dental cement, 517

8/2/2019 Dental Cement, 517

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Dental Luting Cement

Dr: MohD Al-Moaleem


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1- A binding element or agency used as a substance to make objects adhere to each other.

2- A material that, on hardening, will fill a space or bind adjacent object.

Dental cement provide bond that prevent the restoration from removal, fill the micro-space

between the restoration & tooth (dose not contribute to the retention ?).

Function of the dental cement:

To secure the retention of the restoration to the tooth.

To seal the gap against fluids and bacteria from the oral cavity.

To act as insulting barrier against thermal and galvanic effect.


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Adhesion to the tooth structures

Biological compatibility with the pulp

High mechanical Properities

Low viscosity and high flow

Wetting Low film thickness (


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Factors increasing cement spaces:

1- Thermal and polymerization shrinkage of the impression materials

2- Use of a solid cast with individual stone dies

3- Use of internal layer of soft wax4- Over use of die spacer

5- An increase in the expansion of the investment mold

6- Removal of he metal from the fitting surface.

Factors decreasing cement spaces:1- Use of resin or electroplate dies

2- Use of alloy with higher melting range

3- Reduced expansion of the investment.


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Factors affect the mechanical interlocking bond:

1- Geometrical relation of the preparation (retentive qualities, surface area, taper,

length of preparation)

2- The biophysical factor related to casting (fitting accuracy, modulus of elasticity of

the metal, surface texture of the inner surface of the restoration)3- Mechanical property of the luting agent (compressive, tensile, shear strength and

film thickness)

4- Differences in the coefficient of thermal expansion (tooth, restoration & cement)


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Bonding mechanism of dental cement:

Non-adhesive or mechanical in which cement extended into small irregularities of the

adjoining surface sandblasting and roughening of cast (Zinc phosphate) . Micromechanical: Resin cement holding the restoration by penetrating into small surface pit

Molecular adhesion it is true adhesion is the molecule ions exerted between the surface of

bodies in contact (Polycarboxylate, GI, RMGI).

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Types of dental luting cement

Zinc oxide and egenol ( conventional & modified) -------------- temporary.

Zinc phosphate cement

Zinc polycarboxylate cement permanent

Glass ionomer cement ( conventional & resin modified)

Composite resin cement ( conventional & adhesive).


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Reinforced zinc oxide and eugenol

1- Adhesion: mechanical

2- Biological compatibility: palliative

3- Mechanical properties: low

4- Solubility: soluble

5- Working time: short can be increased by adding of water?6- Translucency: not translucent

7- Anticarogenic effect: no

8- Remove the excess: difficult

9- Film thickness: high film thickness.

Mainly used for temporary cement

Deterioration faster than other cement in patient mouth

Coat the patient tounge, cheek adjacent to teeth to improve clean-up

Combined with EBA and reinforced with AL oxide to improve mechanical properties to used

as permanent cement (type II).


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1-Adhesion: mechanical

2- Biological compatibility: irritant

3- Mechanical properties: high

4- Solubility: high soluble (hydrophilic)

5- Working time: long 5 min6- Translucency: not translucent

7- Anticarogenic effect: no

8- Remove the excess: easy

9- Film thickness: 25 micron.

Zinc phosphate cement

Post-operative sensitivities due to Initial irritation to pulp (PH 2-305) reduced gradually

after setting to (6.5 at 24 hours)

Cementation of conventional crown and posts with good retentive features

Low hardness

No bond with tooth so need abrading of the cast by sandblasting In multiple restorations, working time can be extend by incremental and cool slab mixing.


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Zinc Polycarboxylate cement

Molecular bonding to tooth substance (2MPa)

Low post-op sensitivities

Low hardness and not resist to acid dissolution

useful to retain un-retentive provisional crowns.

1- Adhesion: chemical and mechanical2- Biological compatibility: good and no adverse effect on pulp (ph 4.8) and lesser penetrationthrough dentinal tubules because large molecular weight of polyacrylic acid3- Mechanical properties: high tensile strength then zinc phosphate but less in compressive

4- Solubility: yes5- Working time: very short 2.5 minutes6- Translucency: no7- Anticarogenic effect: no8- Remove the excess: difficult9- Film thickness: 25 micron.


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Glass ionomer cement

1-Adhesion: chemical by molecular bonding to tooth substance and mechanical (3-5MPa)2- Biological compatibility: good but may cause some post operative sensitivity.3- Mechanical properties: high with minimal dimensional changes and better compressive

strength4- Solubility: yes sensitive to water and it is contamination with moisture5- Working time: moderate 3.56- Translucency: yes, limited application to ceramics7-Anticarogenic effect: yes, with fluoride release so crown cementation with high caries index8- Remove the excess: easy9- Film thickness: 20 micron

10- Some reported with sensitive cases due to lower PH

GIC, a polyacrylate based translucent cement, was introduced to

dentistry in 1972. It attempts to combine the advantages of both

silicate and polycarboxylate cements.


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RMGI

Molecular bonding to tooth substance or good compressive 85-126 MPa and

tensile strength (13-24 MPa) , high bonding strength

Fluoride release

Low solubility or resistant to water solubility

Good working time

Reduced post-op sensitivities (effect on dental pulp)

Hybrid with light curing resin (self cured is the most used)

Translucency

Any restoration with low retentive features

Reported cause of fractures of porcelain because expansion after water absorption.


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Resin cement

1-Adhesion: conventional mechanical

adhesive mechanical and chemical

2-Biological compatibility: irritant

3- Mechanical properties: excellent

4- Solubility: low

5- Working time: conventional short

adhesive controllable

6- Translucency: yes

7- Anticarogenic effect: no8- Remove the excess: conventional difficult

adhesive : easy

9- Film thickness : conventional high

adhesive 19 micronHigh adhesive quality (18-20MPa)

RetentionHigh hardness

All metal, ceramic , composite(indirect) with self, light and dual cured

Occa. Post-op sensitivities

Less viscosity than restorative material


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Comparison of available luting agents


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Cementation techniques and pre-treatment

Zinc phosphate

Polycarboxylate

Glass ionomer

RMGI cement

Resin cement

Conventional

Adhesive


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Pre-treatment procedure


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Pre-treatment procedure


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Advantages of conventional cement

Easy handling

Moisture tolerance

No pre-Tx steps

Routine for metal base

Cementation techniques


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Advantages of resin cement

Excellent mechanical properties

High bond strength with pre-Tx step

High aesthetics/translucency

Suitable for Ceramic, Porcelain, Reinforced Composite and Metal.


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Selection of luting cement depending on:

Mechanical properties of cements

Biological consideration

Bonding mechanism strength

Prepared teeth geometry (over prepared tooth)

Dissolution in water Film thickness

Type of restoration (inlay, partial veneer or full crown)


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Selection of luting cement? EXAMPLES

Long bridge: (High mechanical property, long working time and adhesive property)GI, zinc phosphate or adhesive composite.

Patient with high caries index: (cement with fluoride release) GI or adhesive resinPanavia f.

Deep preparation (cement palliative and non irritant to the pulp) polycaroxylateand reinforced ZOE.

Cementation of free metal restoration: (cement with high translucency, strengthand bond to booth restoration and tooth) adhesive resin.

Cementation of post: (high flow, adhesive and strength) GI, adhesive resin or zincphosphate.

Cementation of resin bonded bridge or questionable preparation: (cement withhigh strength, bond to both restoration & tooth and insoluble) adhesive resin.


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Cementation of a restoration to a core: Requirement, adhesion to the coreComposite core----------------------- composite resin

Glass ionomer---------------------------- glass ionomer

Amalgam-------------------------------------all cement

Cast gold--------------------------------- best is zinc poylcarboxylate, and resin cement

Non precious inlay-----------------resin, GI, poylcarboxylate

Post cementation: (high flow, adhesive and strength) GI, adhesive resin or zinc phosphate


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Seven Boo-boos

1- Over contouring

2- No proximal contact

3- Open or over finished margin

4- No occlusal contact5- Perforation while adjusting the occlusion

6- Occlusion left to high

7- Cement left below the gingiva.

Recommended reading:

Fundamentals of Prosthodontics (third edition) Herbert T. Shillinburg, Sumiya Hobo, Lowell

Whitsett, Richard Jacobi and Susan Brackett, 1997, Quintessence Publishing Co PP. 400-418

dental cement, 517

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