Seminar on Dental Cements

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Good morning

Seminar on:-

Presented by:-NAYASHA

MANCHANDAPG-2011 BATCH

Dental cements

Contents:- Definition

History

Uses of dental cements

General requirements for dental cements

Classification of dental cements

Components and properties

Setting reaction

Mixing process

The uses of dental cements

Definition Cement – substance that produces a solid

union between 2 surfaces (Oxford dictionary)

The word Cement is derived from the Roman word (i.e.) ‘opus caementitium’ which refers to the concrete used in masonry

Dental cement - ADA no: 96Substance that hardens to act as a base, liner, filling material or adhesive to bind devices & prostheses to tooth structure or to each other.(Anusavice)

Powder + Liquid

Pastelike or flowable material

Hardens to a rigid solid

History Cement has been introduced in dentistry for more

than 10 decades.

The first cement to be introduced into dentistry by Fletcher in 1873- Silicate cement.

In the same year, Zinc oxide eugenol cement was introduced by Chisolm.

In the year 1879 Zinc phosphate was introduced by Pierce

In the year 1930 Calcium hydroxide was introduced by Herman and has been widely applied for clinical use.

In the year 1968, an adhesive cement, Polycarboxylate was introduced – Smith

In the year 1971, a revolutionary discovery of Glass ionomer cement was made by Wilson and Kent.

Many manufacturers introduced different cements to serve different purposes.

More recently Resin based cements have been introduced.

Uses of dental cements

Luting agent• Temporary cementation• Permanent cementation

Pulp protection or cavity sealer Cavity varnish Liner Base

Uses of dental cement

Restotation Temporary Restoration Permanent Restoration

Others Root canal sealers Calcium hydroxide cement Bite registration material

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.

General requirements for luting agents Biocompatibility Retention High tensile strength, fracture

toughness, fatique strength Good marginal seal Low film thickness Ease of use Radiopacity Aesthetics

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

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

Classification of dental cements

BASED ON INGREDIENTS BASED ON TYPE OF

RESTORATION BASED ON USE ALONG WITH A

RESTORATION BASED ON TYPE OF BONDING BASED ON COMPOSITION

I. BASED ON INGREDIENTS: (Craig) Water-based

- Zinc phosphate- Zinc polycarboxylate- Glass ionomer cement

Resin-based- Composites and adhesive resin cements

Oil-based- Zinc oxide eugenol

II. Based on type of restoration: Permanent (few years) -Eg: GIC Intermediate (few weeks to months)-Eg: IRM Temporary (few days) -Eg: ZOE

III. Based on use along with a restoration: Liner Eg: Calcium Hydroxide, GIC Base Eg: ZnPO4

IV. Based on type of bonding: Mechanical - Micro (resin cements)

- Macro (Zn PO4) Chemical (GIC)

V. Based on composition:

ZnO powder

Ion leachable Glass particles

Phosphoric acid

Polyacrylic acid

Eugenol

Zinc Oxide Eugenol

Zinc Phosphate

Silicophosphate

Polycarboxylate

GlassIonom

SILICATE CEMENTS Introduced as anterior esthetic filling

material They are attacked by fluids and degrade

over time. pH is <3. High conc. pH- leaching – pulp

irritation Powder: Silica, alumina, sodium fluoride,

cryolite & calcium phosphate Liquid: phosphoric acid, aluminum, zinc

phosphate/Mg phosphate & water.

Si, Na,F, Ca,

H2O,H3PO4,Al, Zn

+Ca+2Al+3F-

Glass particleEtched periphery

Ca, Al, Na, ZnPhosphates andFluorides

REACTANTS PRODUCTS

Powder + liquid

Matrix is formed

Zinc Phosphate cement

One of the oldest luting cements.

Introduced by Pierce in 1879.

Also called ‘crown and bridge’ cement.

Zinc phosphate cement

Powder Liquid•Zinc oxide-90%

•Magnesium oxide-10%

•Other oxides (Bi2O3)

Silica

phosphoric acid

aluminum phosphate

zinc phosphate

Applications:

Luting of restorations High strength - base under metallic

restorations Luting of orthodontic bands and brackets Luting of posts and core

Classification: They are available as two typesType I- Fine grained for luting purpose(25μm)

Type II- Medium particle size used as thermal insulating bases (40μm)

Setting reactionPowder mixes with liquid

Phosphoric acid attacks the surface of particles

Releases zinc ions

Aluminum complexes with phosphoric acid and reacts with zinc

Zinc aluminophosphate gel is formed

ZnO+2H3PO4 Zn(H2PO4)2 + H2O

ZnO + Zn(H2PO4)2 Zn3(PO4)4. H2O (Hopeite)25

Exothermic reaction Adding of water can accerlate the

reaction. Loss of water can lengthen the setting

reaction.

Set cement:Unreacted zinc oxide embedded in a cohesiveamorphous matrix of zinc aluminophosphate.

Zn+Zinc aluminophosphate gel

UnreactedZnO

Zinc aluminophosphate matrix

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

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.

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.

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}

Mixing procedure

Finally: the small amount of powder is added again with brisk spatulation

To control the optimum consistency

Mixing time – 1.5-2 mins

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

Effects of manipulation on some properties.

Manipulative variables

PropertiesCompressive strength

Film thickness

Solubility

Initial acidity

Setting time

Decreased powder/liquid ratio

Increase rate of powder incorporation

Increase mixing temperature

Water contamination

Biocompatibility

Acid can penetrate into the dentinal tubule irritate pulp

pH of cement Liquid = 2.0 3 minutes after mixing = 4.2 24 hours = 5.5 48 hours = 7

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 Acidity is more

Clinical applications Zinc phosphate cement

Luting agent Base and temporary Restoration

Modified zinc phosphate Luting prostheses Luting the orthodontics band

Zinc oxide-eugenol cements Lower strength than Zinc phosphate cement. Sedative effect Mostly widely used temporary restorative

cement Developed from zinc oxy-chloride which was

slow setting Zinc oxide was then mixed with creosote and

oil of cloves Later it was replaced with eugenol

Most biocompatible material

Good insulator of the pulp-dentin organ

Antiseptic effect on remaining micro-organisms

Sedative and anti-inflammatory action on pulp dentin organ

Neutral pH-7

Zinc oxide-eugenol cement

Simple ZOE

Reinforced ZOE

EBA cement

Compositions of simple ZOE

Powder Zinc oxide Rosin : reduce the brittleness of the set cement Zinc stearate : plasticizer Zinc acetate : accelerator & improves strength

Liquid Eugenol olive oil : plasticizer Glacial acetic acid : accelerator

Setting reaction First (Hydrolysis of zinc oxide)

ZnO + H2O Zn(OH)2

Second (Acid base reaction to form a chelate)

Zn(OH)2+2HE ZnE2+H2O

Setting reaction

Water accelerates the reaction Zinc eugenolate is easily

hydrolized by moisture

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 slab

ClassificationAccording to specification no: 30 listed 4

types according to formulation 4 uses.

Type I – temporary cementation Type II – Permanent cementation Type III – Temporary restoration and thermal

insulating bases Type IV – Cavity liner

(According to anusavice 11th edition)

Type I – Temporary ZOE luting cement Type II – Long term ZOE luting cement Type III – Temporary ZOE restoration Type IV – Intermediate ZOE restoration

Specification requirements

Type Setting time [min]

Compressive strength[MPa]

Solubility[%]

Film thickness[µm]

Type I 4-10 35 maximum 2.5 25

Type II 4-10 35 maximum 1.5 25

Type III 4-10 35 maximum 1.5 -

Compressive strengthWeak cement- 3-55 MPa

Tensile strength0.32 -5.3MPa

Thermal propertiesExcellent thermal insulating property

SolubilityHigh solubility due to hydrolysis of zinc

eugenolate to form zinc hydroxide and eugenol

Biological propertiespH- 6.6 to 8 Least irritatingBacteriostatic and obtundant properties

EBA cement Orthoethoxy benzoic acid added to improve

properties of zinc oxide eugenol

EBA chelates with zinc forming an ionic complex (zinc benzoate)

Powder Add 20-30% of aluminium oxide

Liquid Add 50-60% ethoxybenzoic acid in eugenol

Compressive strength 55-75 MPa 53

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

POLYMER REINFORCED ZINC OXIDE EUGENOL

commercially called IRM or Kalzinol

Uses:Luting agentbasetemporary filling materialcavity linerroot end filling material

Powder:Zinc oxideNatural or synthetic resin (Polymethyl methacrylate)

LiquidEugenolAcetic acidThymol

Improved strength, shorter setting time, decreased brittleness, solubility

Clinical applications

Base Temporary cementation Permanent cementation Temporary restoration Permanent restoration

If cement contains eugenol, it is not to use with resin restorative material.

Advances To increase strength hexyvanillate and orthoethoxy

benzoic (HV-EBA) acid are used instead of eugenol.

LIQUID is mixed with ZnO powder.

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

Composition Powder Zinc oxide Magnesium oxide- sintering Bismuth and aluminum oxide- Increases strength. Stannous fluoride- Increases strength modifies setting time anticariogenic

Liquid Aqueous solution of polyacrylic acid Coplymers of carboxylic acid like itaconic acid

and tartaric acid 60

Manipulation Mix first half of powder to liquid to obtain the

maximum length of working time.

The reaction is thixotropic

1:1 for luting and 3:1 for restorative purposeMixing is done on a glass slab or non absorbent

paper pad.

The viscosity decreases when the shear rate increases

Setting reaction Acid- base reaction

Mixing of powder and liquid- ionisation of polyacrylic acid

Surface dissolution of powder- release of zinc. Magnesium and tin ions.

Zinc and calcium form ionic bond with carboxyl groups

On a clean calcific surface, it sets through chelation

Polycrylic acid forms complexes with proteins which promotes its property of adhesion.

Water plays an important role in the cement structure.

ZnO H2O PAA

ZnO + COOH

COOHHOOC -OOC

COO-Zn++

Zn++COO-

COO--OOC

ResidualZnO

Zinc polyacrylate gel

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.

Specification requirements Maximum film thickness: 25µm Minimum compressive strength: 50 MPa Working time: 3-5mins Setting time : 7-9mins Strength : compressive 55-67 MPa- less than Zn

Phosphatetensile- greater than Zn Phosphate

Dimensional stability: 1-6% Bond strength : to enamel- 3.45-13.5 MPa

to dentin- 2.07 MPa Solubility: 0.10-0.25% Biological properties: pH-1.5 and rapidly neutralised

by powder.Larger size of polyacrylic molecule and its binding to

calcium and proteins limits it diffusion through the dentinal tubules

Applications

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

Glass ionomer cement Or called Polyalkynoate cements

Conventional glass ionomer cement

Resin-modified glass ionomer cement [RMGICs]

Developed by Wilson and Kent as derivatives of silicate cements.

Introduced first as ASPA (alumino silicate poly acrylate)

Has been referred to as ‘man made dentin’ or ‘dentin substitute’

DEVELOPMENTDEVELOPMENTTimeline for “direct restorative materials” usageTimeline for “direct restorative materials” usage

19701970 19801980 2000200019901990

Dental AmalgamDental Amalgam

Dental CompositeDental Composite

Glass IonomerGlass Ionomer

First GIC in 1972First GIC in 1972Dentsply A.S.P.A.Dentsply A.S.P.A.

A.S. = A.S. = AAluminoluminossilicate glassilicate glassP.A. = P.A. = PPolyacrylic olyacrylic aacid in watercid in water

CLASSIFICATIONCLASS I – ConventionalCLASS II –Metal ModifiedCLASS III – light curedCLASS IV –hybrid resin modified

Conventional GIC’sTYPE I- LUTING, liningTYPE II- restorationsTYPE III- liners and basis

TYPE IV – fissure sealants

TYPE V – orthodontic cements

TYPE VI- core build ups

Composition Powder• Silica-41.9%• Alumina-38.6%• Fluorides of calcium sodium and aluminum-25%• Calcium aluminum fluorosilicate glass

Liquid Polyacid

Copolymer of polyacrylic / itaconic acid/ maleic acid & Tricarboxylic Acid-40-55%

Tartaric acid : Improves Handling Characteristics-5-15%

Water-30%

Setting reaction

There are three stages: Dissolution Gelation Hardening.

Water hardening or water setting

Silica gel

Glass core

Polyacid liquid

Hydrogen ions

Polyacid liquid

Cross-linkedpolyacid

Gelation

Calcium ions have more reactivity than aluminium ions.

This is critical phase of contamination.

Polyacid liquid

Al3+ -COOH

Cross-linkedpolyacid

Hardening

Last as long as 7 days.

The reaction of aluminium ions provides the final strength of set cement.

Cross-linked polyacid

Silica gel80

SiO2,Al2O3,Na, Ca, F

Residual Glass Particle

POLYACRYLATE HYDROGEL(initially Ca polyacrylate geland later Al polyacrylate gel)

Si+4, Al+3, Ca+2, Na+, F- Ions

SiO2,Al2O3,Na, Ca, F

Ca+2 F-

GLASS IONOMERSGLASS IONOMERSHYBRID = HYBRID = SC [Powder]SC [Powder] and and PCC [Liquid]PCC [Liquid] = A.S.P.A. = A.S.P.A.

FLUORO-ALUMINO-SILICATEFLUORO-ALUMINO-SILICATEPARTICLEPARTICLE

CEMENTCEMENTMATRIXMATRIX

F-1, Ca+2, Al+3, Si+4

Initialdissolution

for startingreaction

rapid earlyF release

from matrixSlow long term

F releaseby diffusionfrom particle

FLUORIDE RELEASEFLUORIDE RELEASEFluoride comes from matrix and particles at different rates.Fluoride comes from matrix and particles at different rates.

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.

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.

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.

1. Cement2. Liner / Base3. Restoration4. Core / Foundation5. (Sandwich Restoration)7. Retrograde Filling Material8. P/F Sealant9. Root Caries Cervical Restoration10. Temporary, or ART Restoration

Technical modifications:> P/L Precapsulated> Addition of etching and then BA> Addition of different reinforcing fillers> Finer and finer particle sizes

General Properties:> Strength> Adhesion> Biocompatibility> Fluoride release

APPLICATIONSAPPLICATIONSGIC has been tried for about every conceivable application.

Manipulation of GIC:Use a plastic or agate spatula with a paper

pad. Powder is divided.First increment is mixed with the liquidSubsequent increments are folded in to

preserve the cross-linked structure.

Modified GI

Cermet Combination of glass and metal. No significant improvement in the

strength. More wear resistance and short

setting time.

Resin-modified GI88

MODIFICATIONS OF GIC Metal-modified GIC

- Cermet: Fusing silver to glass powder by sintering- Miracle mix: incorporating silver alloy powder with type II GIC powder. (silver alloy admix)

Less fluoride release from cermet

More fluoride release from admix cement

Resin-modified glass ionomer cement Add polymerizable function groups

Both chemical & light curing

Overcome moisture sensitivity & low early strength

- Names: Ligth cured GICs, Dual cured GICs - , Tri cured GICs, Hybrid ionomer, Compom

-ers, Resin ionomers

Setting reaction Polymerization

initial setting - Acid base reaction

maturing process & final strength Heat released from the

polymerization reaction.

Properties

Higher strength than conventional GI

Higher adhesion to resin material

Less water sensitivity Can be polished after curing

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

Applications

Type I : Luting agent Type II : Restorative material Type III : Base and liner

RelyX™ Luting Plus Cement Clicker™ Dispenser

Conventional GI for cementation

GI restorative material

Adhesive resin cement Occured later from the direct filling

Become popular because of the improved properties, high bond strength.

Resin cement is flowable composite resin.

Trade name:-RelyX ARC Adhesive Resin Cement Paste A3 in Clicker Dispensing System

From 3M

RelyX™ Unicem Self-Adhesive Universal Resin Cement Aplicap™ Capsule Translucent Shade Refill

Calcium hydroxide cement Used as base and liner

High pH value

Good biocompatibility

Composition

2 Pastes system Base

Salicylate reaction Calcium tungstate and barium sulfate radiopacity

Catalyst Calcium hydroxide

Properties Lower compressive strength than others

Resist to the condensation force of amalgam filling

High pH 9.2-11.7 [Alkaline]

Bactericidal

High solubility102

Properties Stimulate the repairative dentin

formation in the area of thin dentine [<0.5mm]

Stimulate the dentine formation in the exposed-pulp lesion [Direct pulp capping]

Comparable properties of cements

Compressive strength [MPa]

Zinc phosphate Polycarboxylate GIC RMGIC Resin cement

Zhen Chun Li and Shane N. White, 1999 105

Bond strength

Zinc phosphate GIC RMGIC Resin

Separation forces [MPa]

Sule Ergin and Deniz Gemalmaz, 2002106

Film thickness [µm]

Zinc phosphate Polycarboxylate GIC RMGIC Resin

Shane N. White, Zhaokun Yu, 1992 107

Others

Solubility ZOE > Polycarboxylate > Zinc

phosphate~GIC > Resin cement

Irritation to pulp tissues Resin~Zinc phosphate > GIC >

Polycarboxylate > ZOE~Calcium hydroxide

References Textbooks

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

Textbook Robert G. Craig

Restorative dental materials9th editionMosby company 1993

References Textbook

Richard van NoortIntroduction to dental materials2nd editionMosby company 2002

Journals Li ZC, White SN. Mechanical properties of dental luting

cements. J Prosthet Dent 1999;81(5):597-609 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

Thank you

Seminar on Dental Cements

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