to tooth structure


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Translucency High pulpal irritant

Anticariogenic Highly soluble


POLYCARBOXYLATE CEMENT (ADA SP. NO. 96)

• Dennis Smith : 1968

• First cement system with adhesive bond to tooth structure

• Also known as polyacrylate cement

APPLICATION

• Luting alloy restorations

• Thermal insulating bases

• Cementing orthodontic bands

• Cementing SS crown in pediatric dentistry


COMPOSITION

80

POWDER %

ZnO

SnO / MgO 1 – 5

Aluminium oxide 10 – 40

Stannous Fluoride : Modified setting time

LIQUID

40% Aqueous solution of Polyacrylic Acid


SETTING REACTION

• Powder particles are attacked by the acid releasing Zn, Mg, Sn ions.

• Ions bind to the polymer chain via the carboxyl groups.

• Ions also react with carboxyl group of adjacent polyacid chains to form cross linked salts.

Bonding to tooth

• Polyacrylic acid reacts with Calcium ions via the carboxyl groups on the surface of enameland dentin.


MANIPULATION

• P:L = 1.5g : 1ml

• Mixing should be done on a surface that do not absorb liquid.

• Most of the powder should be incorporated into the liquid in one large increment.• Mixed over a small area with a stiff spatula• More powder is then added to obtain the required consistency• Mix should be used while it is still in the glossy state.

• Mixed rapidly in 30 – 40 secs

• Working time : 2.5 – 3.5 mins

• Setting time : 6-9mins (at 37°C)


Methods to Increase the working time

• Cooling glass slab :• Thickening of the liquid• Difficulty in mixing

• Powder refridgerated before mixing• Reaction occurs on cool surface, cool temperature retards the reaction without

thickening of the liquid.


PROPERTIES

• Solubility in water is low

• In organic acid with pH < 4.5 : increased solubility

• Reduced P:L ratio : increases solubility in oral cavity

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Film Thickness 25 µmCompressive Strength 55 - 85 MpaTensile Strength 8 - 12 MpaModulus of elasticity 6 GpaBond strength to enamel 3.4 – 4.7 MpaBond strength to dentin 2.1 MpaThermal diffusivity 0.223mm2/sec


BIOLOGIC EFFECTS

• Good biocompatibility• Low intrinsic toxicity• Rapid rise in pH towards neutrality

• Fluoride release


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Low irritation Lower compressive strength

Chemical bond to tooth structure and alloys

Greater viscoelasticity

Easy manipulation Need for clean surfaces for adhesion

Adequate strength Short working time

Low solubility

Adequate film thickness

Anticariogenic



ACRYLIC RESIN CEMENT

APPLICATION

• Cementation of restorations, facings and crowns

COMPOSITION

88

POWDER

MMA polymer or Copolymer

Benzyl Peroxide

Mineral Filler

Pigments

LIQUID

MMA monomer

Amine AcceleratorsDental Cements - Dr. Nithin Mathew

MANIPULATION

• Liquid is added to powder with minimal spatulation to avoid incorporation of air.

• Short working time – mix must be used immediately

• Excess material is removed only after final set.• When cement is hard, and not when rubbery since it creates marginal deficiencies.


PROPERTIES

• Stronger and less soluble

• Low rigidity and visco-elastic properties

• No effective bond to the tooth structure in the presence of moisture

BIOLOGIC EFFECTS

• Marked pulpal response


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High strength Marked pulpal irritation

High toughness Short working time

Low solubility Difficulty in removal of the excess cement


ADHESIVE RESIN CEMENT

• Formulated by adding the following to MMA monomer:• 4 methacryloxy ethyl trimellitate anhydride (4-META)• Tributyl boron initiator (helps in adhesion)

APPLICATION• Luting FPD and base metal• Bonding amalgam to dentin and composite


PROPERTIES

• (similar to acrylic resin)

• Stronger and less soluble

• Low rigidity and visco-elastic properties

• No effective bond to the tooth structure in the presence of moisture

• Moderate strength and high deformation under a load.

PROPERTIES

• Marked pulpal response


DIMETHACRYLATE CEMENTS

• Composition is similar to resin composites.

• Combinations of an aromatic dimethacrylate with other monomers containing variousamounts of ceramic filler.

APPLICATION• Bonding crowns, FPD, inlays and veneers.


COMPOSITION

95

POWDER

Borosilicate / silica glass

Polymer powder

Peroxide initiator

LIQUID

Bis-GMA / dimethacrylate monomer

Amine Accelerators


MANIPULATION

• Paste materials are mixed in the ratio 1:1 (equal lengths)

• P:L , thorough mixing to minimize air inclusion until uniform mix is obtained.

• On mixing, polymerization of monomers occurs leading to a highly cross-linked resincomposite structure

TYPES based on the method of curing• Chemically cured : for cementing ceramic, metal and opaque metal ceramic restorations• Dual cured : for cementing translucent restorations• Light cured / dual cured : used for both light cure and dual cure applications


PROPERTIES

BIOLOGIC EFFECTS

• Polymerization shrinkage

• Microleakage

97

Film Thickness 20 - 60 µmSetting Time 3 – 7 minsCompressive Strength 70 - 200 MpaTensile Strength 25 – 40 MpaModulus of elasticity 4 – 6 GpaSolubility 0.05 wt%


98


High strength Higher film thickness

Low solubility Microleakage

High micromechanical bonding Pulpal sensitivity

Difficulty in removing excess cement



PURPOSE OF A CAVITY LINER / VARNISH

• Serve as a physical barrier to ingress of bacteria/ bacterial byproducts.

• To provide therapeutic effect such as antibacterial, anticariogenic or pulpal anodyne effect.

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• Provide barrier for protection of pulp from residual reactantsdiffusing out of a restoration.

• Prevent oral fluids that may penetrate leaky restorations fromreaching the pulp through the dentin


CAVITY VARNISH

• A solution of one or more resins which when applied to the cavity walls, evaporates,leaving a thin resin film that serves as a barrier between the restoration and the dentinaltubules.

APPLICATION

• Prevents post-op sensitivity from galvanic shock

• Minimize penetration of acid from zinc phosphate cements

• Prevent diffusion of corrosion products from dental amalgam into dentin

CONTRAINDICATION

• Not to be used with Glass Ionomer Cement or Resin composites101Dental Cements - Dr. Nithin Mathew

COMPOSITION

MANIPULATION

• Applied by means of small cotton pellets / brush / applicator

• 2 – 3 layers – sufficient protection

• Volatile solvents evaporate quickly after application, leaving a thin resin film

102

Solid Copal Resin, Rosin Or Synthetic ResinSolvent 90% Ether, Acetone Or AlcoholMedicinal Agent Chlorbutanol, Thymol, Eugenol


PROPERTIES

103

Film thickness 1 – 4 µmTensile strength < 1 MpaLow solubility in water


CAVITY LINER

• Suspensions of calcium hydroxide in a volatile solvent.

• Used like a cavity varnish to provide barrier against the passage of irritantsfrom the cements and other restorative materials.

COMPOSITION

• Suspension of calcium hydroxide in an organic liquid such as methyl ethylketone or ethyl alcohol.


PROPERTIES

• No significant thermal insulation

• Soluble : should not be applied to margins of restorations

• Fluoride compounds are added to newer compounds to prevent secondary caries

105

Film thickness 1 – 4 µmTensile strength < 1 Mpa


MANIPULATION

• (Similar to varnishes)

• Applied by means of small cotton pellets / brush / applicator

• 2 – 3 layers – sufficient protection

• Volatile solvents evaporate quickly after application, leaving a thin resin film

Other Liners

• Type III Glass Ionomer Cement

• Type IV Zinc Oxide Eugenol


BASES

• Material that is used to protect the pulp in a prepared cavity by providing thermalinsulation

• Ie these are those cements commonly used in thicker dimensions beneath permanentrestorations to provide for mechanical, chemical and thermal protection to the pulp.

• Eg:• Zinc Phosphate• Zinc Oxide Eugenol• Calcium Hydroxide• Zinc Polycarboxylate• Glass Ionomer


INDICATIONS OF A CAVITY BASE

• To protect the pulp against thermal injury, galvanic shock and chemical irritation. (Zincphosphate under amalgam restoration)

• To withstand the forces of condensation of the restorative material and act as shockabsorbers. (Zinc phosphate under amalgam restoration)

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• To substitute dentin in deep cavities. (all high strength bases)

• To serve as intermediate bonding material between the toothand composite restoration. (GIC in sandwich technique)


CLASSIFICATION

• Low strength bases• Zinc oxide Eugenol, calcium hydroxides• Calcium hydroxide as a sub-base

• High strength bases• GIC, reinforced ZOE, Zinc phosphate, Zinc polycarboxylate• Used under direct and indirect metallic restorations• Only some bases are indicated under composite resins (GIC)


CLINICAL CONSIDERATIONS

Clinician must observe certain general guidelines for placement of bases:

• Base should be 0.5 – 0.75mm thick.• Very thick bases compromise the bulk of the restoration• Increase the potential for fracture of the restoration

• It is not recommended to remove sound tooth structure inorder to provide spacefor a base

• Bases are applied only on internal walls of the cavity preparation to preventdissolution by saliva


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Compressive strength(MPa )

Tensile strength(MPa )

elastic modulus(GPa)

Film thickness(mm)

Setting time(min)

Solubility(Wt%)

Bond strength to dentin

Pulp response

C TC(0C/cm)-1

CTE

ANSI /ADA 8

70 N/A N/A 25 5 0.20

ZnPO4 104 5.5 13.5 20 5.5 0.06 0 Moderate 3.11 X 10-4 35X 10-6/0C

Zn poly carboxylate

55 6.2 4.4 21 6 1.25 2.1 Mild

ZOE 25 1-2 0.22 25 4-10 0.04 0 Mild 3.98X 10-4

SilicoPhosphate

140 -170

7 - 25 3.5-4 1 Moderate 4.38 X 10-4

GIC 93-226 4.2-5.3 3.5-6.4 25 2.5-8 0.4-1.5 3-5 Mild -moderate

composite

25-70 - - <25 2-4 0-0.1 0 MildDental Cements - Dr. Nithin Mathew

CONCLUSION

• No single type of cement satisfies all of the ideal requirements or is best suited forall indications in dentistry

• Each situation must be evaluated based on the environmental, mechanical andbiological factors and finally decide on which material to be used in each case.


REFERENCES

• Phillip’s Science of Dental Materials : Anusavice ( 12th Edition )

• Phillip’s Science of Dental Materials : Anusavice ( 10th Edition )

• Craig’s Restorative Dental Materials ( 13th Edition )

• Craig’s Restorative Dental Materials ( 12th Edition )

• Dental Materials and their Selection : William J O’Brien ( 4th Edition )

• Materials Used in Dentistry : S.Mahalexmi ( 1st Edition )



Dental Cements

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