cementation in Fixed prosthodontics

Cementation in Fixed
Prosthodontics
BY :
ABDEL RAHMEN M. ABDEL HAMEED

Content
Clinical importance
Bonding mechanisms
Classification of luting
cements
Ideal criteria of luting
cements
Cement selection
Cementation
Special consideration:

Bonding Mechanisms
Mechanical bonding
Molecular Adhesion
Micromechanical
bonding

Molecular Adhesion
 Molecular adhesion include the use of chemical
bonding between tow materials. Such as chemical
bonding, occur between the COOH group of the zinc
polycarboxylate and glass ionomer (GIC) cements and
the tooth structure.
 Silane coupling agent is another example for molecular
bonding mechanism

Micromechanical bonding
 This mechanism use the microstructure of the tooth structure to provide retention.

 The bond strength of micromechanical bonding mechanism sometimes
exceed the cohesive bond of enamel.
 Ceramics can be etched with hydrophloric acid and silanated, before
using resin cement with it. Metals also can be prepared by electrolytic
etching, chemical etching or sandblasting before using the resin cement
with it.

Classification of luting cements
According to the
duration in clinical
performance
definitive
Provisional
According to
reaction
mechanism
acid base
reaction
polymerization
reaction

Ideal criteria of luting cements
 Physical properties
 Biocompatibility
 Sealing and Anticariogenic Activity
 Adhesion

 Mechanical properties
 Fatigue strength
 Fracture toughness
 Elastic Modulus
 Wear

 Handling and radiopoacity
 Ease of use
 long working time
 short setting time
 Radiopoacity
 Esthetic

Cement selection
Zinc phosphate cement
Zinc polycarboxylate
cement
Glass Ionomer cements
Zinc oxide eugenol
cements:
Resin cements
Resin modified glass
ionomer

 Compressive strength (st): 96-110 Mpa
 Tensile st: 9.3 Mpa
 PH during cementation: 3.5
 Film thickness: 10-20 um

Zinc polycarboxylate cement
 Compressive st: 50-80 Mpa
 Tensile St: 7-10 Mpa
 Bond strength to tooth structure: 9 Mpa
for Enamel and 3.3 Mpa for Dentin.
 PH during cementation: 4.8
 Film thickness: 13-20 um

 Compressive st: 127 Mpa
 Tensile st: 8Mpa
 Bond st to tooth structure: 9 Mpa for enamel and 3 Mpa for
dentin
 Film thickness: 9.5 – 16 um

 advantages
 fluoride
 Bond to tooth structure
 good esthetic properties
 less soluble than zinc phosphate cement
 GIC is 65% more retentive than zinc phosphate cement.

 disadvantages
 high acidity
 sensitive to both moisture and dehydration
 . GIC is translucent

Cement selection
Zinc polycarboxylate
cement
Zinc oxide eugenol
cements
Resin cements
Resin modified glass
ionomer

Resin cements
 Compressive st: 200-250 Mpa
 Tensile st: 40-50Mpa
 Film thickness: 25 um
 Solubility in water: Insoluble

 Resin cements are composed of organic matrix such as BISGMA or UDMA
and inorganic fillers
 Advantages
 high mechanical properties
 good seal abilities
 good bond strength
 no solubility
 excellent esthetic

 disadvantages
 polymerization shrinkage
 pulpal irritation
 difficulty of removing the hardening
excess cements.

Classification of resin cement
According to
the adhesive
scheme
Self-etching Self-adhesive
Total etching
According to
the mode of
polymerization
Chemical cure Light cure Dual cure

Total etching resin cements
 use three step bonding technique
 Acid etching
 Bonding
 Cement application

Self-etching
 The bonding agent is applied directly to
the tooth structure and cured, and then
the resin cement is applied.

Self-adhesive resin cements
 The adhesive resin cement can be applied
directly to the tooth structure. It provide the best
retention with dentin.

Resin modified glass ionomer
 Compressive st: 150 Mpa
 Tensile st: 25-35 Mpa
 Film thickness: 20 um
 Resin modified glass ionomer
combine the strength and the
insolubility advantages of the resin
cements and the fluoride release of
the GIC

Cementation
Cementation with Zinc
phosphate cement
polycarboxylate cement
Cementation with glass
ionomer cements
Cementation with resin
cements

Cementation with Zinc phosphate
cement
 tips for cementation :
 Complete isolation is necessary during the whole
process.
 Vital teeth ---> two layers of varnish or bonding agent
should be applied first.
 Non-vital teeth ---> No need for varnish.
 Liquid/Powder Proportions: six drop of liquid for each
crown.
 Do not dispense the liquid until just before mixing.

 Divide the powder in small increments each
of 3 mm thickness.
 Mixing time is 10-20 seconds for each
increment.
 Mix in circular motion.
 Mix over wide area of the glass slab
 introduce the powder slowly in to the liquid
 check the consistency
 Bruch the cement inside the fitting surface

 grooves, pins, and inlays ---> fill them before
seating the restoration
 If necessary use the retraction cord in the
sulcus.
 seat the restoration
 ask the patient to close over a plastic wafer
 Leave the cement to fully set then remove the
excess.

polycarboxylate cement
 Tips for cementation:
 Isolation
 wash the restoration and clean it with alcohol
 sandblast the fitting surface
 coat the outer surface with petroleum
 Powder/Liquid Proportion : according to
manufactures instructions
 working time: 30 seconds

 brush the cement inside the restoration, seat
the restoration, ask the patient to bite over
aplastic wafer
 setting time: 3 minutes
 Remove the excess either before or after the
cement become rubbery.

Cementation with glass ionomer
cements
 tips for cementation
 isolation
 coat outside the restoration with petroleum
 Clean the tooth with brush and pumice. don’t
use acid etch for this step
 Don not use varnish
 Powder / Liquid proportions : one scoop of
powder/ two drops of liquid
 working time: 60 seconds
 setting time : 3 minutes

 mix rapidly until the mix become creamy
 capsule form is now available in the market
 Brush the restoration with the cement; seat the
restoration, ask the patient to occlude over the
plastic wafer.
 Wait until the cement become brittle but before
complete setting and remove the excess
cement.
 Coat the crown margin with varnish or petroleum

Cementation with resin cements
 Tooth preparation :
 isolation ( rubber dam is a must)
 clean the tooth with pumice and brush, clean and
dry
 if total etching system is used :
 apply the acid etch ( phosphoric acid 37% ) 30
seconds for enamel and 10 seconds for dentin
 wash and dry ( don’t dissipate dentin)
 apply the bond with brush, wait for 1 minute, cure for
20 seconds

 if self-etching system is used
 apply the self-etching bond , wait for 1 minutes and
cure
 If total etching system will be used the tooth not need
any preparation more than cleaning with brush.

 treatment of the fitting surface of the restoration :
 The fitting surface of the restoration is treated
before receiving the resin cement by two ways
 Roughening the surface to increase the surface
area and create a microspores In the restoration
surface
 Increase the wettability of the restoration surface
with silane coupling agent.
 Roughnining of the fitting surface can be
achieved by various techniques depending on
the type of the restoration.

Special consideration:
Cementation of ceramic
restorations
Bonding of resin to
zirconia:
Cementation of posts
Cementation of partial
coverage restoration
Cementation of the gold
alloy:

Cementation of ceramic restorations
 tooth preparation
 restoration preparation differ according to the type of the ceramic material:
 Feld spathic porcelain ( HF + S )
 Lucite reinforced ceramics (IPS Empress): ( sand + S )
 Lithium disilicate (IPS Emax( ( Sand + HF + S )
 Zirconia
 Lava ( Silica )
 Cercon ( Silica + MDP )
 other types such as IPS Emax zircad and Ketana (Phosphoric acid monomer containing primer)

Bonding of resin to zirconia:
 sandblasting and silanation of zirconia
 Plasma spraying
 Porcelain particles infusion

Cementation of posts
 Metallic posts
 Fiber posts

Cementation of partial coverage
restoration

Cementation of the gold alloy:

cementation in Fixed prosthodontics

cementation in Fixed prosthodontics

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