dental cement, 517
TRANSCRIPT
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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).
21 3
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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