select of cement

Selection ofCement

Selection ofCement

Group one | | Level 8 Group one | | Level 8

Reference: Rosenstiel. Land. Fujimoto.4 th ed. pages: 909-927.

Selection of Cement

Reference: Rosenstiel. Land. Fujimoto.4th ed. pages: 909-927.

Presenting By :

Osama Almasry

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Cementation is defined as, “The process of attaching parts by means of a cement” –GPT.

•Cementation

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The clinical success of fixed prosthodontic restorations can be complex and involve multifaceted procedures. Preparation design, oral hygiene/microflora, mechanical forces, and restorative materials are only a few of the factors which contribute to overall success. One key factor to success is choosing the proper luting cement. This clinical update will review several luting cements, their physical properties, clinical implications, and recommendations for usage.

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An ideal luting cement would have: easy manipulation, low film thickness, long working time with rapid set, low solubility, high compressive and tensile strengths, high proportional limit, adhesion to tooth/restoration, anticariogenicity, biocompatibility, and translucency or radiopacity. Physical properties should be taken into consideration along with handling characteristics, technique sensitivity, and results from long term clinical trials .

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Most cements are formed by an acid-base

reaction. Liquids may be phosphoric acid, polyacrylic

acid, or eugenol. Powders are either zinc oxide or aluminosilicate glass. Resin cements, however, are not acid-base formed but utilize BIS-GMA or urethane dimethacrylate resins. Cements can be classified into five groups: phosphate bonded, polycarboxylate bonded, phenolate bonded, resin cements, and glass ionomer/hybrid cements.

Long working time.Adhere well to both tooth structure and

cast alloy.Provide a good seal.

Non-irritating, non-toxic to both pulp and surrounding supporting structure.

Have adequate strength properties.Being compressible to thin layers i.e. have

low viscosity; low solubil i ty.Exhibit good working and setting

characteristic.Easily to be removed after sett ing.

Fluoride release.

Zinc phosphateZinc si l icophosphate Zinc polycarboxylate

Zinc oxide-eugenol with/without EBAGlass ionomerAdhesive resins

Resin modif ied GIs

Non-adhesive mechanical luting

Micro-mechanical bonding

Molecular adhesive

. Fleck’s (Mizzy) is an example of zinc phosphate cement

Composition: ZnO powder and phosphoric acid

Advantages:Long cl inical track record (used cl inical ly for

over 50 years(.Specimens of cement retrieved from old

castings (>40 yrs) show high chemical stabil i ty .Adequate strength (80-110 MPa c.s,5-7 MPa

t.s(.Reasonable working t ime (3-6min w.t, 5-14 s.t(.Excess material can be easily removed.

Disadvantages:Water-sensit ive during sett ing; microleakage; high

solubil i ty especial ly in acid environment (0.05 to 3.3% in d.w, 20 to 30 t imes higher in acids(.

Pulp irri tation Low init ial pH (1-2 after mixing, below 4 to 1 h,6-7 after 24 h); (use of varnishes?(.

Lack of antimicrobial actionBritt leness,

lack of adhesion.

It is good for general/routine use and recommended for long

span f ixed partial dentures due to its r igidity.

Good ForGood For ? ?

High compressive strength (152 MPa) and a moderate tensile

strength (9.3MPa( .Excessive f i lm thickness 88 µm at

the occlusal surface under an actual casting.

An acidic pH that may be harmful to the pulp.

. Durelon (3M ESPE AG) and Tylok Plus (Dentsply/Caulk) are examples of polycarboxylate cements.

Composit ion: The powder is zinc oxide with 1% to

5% tin or magnesium oxide, 10% to 40% aluminum oxide or other

reinforcing fi l ler, the acid is 40% (high MW) polyacrylic acid or

acrylic acid coplymer with other organic acids.

Good for cementing crowns and 3-unit bridges.

Exhibits specif ic ( low) adhesion to tooth structure because it chelates with the calcium.

Adhesion to some alloys. Higher tensile strength (8-12 MPa) compared to

zinc phosphate cement, but signif icantly lower compressive strength (55-85 MPa(.

Anticariogenic in nature but this property is less than that of GIC.

Biocompatible to the pulp , rapid r ise of the cement PH toward neutral ity.

Lack of post operative sensit ivity. (excellent for sensit ive teeth (

Film thickness comparable to those of zinc phosphate cements

Solubil i ty in dist i l led water 0.1% to 0.6%.

Disadvantages◦It is thixotropic in nature. Hence, i t may be too

thick and wil l not f low adequately.◦Short (2.5min)working time as compared to that

of Zn/Po cement(5min) makes it diff icult to lute long span bridges

◦Residual cement is more diff icult to remove.◦Not as strong as Zn/Po.◦Shows plastic deformation, so unsuited to high

load areas

Manipulation◦The cement should be mixed on the surface that

does not absorb l iquid; hence, a glass slab is preferred to treated paper pads.

◦The liquid should not be dispensed prior to mixing because it tends lose water

◦The powder is rapidly incorporated in bulk as two increments into the l iquid in large quantit ies

within 30 seconds using a Glass slab and stainless steel spatula.

◦Cooling the slab increases the setting time.◦Should not be disturbed in rubbery stage as wil l

pull from margins

This cement is recommended for single units and short

span fixed partial dentureIt is also recommended for

hypersensitive teeth and when preparations come close to the pulp..


Composit ion: alumino-f luorosil icate glass and weak polyacrylic acids

Adhesive, and reports of reduced microleakage

Early exposure to water signif icantly reduces ult imate strength

Low cement f i lm thickness (25 to 35µm(Does not appear to be more irr i tant to

pulp, as earl ier reports suggested

Advantages◦Cement has adhesion to enamel and dentin (low bond

strength to teeth(.

◦Exhibits good biocompatibi l i ty (no pulpal protection is required(.

◦I t releases fluoride (anticariogenic effect(.

◦Easy to mix , good resistance to acid dissloution.

◦Set cement is translucent (advantage when used with porcelain labial margin(.

◦Mechanical properties are comparable with zinc phosphate cement (medium-high compressive

strength 90 to 140 MPa, T.S 6 to 8 MPa(.

Disadvantages◦long term sensit ivity can result i f tooth is over

dried.

◦High susceptibi l i ty to moisture contamination. during setting, (more recent formulations may

be less susceptible than the earlier products(.

◦Slow setting, possible pulp irr itation.

◦variable adhesive characteristic.

◦Residual cement is more diff icult to remove.

These cements are excellent

for general prosthodontic use. Fluoride release may be

beneficial for some patients. Avoid using glass ionomer with

hypersensitive teeth.


Resin modif ied polyalkenoate cement (Mixture of resin and glass ionomer

powder(Combines the strength and insolubil i ty of

resin with the f luoride release of glass ionomer.

Manufacturers recommend their use for all-metal or ceramo-metal crowns and bridges, , but not for posts (risk of expansion induced

root fracture(Not recommended for al l-ceramic

restorations, because delayed cement expansion can result in ceramic fracture

Working t ime can be lengthened by using refrigerated l iquid, mixing on cold slab or decreasing powder-l iquid rat io. Higher temperature shorten working

t ime.Use microetching to prepare internal

metal surfaces for increased bonding.Remove excess cement before f inal set.Use desensit izing l iquid to reduce

possible sensit ivity without dramatically affecting bond to tooth.

Zinc Oxide Eugenol (ZOE) was developed by Dr. J. Foster Flagg in 1875 (3). Zinc oxide powder reacts with water, forming zinc hydroxide. Zinc hydroxide then reacts with the eugenol to make zinc eugenolate. Zinc eugenolate is a very soluble cement because it can hyrolyze back into zinc hydroxide and eugenol (i.e. a reversible reaction

ZOE cement is relatively weak in strength when compared to other cements. Orthoxybenzoic acid can be added to the eugenol and alumina or poly (methyl methacrylate) can be added to the powder to

increase the cement’s strength. This cement is known to have an obtunding effect on the pulp . Because of its weak strength and high solubility, zinc oxide eugenol cement may be questionable as a permanent luting agent.

Fynal (Dentsply/Caulk) is a reinforced zinc oxide eugenol cement

This cement may be used on very sensitive teeth that have excellent

retention/resistance form.


Examples of resin cements include PANAVIA (Kuraray Co., Ltd.) Calibra (Dentsply/Caulk), and Variolink (IvoclarVivadent, Inc.).

Composition: Bis-GMA resins and other methacrylates .

Available in a wide range for formulation. These can be categorized

on the basis of polymerization into :(Chemical-, photo- and dual-cure(

Adhesion to enamel by micromechanical retention to dentine

by more complex penetration of hydrophil ic monomers through

collagen layer overlying partial ly demineralized apatite of etched

dentine

Condit ioning: removal of smear layer, and demineralize top 2-5 microns

Primer: wetting agent such as HEMA (Hydroxy Ethyl Metacrylate ) applied;

bifunctionality enables hydrophil ic bond to dentine and hydrophobic bond to

adhesiveAdhesive cement: e.g. 4-

META(Methacryloxy Ethyl Ttimil l i t ic Anhydride) penetrates into tubules

Polymerization shrinkage remains a problem

The manipulative techniques may be very different with different

brands of resin cements.Shade of veneers can be modified

by the shade of the luting agent Colour-match try-in pastes are

available to facilitate selecting the best cement shade.

Advantages: ◦high strength,

◦low oral solubil i ty.

◦ high micromechanical bonding to prepared enamel, dentin, al loys and ceramic surfaces.

Disadvantages:

◦The need for meticulous and crit ical technique,

◦More diff icult sealing and higher f i lm thickness than tradit ional cements,

◦Possible leakage and pulp sensit ivity,

◦Diff iculty in removal excess cement

Resin cements are suitable for luting porcelain, cast ceramic, and composite

restorations and recommended for teeth

that have inadequate retention/resistance after preparation


Zinc oxide –eugenol: powder zinc oxide, the l iquid is purif ied eugenol.

Low compressive and tensile strength(7-40 MPa, 1000-6000P psi(.

Film thickness of 40 µmHigh solubil i ty about 1.5%, l i t t le

anticariogenic actionAbtudent effect on the pulp, good sealing

abil i ty and resistance to marginal penetration.

Reinforced zinc oxide-eugenol cements: by adding EBA, alumium oxide and PMM.

Primary purpose of lut ing cement: to seal tooth-restoration interfacial space

Choice of luting agentType of restoration: conventional casting

or adhesive restoration

After cleaning the preparation, cavity varnish should be applied if a

non-adhesive cement like zinc phosphate is to be used.

Oxalate treatment of the tooth surface can be done to reduce

dentin sensitivity.

The casting should be cleaned by sandblasting with 50 µm alumina or by steam, fol lowed by ultrasonic or organic cleaning.

Next the operatory site is isolated with cotton rolls.The cement should be mixed to a lut ing consistency.A thin coat of cement should be applied on the internal surface of

the casting.The tooth surface is dried and the prosthesis is inserted with a

firm, rocking dynamic seating force. A static load wil l lead to incomplete seating. Excessive force may lead to fracture.

Next the margins of the retainers are examined to verify the f i t of the prosthesis.

Excess cement should be removed with an explorer. Floss can be used to remove the excess cement in the inter-proximal surface.

Occlusion should be checked with Mylar shim stock or articulating paper.

The patient should be advised to avoid loading for the first 24 hours.

Pdr1.2mg+Lq0.6ml

Viscosity of the cement.Morphology of the restoration.Vibration.Seating force.Venting.

Clean tooth and isolate. Do not use compressed air. I f tooth is dry, moisten

with a wet cotton roll.Excessive air drying of the preparation may

cause post-cementation sensit ivity.Seat casting, then clean up excess cement

after it hardens.I f patient has sensit ivity, delay f inal

cementation for 2-3 weeks.

Fluff powder before dispensing. Hold liquid bottle vertically, and release each drop slowly to ensure

equal size drops.For any powder/liquid cement, incorporate the

powder thoroughly. Insure mix is homogeneous.Load the crown evenly with cement.Place crown cement-side done on your palm for the

dentist to pick up and seat on the tooth.As the cement loses its gloss and start to set, it will

have a stringy, non-sticky consistency. Start removing excess cement before it hardens.

After removal of excess, use a piece of knotted floss and run it through the interproximal areas to remove

remnant cement.Instruct patients to wait 1 hour after cementation.

Clean tooth.Rinse and dry – do not desiccate the tooth.Powder is sensitive to moisture – keep container

tightly sealed.Fluff powder before dispensing.Make sure tip of liquid vial is clean before

dispensing.Dispense liquid form vial held vertically to ensure

uniform drops.Mix all powder into liquid for 20-30 seconds on a

small area of mixing pad.

The patient is asked to exercise all oral functions and awareness should be created regarding the init ial

discomfort.Sudden impact forces should be avoided in the

restored area, e.g. bit ing on a nut or metall ic object.Maintenance:

Oral hygiene procedures with special attention to use of f loss, inter-dental brushes in the concerned area.

De-sensit izing tooth paste or mouth wash can be used if there is sensit ivity.

The patient is advised to report immediately if there is pain.

Regular recall visits for review.

A resin-based desensitizer can be placed on the prepared tooth prior to cementation

to decrease the potential for post cementation sensitivity when using zinc phosphate or glass ionomer cements.

These desensitizers should not adversely effect crown retention

Post-cementation appointment (within a week to 10 days(

Periodic recall – patients with cast restoration are recalled at least every six

monthsPatients with extensive fixed prosthesis

combined with advanced periodontal disease needs more frequent recall

appointments.

SummarySummaryIndications and contraindications for luting agent types

Restoration Indicated Contraindicated

Cast crown, PFM crown, fixed partial denture 1,2,3,4,5,6 -

Pressed ceramic crown, ceramic inlay, ceramic veneer, resin bonded FPD

1 2,3,4,5,6

Patient with history of post-treatment sensitivity 3,6 1

Crown or FPD with poor retention 1 2,3,4,5,6

Cast post and core 1,2,4,5 3,6

Key:1=Resin cement 2=Glass ionomer 3=Reinforced ZOE 4=Resin reinforced glass ionomer 5=Zinc phosphate 6=Zinc polycarboxylate

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