Dental cements

Dental CementsDr. Deepak K Gupta

Dental Cements

• They are materials that set intraorally and that are commonly used to join a tooth and a prosthesis or restoration of carious tooth.

• The use of dental cements:– Luting/cementation of prosthesis and orthodontic

appliance– Restoration– Pulp Therapy– Obtundant– Liners & Bases– Root canal sealers

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Classification based on Application

• Type I : Luting agents

– Type I : Fine grain for cementation and luting

– Type II : Medium grain for bases, orthodontic purposes

• Type II : Restorative application

• Type III : Liners or base applications


Classification based on bonding Mechanism


General Properties : Strength

• Tensile Stress: a stress caused by a load that tends to stretch or elongate a body.

• Compressive Stress : associated with acompressive strain.


General Properties : Strength• Shear stress : resist the

sliding or twisting of one portion of a body over another.

• Flexural Stress : Caused due to bending of a body in the opposite direction of bend.

• All this stresses act in combination on cements depending on nature and direction of force.

• The ability to withstand this stresses comprises of strength of cement


General Properties : Modulus of elasticity (MOE)

• Measure of stiffness of cement.

• Ability to return back to its original shape after the deformative force


General Properties: Solubility and disintegration

• Long term survivability of restorations.

• Solubility and disintegration of cement lead at the margin leads to inflammation, secondary caries or sensitivity


General properties : Film thickness

• A thinner film is more advantageous for luting.

• It depends on various factors– Particles Size

– P/L ratio

– amount of force applied during seating of the prosthesis.

– Direction in which force is applied

– Design and fit of prosthesis

• ADA sp. No. 96 recommends acceptable thickness of 50 µm


Biological properties

• pH : ideally it should be neutral, but most of cements are acidic but it loses its acidity gradually with time

• Pulpal response : mild to moderate response is acceptable depending on its use

• Pulp protection : it should not irritate the pulp. So its advised not to use to thin mixes


Acid – Base Cement


Acid – Base Cement

• It can be either– Non-Eugenol

• Zinc Phosphate

• Zinc polycarboxylate

• Glass ionomer

• Resin-modifid glass ionomer

• Compomer

– Eugenol Based• Zinc oxide–eugenol

• Zinc oxide–eugenol (EBAmodifid)


Zinc Phosphate Cement

• First cement appearing in literature.

• USE

– Permanent cement for indirect restorations including inlays, onlays, crowns, and bridges

– Orthodontic cement

– High-strength base


Zinc Phosphate Cement : Composition

Powder

Zinc Oxide > 75 % Main Constituents

Magnesium Oxide 13 % Aids in sintering

Barium oxides 0.2 % Radioopacity

Other oxides (Bismuth trioxide, Calcium oxide)

1.4 % Smoothness of mix and fillers

Liquid

Phosphoric Acid 38 % – 59 % Reacts with ZnO

Water 30% to 55% Controls the rate of reaction

Alumuminium Phosphate 2% to 3% Buffer

Zinc phosphate (up to 10%)


Setting Reaction

• When mixed, phosphoric acid dissolves the zinc oxide, which reacts with the aluminum phosphate and forms zinc aluminophosphategel on the remaining undissolved zincoxide particles.

• Mixing Time : 1.5 – 2 min

• Setting Time : 2.5 – 8 min

• Exothermic Reaction


Control of setting time

• Manufacturing process• Sintering temperature : directly proportional

• Particle size : inversely

• Water content : inversely

• Buffering agent : directly

• Operator control• Temperature : inversely

• p/l ratio : directly

• Rate of addition of powder to liquid : directly

• Mixing time : directly


Properties

• C.S. = 104 – 119 MPa

– 70 % strength in 30 min, max in 24 hrs

– More the powder, greater strength.

– Water content: both loss or gain reduces the strength.

• T.S. = 5.5 MPa, brittle

• MOE = 13.7 GPa, stiff and resistant to elastic deformation


Properties

• Solubility = 0.06 % - low– Thick mix : less solubility– Water content : any change increases the solublity– Moisture : increases

• Film Thickness = • Thermal insulator - good• Adhesion properties – micromechanical• pH = 2 (at time of cementation) , 5.5 (24 hrs)• Pulpal response – moderate• Pulp protection – RDT 1.5 mm

• Avoid thin mixes• Liners & bases : ZOE, CaOH, cavity varnish


Clinical Manipulation• Obtain a clean, cool, dry glass slab and flexible cement spatula.• Fluff the powder and dispense appropriate amount for

cementation.• Divide the powder in 1/2, then into 1/4, then divide one of the

fourths into 1/8, and then one of the eighths into 1/16.• Dispense the liquid (6 to 12 drops) holding the dropper vertical to

the glass slab.


Clinical Manipulation• Incorporate 1/16 portion of powder into

the liquid and mix for 15 seconds. Repeat by adding the 2nd 1/16 andmix for 15 seconds.

• Add the eighth portion and mix the material using three quarters of the glass slab for 15 second

• Add one of the quarters and spatulate for 20 seconds; follow by a second quarter, which is also spatulated for 20 seconds.

• Add enough of the last quarter of powder to achieve the consistency the dentist requires. Mix should be completed in2 minutes.

• Ropy consistency for restoration and putty like consistency for base application.


Advantage and disadvantage

• Advantage

– Proven reliablity

– Good C.S.

• Disadvantage• No chemical adhesion

• No anticariogenic properties

• Pulp irritation

• Poor esthetics


Zinc Polycarboxylate

• First dental cement to exhibit chemical bonding to teeth.

• Not used for restorative purposes because the cement is opaque

• USE– Permanent cement for

crowns, bridges, inlays, and onlays

– Orthodontic cementation

– High-strength base


Zinc Polycarboxylate Cement : Composition

Powder

Zinc Oxide 89 % Main Constituents

Magnesium Oxide 9 % Aids in sintering

Barium oxides 0.2 % Radioopacity

Other oxides (Bismuth trioxide, Calcium oxide)

1.4 % Smoothness of mix and fillers

Liquid

Polyacrylic acid or a copolymer of acrylic acid

32 % – 48 % Reacts with ZnO

Other carboxylic acids, such as itaconic acid or maleic acid

30% to 55% Controls the rate of reaction

Stannous floride - adjust the setting time & increase the strength


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 particlesare dispersed.

• Mixing Time : 30 seconds – 2 min• Setting Time : 6 to 9 min


Properties

• C.S. = 55 MPa

• T.S. = 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.


Properties

• Solubility = 0.6 % - more soluble than zinc phosphate– Marginal dissolution is more which increases in acids

like lactic acid.– Low p/l increases the solubility

• Thermal insulator - good• Adhesion properties – micromechanical &

chemical (carboxyl group of tooth structure)• Opaque• Anticariogenic properties – less as compared to

GIC.


Clinical Manipulation• Obtain a clean, cool, dry glass slab and flexible cement spatula.• Fluff the powder and dispense appropriate amount for

cementation.• Divide the powder in 1/2, then into 1/4, then divide one of the

fourths into 1/8, and then one of the eighths into 1/16.• Dispense the liquid (6 to 12 drops) holding the dropper vertical to

the glass slab.


Clinical Manipulation• Incorporate 1/16 portion of powder into

the liquid and mix for 15 seconds. Repeat by adding the 2nd 1/16 andmix for 15 seconds.

• Add the eighth portion and mix the material using three quarters of the glass slab for 15 second

• Add one of the quarters and spatulate for 20 seconds; follow by a second quarter, which is also spatulated for 20 seconds.

• Add enough of the last quarter of powder to achieve the consistency the dentist requires. Mix should be completed in2 minutes.

• Ropy consistency for restoration and putty like consistency for base application.


Advantage and disadvantage

• Advantage– Chemical bonding

– Good marginal adaptation

– Anticariogenic properties

– Mildly acidic

• Disadvantage• Less C.S.

• Poor esthetic

• Solublity high


Glass Ionomer Cement


Introduction• developed in the 1970s• tooth colored, anticariogenic

restorative materials• combined properties of silicate

cements and poly carboxylatecements

• minimal cavity preparation as it bonds adhesively to tooth structure

• Why glass ionomer cement ?– the powder is glass – the setting reaction and adhesive

bonding to toothstructure is due to ionic bond


Introduction

• Synonyms

– Poly (alkenoate) cement

– ASPA (alumino silicate polyacrylic acid)

• Commercial preparation

– Aquacem,

– Fugi I — Type I

– Chem Fil — Type II

– Ketac bond — Type III

– Vitra bond — Light cure GIC



Classification of Glass IonomerCement (GIC)

• Type I: Luting crowns, bridges, and orthodontic brackets

• Type IIa: Esthetic restorative cements

• Type IIb: Reinforced restorative cements

• Type III: Lining cements, base


Glass Ionomer Cement : CompositionPowder

Silica (SiO)2 41.9

Alumina (Al2O3) 28.6

Aluminium flouride (AlF3) 1.6

Calcium flouride (CaF2) 15.7

Sodium flouride (NaF) 9.3

Aluminium phosphate (AlPO4) 3.8

Barium/strontium oxide radiopacity

Liquid

Polyacrylic acid or a copolymer of acrylic acid

40-50 % Reacts with SiO and Al203

Other carboxylic acids, such as itaconic acid or maleicacid

30% to 55% Controls the rate of reaction

Tartaric acid rate-controlling additivefacebook.com/notesdental

Chemistry: Setting Reaction• Powder and liquid are mixed together• Acid attacks the glass particles leaching calcium,

aluminium, sodium and flouride ions into the aqueous medium.

• Polyacrylic acid chains - cross-linked by the Al ions which is further replaced by calcium ions –24 hrs

• Sodium and fluorine ions from the glass do not participate in the cross-linking

• The cross-linked phase becomes hydrated over time as it matures

• Undissolved portion of glass particles is sheathed by a silica-rich gel


Chemistry: Mechanism of Adhesion

• Chelation of the carboxyl groups of the polyacrylicacids with the calcium -apatite of the enamel and dentin

• Similar to polycarboxylatecement


CLINICAL MANIPULATION

• Surface Preparation– Pumice slurry: remove the smear layer produced

by cavity preparation

– Tooth may be etched for 10 sec

• phosphoric acid (34% to 37%)

• organic acid like polyacrylic acid (10% to 20%)

– Followed by a 20- to 30-second water rinse

– Dried but not desiccated

– Must remain uncontaminated by saliva or blood



• Material Preparation– supplied in two bottles

(powder and liquid) or capsules containing preproportioned powder and liquid

– P/L ratio recommended by the manufacturer should be followed

– powder should be incorporated rapidly into the liquid using a stiff spatula (AGATE) on a cool paper pad



• Normally half of the powder is mixed intothe liquid for 5 to 15 seconds

• rest of the powder is then quickly added

• Mixed until a uniform, glossy appearance: indicates the presence of unreacted polyacid, which is critical for bonding to the tooth.



• Placement of Material– slightly overfilled with GIC restorative

– Surface should be covered with a plastic matrix for about 5 minutes - protect the material from gaining or losing water during the initial set

– surface must immediately be protected with the varnish supplied with the GIC or with petroleum gelly

– excess GIC is removed from the margins

– Finishing is improved as the cement sets


PROPERTIES

• Setting Time

– Type I — 4-5 minutes

– Type II — 7 minutes

• Release of Fluoride• release fluoride in amounts comparable to those released

initially from silicate cement

• inhibit enamel and dentin demineralization

• But its clinical efficacy is yet to be proved, where it shows anticariogenicity in vitro


PROPERTIES

• Greater pulpal reaction than ZOE cement but less than zinc phosphate cement

• luting agents pose a greater pulpal hazard than restorative agents

• Protective liner such as Ca(OH)2 should be used if the preparation is closer than 0.5 mm to the pulp chamber

• Compressive strength is similar to that of zinc phosphate


PROPERTIES

• Modulus of elasticity is only about half that of zinc phosphate cement

– less stiff and more susceptible to elastic deformation

– less desirable than zinc phosphate cement to support an all-ceramic crown

• greater tensile stress could develop in the crown that is supported by the GIC under occlusal loading

• More vulnerable to wear than are composites


Modification of GIC

• Metal-reinforced GIC

• High-viscosity GIC

• Resin-modified GIC (hybrid ionomer)

• Calcium aluminate GIC

• Compomer


METAL-REINFORCED GLASS IONOMER CEMENTS

• Metallic fillers - improve their fracture toughness and stress-bearing capacity

• Silver alloy powder or particles of silver sintered to glass

• Grayish and more radiopaque

• Also known as alloy admixture and cermet.

• Fluoride release rate decreases over time.


METAL-REINFORCED GIC : Types

• Silver alloy admixed: Spherical amalgam alloy powder is mixed with type II GIC powder

– Ex: Miracle Mix

• Cermet: Silver particles are bonded to glass particles.

– Done by sintering of a mixture of the two powders at a high temperature

– Ex: Ketac Silver


METAL-REINFORCED GLASS IONOMER CEMENTS

• Adhesion and fluoride release

– useful for core buildups of teeth – occlusalsurfaces of primary molars

• Compared with conventional glass ionomersor amalgam or compites

– It exhibit no improvement in clinical performance and life expectancy


HIGH-VISCOSITY GLASS IONOMER CEMENT

• Atraumatic restorative treatment (ART)– preventive and restorative caries management

– Where electricity or piped water systems is absent

– hand instruments for opening tooth cavities.

• GIC remains the choice of filling material in ART• Releases fluoride and bonds chemically to tooth structure

• Conventional GIC was low in viscosity to flow in non-prepared carious portion of teeth• So high viscosity GIC was developed in an attempt to overcome

these difficulty


HIGH-VISCOSITY GLASS IONOMER CEMENT

• Contain smaller glass particle sizes and use a higher P/L ratio,

• Greater compressive strength• Excellent packability for better handling

characteristics.• Indication

– Core buildups, – Primary tooth fillings, – Non-stress-bearing restorations,– Intermediate restorations


RESIN-MODIFIED GLASS IONOMER CEMENT (HYBRID IONOMER)

• Water-soluble methacrylate-based monomers -replace part of liquid component of conventional GIC.

• Also known as hybrid ionomer cement• Monomers can be polymerized - chemical or light

activation or both.• Also contain nonreactive filler particles -

lengthens the working time– improves early strength– makes the cement less sensitive to moisture during

setting


RESIN-MODIFIED GLASS IONOMER CEMENT (HYBRID IONOMER)

• Liquid– water solution of polyacrylic acid,

HEMA– polyacrylic acid modified with

methacrylate

• Powder: same as that for conventional GICs in addition to initiators, such as camphorquinone.

• Sandwich technique:– resin-modified glass ionomer to

seal the dentin– It provides the benefit of fluoride

release – Over which a layer of resin

composite is filled on the rest of cavity





Mechanism of Bonding

• Same as that for conventional GICs• Hybrid layer: cement that infiltrates the tubules,

but no studies has got any conclusive evidence.• Higher bond strengths – enhanced

micromechanical interlocking to the roughened tooth surface

• Comparatively more microleakage– More shrinkage of hybrid ionomers– Low wettablity: lower water and carboxylic acid

contents

• Water resorption – by HEMA


Clinical Manipulation

• Indication– Liners, base materials, – Fissure sealants, – Core buildups, – Restoratives, – Adhesives for orthodontic brackets, – Repair materials for damaged amalgam cores or

cusps,– Retrograde root filling materials

• Surface conditioning of the tooth structure with a mild acid - bond formation


CALCIUM ALUMINATE GIC

• Hybrid product with a composition between that of calcium aluminate and GIC

• Luting fixed prostheses• calcium aluminate component is made by

sintering a mixture of high-purity Al2O3 and CaO.• Powder: calcium aluminate, polyacrylic acid,

tartaric acid, strontium-fluoro-alumino-glass, and strontium fluoride

• Liquid: liquid component contains 99.6% water and 0.4% additives


COMPOMER

• Polyacid-modified composite made by incorporating glass particles of GIC.

• Water-free polyacid liquid monomer with appropriate initiator.

• Properties distinctly different from those of composites and GIC

• Rationale

– integration of the fluoride-releasing capability of GIC

– Durability of composites


CHEMISTRY AND SETTING

• Usually one-paste, light-cure materials - restorative applications

• Powder-liquid systems: luting applications • These water free materials contain

– nonreactive inorganic filler particles,– reactive silicate glass particles, – sodium fluoride,– polyacidmodified monomers: diester of 2-hydroxyl methacrylate

with butane carboxylic acid and photoactivators.

• Setting of one-component compomers is initiated byphotopolymerization of the acidic monomer.

• Sensitive to moisture


CHEMISTRY AND SETTING

• Functionally hydrophobic • To a lesser extent, and intraorally they absorb

water from the saliva• These begins the slow acid base reaction of GIC• Powder: strontia-alumina-fluorosilicate glass,

metallic oxides, and initiators (chemical/ light/ dual cure)

• Liquid: polymerizable methacrylate/carboxylic monomers, multifunctional acrylate monomers and water.



• Bonding Mechanism

– One-paste - require a dentin-bonding agent - do not contain water (self-adhesive)

– Bond strength of one-paste compomers similar to or higher than that of hybrid ionomers.

– Powder-liquid compomer: cements for luting are self-adhesive, because water in the liquid makes the mixture acidic, like hybrid ionomers.



• Restorative compomer– Low stress-bearing areas such as Class III and V prepared cavity,– Alternative to glass ionomer restoratives– Resin based composites. – Etching should be done– Finished just like resin composites.

• Luting systems– Prostheses with a metallic substrate. – The cement mixture is placed only on the prosthesis - seated with

finger pressure. – The margin should be light-cured immediately to stabilize the

prosthesis. – The chemical-cure compomers complete their setting reaction in

approximately 3 minutes in the oral environment


RESIN CEMENTS

• Low-viscosity versions of restorative composites.

• Virtually insoluble in oral fluids.

• ISO classifies resin cements according to curing mode as – class 1 (self-cured)

– class 2 (light-cured)

– class 3 (dual-cured)


RESIN CEMENTS• APPLICATIONS

– Cementation of crowns and bridges (etched cast restorations)

– Cementation of porcelain veneers and inlays.

– For bonding of orthodontic brackets to acid-etched enamel

• Commercial Names– Panavia Ex– Infinity– Porcelite dual cure (Kerr)


COMPOSITION

• Powder– Resin matrix (diacrylate monomer, Bis-GMA, UDMA,

TEGDMA)– Inorganic fillers– Coupling agent (organo silane)– Chemical or photo initiators and activators

(Camphorquinone, a tertiary amine, Benzoyl peroxide)– tri-n-butylborane (TBB) as catalyst

• Liquid– Methyl methacrylate– Tertiary amine.– 4-META, MDP



• monomeric component irritating to the pulp - pulp protection with a liner.

• Chemically cured resin cements– all types of restorations– supplied as powder and liquid or two pastes,– mixed on a paper pad for 20 to 30 seconds.– slow and provides extended working time,

• Dual-cure cements– mixing similar to that for the chemical-cure systems.– Curing proceeds slowly until the cement is exposed to the

curing light– Should not be used in prostheses thicker than 2.5 mm


CLINICAL MANIPULATION: treatment of the prosthesis

• Metallic Prostheses– roughened by electrochemical etching or by grit blasting with 30- to

50-µm alumina particles at an air pressure

• Polymeric Prostheses– polymer’s surface should be grit-blasted to increase the roughness for

mechanical adhesion

• Ceramic Prostheses– Some dental ceramic restorations are translucent – shade of luting

agent must be matched.– Silica based (feldspathic porcelain): etched with hydrofluoric acid and

a silane coating is applied prior to cementation,– Alumina and zirconia-based ceramics: grit blasting

• Orthodontic Brackets– mechanical retention, such as the metal mesh of a metal bracket or

retentive dimples or ridges on ceramic or polymer brackets


ZINC OXIDE−EUGENOL CEMENT• Used for luting and intermediate restorations because of

its medicament quality and neutralpH.

• Cements of low strength• To improve the strength many modification have been

introduced– EBA—alumina modified– Polymer—reinforced zinc oxide-eugenol cements.


ZINC OXIDE−EUGENOL CEMENT

• ANSI/ADA Specification No. 30– Type I: temporary cementation;

– Type II: long-term cementation of fixed prostheses;

– Type III: temporary fillings and thermal insulating bases;

– Type IV: intermediate fillings

• Also used as a root canal sealer and periodontal dressings.


ZINC OXIDE−EUGENOL CEMENT

• 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



Composition

• Formulated as a powder-liquid or two-pastesystem.

• Powder or Base Paste: zinc oxide particles.

• Liquid or Accelerator Paste: eugenol.

• Water in the eugenol solution that hydrolyzes the zinc oxide to form zinc hydroxide.

• Zinc hydroxide and eugenol chelate and solidify to form zinc oxide eugenolate.

• Slow but proceeds more rapidly in a warm, humidenvironment.


Composition

• Best suited for provisional applications.• Residual free eugenol interferes with the proper

setting of resin-based composites or resin cements.

• Various types of carboxylic acids have been used to replace eugenol and produce a ZOE-like material.

• Zinc oxide-noneugenol cements– EBA-Alumina modified cements– ZOE plus polymer


Modification

• EBA-ALUMINA MODIFIED CEMENTS– Liquid: substituted by orthoethoxybenzoic acid (EBA)

for part of the eugenol liquid– Powder: alumina

• ZOE plus polymer– Liquid: eugenol– Powder: 20% to 40%: fine polymer particles

• Zinc oxide particles - surface treated with carboxylic acid

• Compressive strength (CS): acceptable but their strength values are inferior to those of zinc phosphate, glass ionomer, and resin cements



• Temporary ZOE cements– luting provisional acrylic crowns and fixed partial dentures.– last a few weeks at most– seal the dentinal tubules surprisingly well against the ingress of oral

fluids and have a sedative effect on the pulp– can cause pulp necrosis and should not be used directly on a pulp

• Intermediate Restoration– When mixed to a stiff putty like consistency– Restorative material for at least a year.– cool glass slab slows the setting to enable the formation of a thick

consistency,– not be colder than the dew point- water will condense onto the

cement and accelerate the reaction

• ZOE luting cements: high film thicknesses


MINERAL TRIOXIDE AGGREGATE CEMENTS

• A new category of cement –based on Portland cement

• Good sealing ability and biocompatibility.

• Contains oxides in hydraulically active ceramic compound– Calcium oxide (calcia, CaO), – Aluminum oxide (alumina,

Al2O3)– Silicon dioxide (silica, SiO2)


MINERAL TRIOXIDE AGGREGATE CEMENTS

• Indication

– Pulp capping

– Apexification

– Apexogenesis

– Root canal sealers


References

• Phillips' Science of Dental Materials- Phillip Anusavice_12th

• Basic Dental Materials -2nd.ed Mannapalli

• Clinical Aspects of Dental Materials Theory, Practice, and Cases, 4th Edition

• Craig's Restorative Dental Material 13th edition


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Health & Medicine

Dental cements