Fixed prosthodontic lecture

For Dr.Amr Mahrous

Cementation Procedures
Lecture outline:
ADA classification of dental cements:
Uses of dental cements:
Temporary cementation:
Final Cementation
ADA classification of dental cements:
O Type I (Luting cement):
Fine grained luting cements for casted restoration.
O Type II (Liner & bases):
Medium grained thermal insulating cements.
Uses of dental cements:
1- Luting agents
- Restorative (inlays, crown, bridges)
a. Interim cements (temporary)
b. Final cements (permanent)
- Temporary restoration.
- Orthodontic brackets.
2- Bases & liners
Temporary cementation:
O After try-in send the crown for glazing then temporary cementation.
O Why temporary cementation:
1. Too see performance of the crown.
2. Too see if there is premature contact.
3. Too see if there is food impaction.
4. Too see if there is impinging on gingival (clinically by blanching), this occurs usually
below pontic on the crest of the ridge.
5. Too see if the patient accepts the esthetic.
6. Too see the oral hygiene of the patient (follow oral hygiene instructions).
O Requirements of temporary cements:
1. Easily application.
2. Biological compatible.
3. Easy to mixed.
4. Easily removed (no residue on the prepared tooth).
5. Palliative effect on the pulp.
6. Not fluid in consistency.
7. Set hard rapidly after adequate working time.
8. Excess cement can be removed rapidly.
9. Hold the restoration for the required time.
10. Restoration can be cleaned & removed easily for rinse.
O Advantages of temporary cementation & restoration:
1. Decrease post operative pain.
2. Reduce the incidence of pulpal involvement.
3. Bridge can be further removed for adjustment & modification.
4. Decrease post cementation symptoms of hypersensitivity.
O Examples:
-Tembond cement. -Mirage bond cement. -ZOE for temporary cementation.
O Types of temporary cements:
Eugeonol Non-eugenol
' Advantages:
1. Very good marginal seal.
2. Biological.
3. Obtundant effect on pulp.
' Disadvantages:
1. Retard polymerization of acrylic & composite.
2. Discoloration of acrylic of temporary bridge.
3. Contamination of the surface of the tooth
interferes with bonding.
4. Softening of composite build up.
' Used with:
1. Bond.
2. Composite core.
3. Temporary acrylic bridge.
Final Cementation:
O Ideal requirement of permanent cementation:
1. Sedative to the tooth structure.
2. Insoluble in the oral fluid.
3. Strong enough to withstand functional forces.
4. Good marginal seal.
5. Easy to mix, manipulate & apply.
6. Thin film thickness to allow the maximum seating of the restoration.
7. Adequate working time.
8. Mixed cement shouldnt flow from the restoration.
9. Non-irritant to dentin.
O Selection of the cement according to:
1. Retention requirements & preparation design (long span bridge differs from one crown).
- For example, More retention is needed with the following
*Over-tapered *Over-reduced *Long span bridge *Heavy lifting force
*Tilted abutment *Not enough # of abutment
So we must select cement give more retention..
2. Type of the restoration (post, crown, Maryland Bridge=resin bonded bridge).
- In post & core we need low viscosity cement to allow escape of excess cement.
- Also with long crown.
- ^ # of abutment teeth need cement with long working time to allow adequate time
for apply the cements before setting of the cement.
3. Anti-cariogenic properties.
- To resist caries.
- Patient with high caries risk, badly destructed teeth, gingival recession, and exposed
roots.
- G.I, resin cement, polycarboxylate cement fulfill this property by fluoride release.
O Permanent cementation agents:
Zinc phosphate cements.
Zinc silicophosphate cements.
Resin forced zinc oxide eugenol.
Zinc polycarboxylate cements.
Glass ionomer cements.
Resin cements.
Zinc phosphate cements:
A
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P
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:
-Zinc oxide + phosphoric acid.
-Reaction: Acid base mix- chemical reaction.
-Film thickness: 25 micron
-Mode of adhesion: by the mechanical interlocking of the set cement to the surface of
the metallic restoration of the tooth structure which are some what rough & serrated.
B
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M
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:
-Using a cooled, dried, clean, glass slab & spatula because of the exothermic reaction &
mix over wide area to dissipate the heart.
-Mixing is started by adding small amount of powder (bit by bit) to the liquid using a
rotary motion on a wide area to perform a uniform mix & +air bubbles.
-Adding powder bit by bit working time
-While mixing try to scratch the slab to air bubbles in the mix.
-The correct mix is of creamy consistency.
-Creamy consistency shown by rising the spatula inch from the slab.
-If the slab was not clean contamination could occur accelarate setting & prevent
insertion of the crown.
-Mix on dry slab because its sensitive to hydration(H2O)
C
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P
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&

u
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:
-It has a long working time can be used with long bridge.
-Low viscosity.
-Irritant to the pulp because the molecular size is small can diffuse to the pulp.
-Used with long span bridge with multiple retainers.
-Put varnish to seal dentinal tubules.
D
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P
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:
-In deep cavities, pulp protective means are required e.g. varnish
-The cement line should be protected for the 1
st
24 hours to prevent cement dissolution
by e.g. varnish
Zinc polycarboxylate cements:
A
.

P
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:
-Polycarbonate cement= ZO+polyacrylic acid
-Reaction: Acid base chemical mix
-Film thickness: if correctly mixed, it will be 25micron or less
-Mode of reaction: truly adhere to the tooth structure, because the polyacrylic acid
chelate the calcium of the tooth (adhere to the enamel more than dentin due to higher
mineral content).
-Sometimes has an anticariogentic property (in some new commercial products).
-Less soluble than ZPC.
-More biologic due to large molecular size cant diffuse into dentinal tubules no
irritation.
-No postoperative pain.
-Very good retention.
-Rapid setting time.
-Disadvantages:Overy rapid settingOhigh viscosity after mixing due to evaporation of
liquid may prevent complete setting of the crown.
-Contraindicated with Opost & coreOlong span bridge with multiple retainers due
to high viscosity.
B
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M
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:
-Using glass slab cooled or non-absorbing paper & spatula.
-All of the powder is incorporated into the liquid in 2 or 3 large increments using rapid
spatulation for 30 seconds only because after 30 seconds the mix becomes dull no
retention & no bonding.
-Start mixing by circular motion.
-Dont leave it in the air for long time not to be dull & evaporation of the liquid
discarded.
-Before taking the material, shake the container to be sure that all the material is
dispersed.
-Capsules are preferred Opre-measured (correct ratio)O No need for shaking.
D
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P
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:
-Cooling the glass slab slows the chemical reaction & therby provides a little longer
working time, which quit short.
-Never store the liquid in a refrigerator, the low temperature causes the liquid to thicken
or become gel.
-Avoid evaporation of H2O from the liquid (otherwise there will be vescosity).
-For optimum adhesion to tooth structure & to the metal casting, the surfaces should be
thoroughly clean & dry.
-Shake the container of the powder before use to be sure that the content are mixed
well, so capsules are preferred because:OPre-measured (accurate & constant
composition)ONo need for shaking.
N.B: cement line: is the film of cement found @ the junction between the tooth
structure to the finish line & the margin of the restoration.
Resin forced zinc oxide eugenol:
Can be used as permanent cement by adding fillers (ethoxy benzoic acid) to strength.
Have less retention, so its used in Olong preparationOWide tooth surfaceObulky retentive
preparationOin sensitive teeth.
Glass ionomer cements:
A
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P
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:
-This is an alumino silicate glass powder & polyacrylic acid.
-Polyacrylic chelation more retention.
-Reaction: Acid base (chemical)
-Film thickness: about 25micrometer, Film thickness: cement at the fitting surface of
restoration.
-Solubility: Less soluble than ZPC & Zinc poly carboxylate cements.
-Has an anticariogenic effect due to fluoride release.
-Its very soluble in its early stage sensitive to early attach by saliva varnish or
vasline can be used to protect the margin.
B
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M
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:
-The same as with zinc polycarboxylate cement.
-N.B:The cement line should be protected during the 1
st
24 hours from dissolution (by
varnish).
-ZPC is indicated for long span bridges due to its high strength.
-use conditioner to clean tooth surface & enhance bonding to Ca++ of tooth with
cement.
D
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P
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:
-Susceptible to be attacked by water during its setting so a varnish , dentin bonding or
glaze should be applied on the cement line after cementation (delayed setting time).
-Wait for the cement to harden enough before removing the excess because in early
stage of setting it is rubbery in consistency & may pull form the fitting surface
deficient cementation.
Resin cements:
A
.

T
y
p
e
s
-polymethyl methactylate
-Bis-GMA
-4-META
-Panavia-Ex (phosphate ester)
B
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P
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-Insoluble
-Film thickness: 25micrometer or more
-Good adhesion by micromechanical retention
-Good retention
-Good comprehensive strength
-Controlled working time can be used with long span bridges.
-Used with porcelain , porcelain laminated & resin bonded bridges.
C
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M
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According to the type of resin.
D
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P
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-Need pulp protections in deep cavities.
-The excess cement flash should be removed immediately upon seating & avoid pulling
the excess in the rubbery stage or it may pull from the fitting surface.
If composite restoration use composite cement.
O General cementation procedures:
Casting preparation:
- The casting fitting surface should be thoroughly clean & dry by OSand blasting
OUltrasonic cleaning OCleaning by stem under pressure.
- Micro-abrasion of the fitting surface may be required to ^ the retention @ the cement-
casting interface.

Mouth preparation:
- The teeth should be clean & dry (use pumice + brush to remove any remnants of
temporary).
- Cotton rolls & saliva ejector isolation & if not possible, use rubber dam isolation.
- N.B: Sometimes anti-sialogouge is necessary to help control excessive salivation.
Cement application:
- A thin layer of properly mix cement is applied to the internal aspect of the casting.
- With intra-oral preparation feature, the cement should be introduced into them prior to
seating the restoration e.g. (we may use lentulo spiral into holes or post holes).
Seating the restoration:
- Forceful finger pressure in a BL direction adequately seat most restoration.
- Check complete seating by checking the cast margins by an explorer.
- Biting forcefully & continuously on an orange wood stick (like tongue depressor) can be
helpful in seating the restoration.
- Removal excess cement.
- Final inspection.
N.B:
- You have to check the occlusion of the patient directly after application to avoid any
failure & in this stage you still can manage to remove the restoration & you my need to
cut it.
Strawberry