Luting cements/ dental courses/endodontic courses

LUTING CEMENTS &LUTING CEMENTS &
LUTING PROCEDURESLUTING PROCEDURES
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

CONTENTS:
• INTRODUCTION
• IDEAL REQUIREMENTS
• TYPES OF COMMERCIALLY
AVAILABLE LUTING AGENTS
-- SHORT TERM CEMENTATION
1. ZINC OXIDE EUGENOL
-- LONG TERM CEMENTATION
1. ZINC PHOSPHATE
2. ZINC POLYCARBOXYLATE
3. GLASS IONOMER
- RESIN MODIFIED GIC
- COMPOMER
4. RESIN CEMENTSwww.indiandentalacademy.com

• PHYSICAL & BIOLOGICAL PROPERTIES
OF LUTING CEMENTS
• CHARACTERISTICS OF ABUTMENT
PROSTHESES INTERFACE
• PREPERATION OF THE RESTORATION &
TOOTH SURFACE FOR CEMENTATION
• PROCEDURES FOR LUTING PROSTHESES
• POST CEMENTATION PROCEDURES
• MECHANISM OF RETENTION
• DISLODGEMENT OF PROSTHESES
• INDICATIONS FOR DIFFERENT
RESTORATIONS
• COMPARITIVE STUDIES
• SUMMARY
• REFERENCES.www.indiandentalacademy.com

INTRODUCTION
• The word LUTING means use of a moldable substance to
seal a space or to cement two components together.
• Numerous dental prostheses & appliances necessitate
attachment by means of a luting agent like metal, metal-
ceramic, composite & ceramic restorations, provisional
acrylic restorations, laminate veneers for anteriors, ortho-
appliances & pins and posts used for retention of
restorations.
• They provide link between supporting restoration &
prepared teeth by acting as adhesive.

IDEAL REQUIREMENTS
• According to mechanical, biological, esthetic &
working properties point of view:
– Should provide a durable bond between 2
dissimilar materials
– Should possess favourable compressive
strength & tensile strength
– Should have sufficient fracture toughness to
prevent dislodgement as a result of cohesive or
interfacial failures
– Should be able to wet the tooth & restoration
– Should exhibit adequate film thickness &
viscosity to ensure complete seating.www.indiandentalacademy.com

• Should be resistant to disintegration in oral
cavity
• Should be tissue compatible
• Should be caries & plaque inhibitant
• Should demonstrate adequate working &
setting time
• Should be resistant to micro-leakage
• Should be wear-resistant
• Should have colour stability for esthetic
purposes
• Should have radio-opacity to detect cement
line or over-hangs & caries.www.indiandentalacademy.com

TYPES
• Short term cementation:
– Zinc oxide eugenol
• Long term cementation
1. ZINC PHOSPHATE
2. ZINC POLYCARBOXYLATE
3. GLASS IONOMER
- RESIN MODIFIED GIC
- COMPOMER
4. RESIN CEMENTS

• Traditional cements can be used for
conventional cast crowns or FPDs, but
when adhesion is required like in ceramic
inlays or resin bonded restorations,
adhesive resins are required
• Ultimately success is attributed to excellent
adaptation between casting & prepared
tooth

ZOE CEMENT
• Either available in powder & liquid form or
as a 2 paste system
• TYPES:
Acc to ANSI/ADA specification No.30 classified
as Type I, II, III, IV
Type I & II are used for temporary & long term
cementation respectively.

COMPOSITION
• Powder
– Zinc oxide 69% principal ingredient
– White rosin 29.3% to reduce brittleness of
set cement
– Zinc stearate 1% accelerator &
plasticizer
– Zinc acetate 0.7% accelerator & improves
strength
– Magnesium oxide added in some powders acts
similar manner like zinc oxide
with eugenol
• Liquid:
– Eugenol 85% reacts with zinc oxide
– Olive oil 15% plasticiser

MANIPULATION
– Type I (Two paste system)
• Equal lengths of accelerator & base paste are
dispensed on a cool glass slab or paper pad.
• The pastes are colored differently
• Mixing should be continued until uniform
colour is achieved
– Type II (Powder & Liquid form)
• P/L ratio 4:1 to 6:1 by weight

• Procedure:
– Bottles are shaken gently
– Measured quantity of powder & liquid is
dispensed onto a cool glass slab or paper pad
– Bulk of powder is incorporated in liquid &
spatulated thoroughly in a circular motion with
a stiff bladed stainless steel spatula for
30seconds
– Smaller increments are then added until mix is
complete

Setting Reaction
• Consists of zinc oxide hydrolysis
• There is subsequent reaction between zinc
hydroxide & eugenol to form a chelate
• Water is needed to initiate the reaction & is also a
by-product which makes the reaction rapid in
humid environment
• Reaction can be also accelerated by acetic acid or
in the presence of high atmospheric temp

• The patients lips & adjacent teeth should be
coated with silicon grease or petroleum
jelly before application of cement as it is
difficult to remove from tissues after setting
• Glass slabs & spatulas should be wiped
clean before cement sets. Oil of orange is
used for this purpose.

LONG TERM LUTING
CEMENTS
• ZINC PHOSPHATE:
– Oldest of luting cements
– Available as powder & liquid in 2 separate
bottles
• Classification acc to ADA specification
No.8
– Type I & II
– Both can be used for luting purposes

Composition
• Powder:
– Zinc oxide 90.2% principal
constituent
– Magnesium 8.2% aids in sintering
– Other oxides 0.2% improves smoothness
(Bismuth trioxide, calcium oxide, etc)
– Silica 1.4% filler, aids in sintering
• Liquid:
– Phosphoric acid 38.2% reacts with ZnO
– Water 36% controls rate of
ionization
– AlPO4 or ZnPO4 16.2% buffer
– Aluminum 2.5%
– Zinc 7.1%www.indiandentalacademy.com

Manipulation
• P/L Ratio- 1.4gm/0.5ml
• Mixing time- 1min 15secs
• A cool glass slab(-10 to 6 deg cel) is used to delay
the setting & allow more powder to be
incorporated before matrix formation occurs
• Liquid should be dispensed just before mixing
• Powder is added in small increments
• Large area is covered during mixing to release the
heat

• Maximum amount of powder should be
added to ensure minimum solubility & high
strength
• Appropriate consistency is attained by
adding more powder. Thin mix has low ph
which deteriorates physical properties

Setting Reaction
• When powder is mixed with liquid, phosphoric
acid attacks the surface of the particles & releases
Zn ions into the liquid
• Aluminum in liquid is essential for cement
formation. It forms a complex with phosphoric
acid,reacts with Zn & produces a Zinc alumino
phosphate gel on the surface of remaining
particles
• Thus the set cement is primarily un-reacted ZnO
particles embedded in the complex of zinc
zlumino phosphate

Control of Setting time
• P/L ratio
• Spatulation
• Mixing the large quantities in increments
• Temp of glass slab
• Water content of liquid
• Adding buffer
• Particle size

ZINC POLYCARBOXYLATE
• First cement system that developed adhesive bond to tooth
structure
• Composition:
– Available as powder & liquid, water settable cement or
pre capsulated P/L system
• Powder:
– Zinc oxide basic ingredient
– Magnesium Oxide principal modifier & aids in
sintering
– Oxides (Bi, Al)
– Stannous fluoride increases strength, modifies
setting time & anti-cariogenic
properties
• Liquid:
– Liqueous soln of poly acrylic acid or copolymer of
acrylic acid with unsaturated carboxylic acid i.e.,www.indiandentalacademy.com

Manipulation
• The tooth structure should be meticulously
clean in order to provide intimate contact &
interaction between cement & tooth (10%
poly acrylic acid soln. followed by rinsing
with water or 1-3% H2O2 can be used)
• The tooth is then dried & isolated
• P/L ratio 1.5:1 by wt
• Mixing is done on cool glass slab or paper
pad
• Powder may be cooled but liquid cannot as
its viscosity increaseswww.indiandentalacademy.com

• Powder and liquid are taken on a glass slab.
Liquid is removed just prior to mixing
otherwise viscosity increases
• Powder is incorporated in large quantities
with a stiff cement spatula & remaining
powder is added to adjust consistency.
• Mixing should be completed within 30-
40secs to provide sufficient working time
• The cement should be used when the
surface is still glossy. Once the cement
becomes tacky, it no longer wets the tooth
surface www.indiandentalacademy.com

Setting Reaction
• When the powder & liquid are mixed, the
surface of powder particles is attacked by
acid releasing Zinc, magnesium & tin ions
• These ions bind to the polymer chain via
carboxyl groups
• These ions react with carboxyl groups of
adjacent poly acid chains so that cross
linked salt is formed as cement sets.

GLASS IONOMER
• It is the generic name of materials based on the
reaction of silicate glass powder & poly acrylic
acid
• Acquires name from its formulation of glass
powder & and ionomer that contains carboxylic
acids
• Available in 9 types out of which type I is used for
luting
• Particle size for luting cement is 15 micro mm

Composition
• Powder:
– Calcium fluoro alumino silicate glass
– Lanthanum, stauntium, barium or ZnO –
provide radio opacity
• Liquid:
– Aqueous soln of poly acrylic acid 45-50%
– Copolymer with itaconic, maleic or
tricarboxylic acid – increases reactivity,
decreases viscosity & decreases tendency to
gelation
– Tartaric acid – improves handling
characteristics & increases working timewww.indiandentalacademy.com

Manipulation
• P/L ratio: 1.25:1gm
• Mixing time: 45-60 secs
• Considerations for long standing retention:
– Surface of prepared tooth must be clean & dry
– Consistency of mixed cement must allow complete
coating of surface irregularities & complete seating of
prostheses
– Excess cement must be removed at appropriate time
– Protection of restoration surface must be ensured to
prevent cracking or dissolution

• P/L ratio recommended by manufacturer should be
followed
• A cool & dry glass slab or paper pad can be used
which extends working time
• Powder and liquid should be dispensed on glass
slab just before mixing, otherwise precise acid
water ratio is altered
• Powder should be incorporated into liquid rapidly
with a plastic spatula
• Mix should have a glassy appearance which
indicates unreacted poly acid on the surface. This
acid is critical in bonding with the tooth surface
• Dull surface indicates inadequate acid for bonding

Setting Reaction
• When powder & liquid are mixed to form a paste,the acid
etches the surface of glass particles & calcium, aluminum,
sodium & fluorine ions are leached into aqueous medium
• Poly acrylic acid chains are cross linked by calcium ions
that are replaced by aluminum ion within next 24hrs
• Sodium & fluorine ions don’t participate in cross linking
• The cross link phase becomes hydrated over time with the
same water used for mixing. This process is called
maturation.
• Water plays an important role here
– Acts as reaction medium
– Slowly hydrates cross linked matrixwww.indiandentalacademy.com

RESIN MODIFIED GIC
(HYBRID IONOMER)
• Here to avoid moisture sensitivity & low early
strength of GIC resulting from slow acid base
setting reaction, polymerizable functional groups
can be added to impart more rapid curing when
activated by light or chemicals
• These products are considered DUAL CURE, if
one polymerization mechanism is used
• If both the mechanisms are used, they are
considered TRI CURE cementswww.indiandentalacademy.com

Composition
• Powder:
– Ion leachable fluoro alumino silicate glass
particles
– Initiators – for light/chemical curing
• Liquid:
– Water
– Poly acrylic acid modified with methacrylate or
hydroxymethyl methacrylate (HEMA)
monomers -- responsible for polymerization

Manipulation
• P/L ratio : 1.6:1gm
• Working time: 2.5mins
• The powder is fluffed before dispensing
• Liquid is dispensed by keeping vial vertical to
mixing pad
• The powder is incorporated into the liquid within
30 secs to give a mousse like consistency
• The cement is applied to a clean, dry tooth which
is not desiccated.no coating agent is needed
• HEMA is known contact allergen, so use of
protective gloves & no touch technique is
recommended. www.indiandentalacademy.com

Setting reaction
• The initial setting reaction of material
occurs by the polymerization of
methacrylate groups
• The slow acid-base reaction will ultimately
be responsible for the unique maturing
process & final strength
• The overall water content is less to
accommodate the polymerizable ingredients

COMPOMER
• The search for a material that has fluoride
releasing capability of conventional GIC &
durability of composites has led to
introduction of poly acid modified
composite or Compomer
• Has ability to release fluoride & undergoes
acid base reaction in the presence of saliva

Composition
• Provided as 1 paste, light curable material
• Sensitive to moisture so packaged in
moisture proof pouch
• Contents:
– Silicate glass particles
– Sodium chloride
– Poly acid modified monomer without any water

• Recently, two component materials,
consisting of 2 pastes as powder & liquid
are available
• Powder:
– Strontium aluminum fluorosilicate
– Metallic oxides
– Chemically or light activated initiators
• Liquid:
– Polymerizable methacrylate/carboxylic acid
monomers
– Multi functional acrylate monomers
– Water

Manipulation
• For 1 paste system,
– Tooth structure structure should be etched before
application of dentin bonding agent & the cement
– Finishing of restoration requires same process as for
resin composites
– Cement mix is placed only on the prostheses, & the
prostheses is seated with finger pressure
– After 90secs have elapsed from the end of mixing, the
material should reach a gel state,at which time the
excess cement is removed
– The margin should be light cured immediately to
stabilize the prostheses
– The chemical cure should complete the setting reaction
in approx 3mins in oral environment
– May take 10mins or more to set in ambient airwww.indiandentalacademy.com

Setting reaction
– Setting is initiated by photo polymerization of acidic
monomer that yields a rigid material
– During the service life of the restoration,the set material
begins to absorb water in the saliva that contributes the
acid base reaction between the acidic functional groups
within the matrix & silicate glass particles
– It is this acid base reaction induced by water absorption
that eventually sustains fluoride release
– Because of absence of water in the formulation, the
cement mix is not self adhesive, so separate dentin
bonding agent is needed

– Because of presence of water, these materials
are self adhesive & an acid base reaction starts
at the time of mixing

RESIN CEMENTS
• Have become popular because of the
development of direct filling resins with
improved properties,benefit of acid etch
technique for attaching resins to enamel &
the potential to bond to dentin conditioned
with organic or inorganic acid
• These are essentially flowable composites
of low viscosity

Composition
• Chemically activated resin cements:
– Available as a powder & a liquid or 2 pastes
• Light activated resin cements
– They are single component light curable resin based
composites
• Contents
– A resin matrix with silane treated inorganic fillers
– Fillers are silica or glass particles and/or colloidal silica
used in microfilled resins
– Dentin bonding agent

Activation
• For chemically activated resin cements
– The powder & liquid are combined by mixing
on a paper pad for 20-30secs
– Removal of excess cement is difficult if it is
delayed until cement has polymerized
– Best to remove excess cement immediately
after the prostheses is seated
– Suitable for all types of prostheses
– Light transmitting prostheses thicker than
2.5mm should be bonded chemically

• For light curable resins
– Used for cementation of thin ceramic
prostheses, resin based prostheses & direct
bonding of ceramic & plastic orthodontic
brackets where the thickness of appliance is
less than 1.5mm thereby allowing adequate
transmission of light
– The time of exposure to light should never be
less than 40secs
– Excess cement should be removed as soon as
seating is completed

Bonding of resin based veneers,
inlays, onlays, crowns & FPDs
• Currently,several material systems are available to
fabricate composite based inlays, onlays, crowns
& bridges as final restorations
• So depending upon the cement of choice,the
surface for bonding can be grit-blasted to increase
roughness for bonding and/or it can be treated
designated adhesive
• This adhesive is often based on the same monomer
that is used to fabricate the prostheses
• Sufficient time must be allowed for adequate
penetration & diffusion to occur(30mins)

Bonding of ceramic prostheses
• Ceramic restorations are quite translucent, & require specific
shades of luting cements to maximize their esthetic appearance
• Resin cements are choice for all ceramic inlays, crowns &
bridges for their ability to reduce fracture & because of range
of shades available to produce optimal esthetic appearance
• The inner surfaces of ceramic prostheses with a glassy phase
usually are etched & a silane coating(Eg: Glycerin) maybe
applied to achieve retention
• To assist clinician to select proper shade of cement, systems
that provide water soluble try in materials with the same
shades as the cements are also availablewww.indiandentalacademy.com

Characteristics of abutment
prostheses interface
• When 2 relatively flat surfaces are brought into
contact,like fixed prostheses placed on a prepared
tooth,a SPACE exists between the substances on a
microscopic level
• These surfaces on microscopic level are rough i.e.,
they exhibit peak and valleys
• When 2 surfaces are placed against each other
there are only point contacts along the peaks
• The areas which are not in contacts, become open
space,influential in oral fluid flow & bacterial
invasion

• Luting agents flow and set to solid form
within mins within these spaces & not only
seal them but also improve retention of
prostheses
• If the luting cement is not fluid enough, it
can produce voids along the peaks &
valleys which can increase the tensile stress
within the crown under occlusal forces

Preparation of tooth & restoration
for cementation
• Performance of restoration is degraded if it or prepared
tooth come in contact with water, saliva or blood
• The restoration & the preparation should be clean & dried
& the tooth should be well isolated before cementing
• The tooth can be cleaned by air drying. Care should be
taken not to desiccate it completely otherwise it will
damage the odontoblasts
• In case of using non-adhesive cement like zinc phosphate,
the prepared tooth is cleaned with pumice or
chlorhexidine, dried gently & then a thin coat of varnish or
bonding agent is applied-it will decrease post operative

• The fitting surface of restoration can be best
prepared by air abrasion with 50 micro m
alumina
• Studies have shown 64% increase in
retention with air abrasion
• Care should be taken while abrading with
alumina that it should not abrade the
smooth margins of restoration
• Other alternative techniques include steam
cleaning, ultrasonics or organic solvents

Procedure for luting prostheses
• To be effective, luting agent must be
sufficiently fluid enough to flow into a
continuous film of 25-40micro mm
thickness without fragmentation
• Procedure consists of
– Placing cement on inner surface of prostheses
– Seating the prostheses on preparation
– Removing excess cement at an appropriate time

1. Placement of cement on inner surfaces of
prostheses
– Should coat entire inner surface of crown & slightly
extend over the margins of restoration to ensure that
the space between the crown& tooth is completely
sealed
– Should fill half of the interior of crown
– Occlusal aspect of tooth preparation should be free of
voids. This is to ensure that there is no air entrapment
in critical areas during initial seating
– If the void is present, any occlusal force over the
voids in ceramic inlay, onlay or crown would increase
the tensile stress & cause fracture of restoration

2. Seating of prostheses
- Use moderate pressure to displace excess cement
and to seat the crown on the prepared tooth
- After the marginal gap area is evaluated for
closure at 3 or more points with an explorer, the
patient may be asked to bite on a soft wood or a
cotton roll to ensure complete seating
- Excess cement is expelled through the space
between the margins of restoration & prepared
tooth surface
- As the prostheses reaches its final position on
prepared tooth, space for expelling excess cement
becomes smaller, making seating more difficult

To facilitate seating
- Cement of low viscosity can be used
- Taper of preparation can be increased
- Height of crown preparation can be
decreased
- By creating vibration, by tapping on
prostheses while applying pressurewww.indiandentalacademy.com

• Evaluation of complete seating of
prostheses
– This can be ensured by 2 means
1. Evaluation of occlusion
2. Evaluation of the margins at a minimum 3
points before cement is set

3. Removal of excess cement
- Excess cement accumulates around the margin of
restoration after completion seating
- Its removal depends upon properties of cement used
- If the cement sets to brittle state & not adhering to
surrounding structures,it is best to remove after it sets
- Zinc phosphate & ZoE cements should completely set
before removal.They should be allowed to set for about
2.5mins
- In case of GI, zinc poly carboxylate or resin cements,
which have the ability to adhere both chemically &
physically, a separating media eg:petroleum jelly can be
coated on surrounding surfaces, thereby inhibiting

• Care should be taken to avoid contact of
separating medium at the margin of
restoration & tooth
• The rationale is,in case of these cements,
they become viscous but not rigid which
facilitates removal
• In case of dual cure resins, light irradiation
for 10secs is recommended

POST CEMENTATION
PROCEDURES
• Aqueous cements (zinc phosphate, ZOE) continue
to mature even after defined setting
• If they are allowed to mature in an isolated
environment i.e., free of contamination with oral
fluids & loss of water by evaporation, the cements
will acquire additional strength & become more
resistant to dissolution
• As a precaution, the prosthodontist must apply a
varnish coat or a bonding agent along the margin
of cemented restoration before discharging patient

MECHANISM OF RETENTION
• Prostheses can be retained by MECHANICAL or
CHEMICAL means or by combination of both
• On microscopic level, the interfacial surfaces are
rough & the cement fills the irregular crevices
along both surfaces
• The cement tooth & cement prostheses interfacial
regions then exhibit a sealed continuum which is
void free
• It can resist shear stress acting along the interface.
This is mechanical retention

• To ensure complete retention & wetting of
surfaces, chemical bonding is ideal
• It resists interfacial separation & increase retention
• Aqueous cements (GIC, etc) provide chemical
bonding through chelation of acrylic acids to both
organic & inorganic components of tooth
• Resin cements are believed to bond to calcium in
dentin
• Contemporary dentin bonding agents which are
hydrophilic & can penetrate into the porosities in
dentin created by acid etching exhibit high bond
strength thru micro mechanical retention

DISLODGEMENT OF
PROSTHESES
• Fixed prostheses can de-bond because of 2
factors
1. Biological factors
- Secondary caries
In oral environment, luting agents are
immersed in aqueous solutions. In this situation, the
cement near the margin can dissolve & erode, leaving
a space
This space can be susceptible to fluid inflow,
plaque accumulation & secondary caries

• Physical factors
1. Intraoral forces
2. Flaws within crown surface
3. Porosities within cement
This is particularly evident in brittle
prostheses like glass ceramic crown
• Modes of failure associated with cement:
1. Fracture of cement
2. Leakage along the interface

• Factors influencing retention of fixed
prostheses
1. Film thickness
Should be 25-40micro mm
Thinner film has fewer internal flaws and has
less chances of fracture
2. Strength
Should have high strength
Research has shown that the cements which
have high compressive, shear or tensile
strength require higher forces to dislodge
prostheses than cements with lower strengths

3. Dimensional changes
Should be minimized during seating
These are mostly because of
-Loss or gain of water
-Differences in co-efficient of
thermal expansion of cement
prepared tooth & prostheses.
So, it is important to isolate the cement
immediately after removal of excess
4. Cements with chemical bonding to both tooth &
prostheses surfaces
They reduce the separation at the interface &
maximize inherent property of strength on
retention

COMPARITIVE STUDIES

SUMMARY
• Dental luting agents form the link between fixed
restoration & supporting tooth structure
• These luting agents along with their physical,
chemical, biological & esthetic properties increase
the performance of restoration
• It appears a single adhesive will not suffice in
modern day practice
• To date no adhesive can completely compensate
for the shortcomings of preparation, retention &
resistance forms or ill fitting, low strength
restorations
• Practitioners must be aware of the virtues and
shortcomings of each cement & select them
appropriately. www.indiandentalacademy.com

REFERENCES
• PHILLIP’S
SCIENCE OF DENTAL MATERIALS - 11TH
edition
• ROSENSTIEL, LAND & FUJIMOTO
CONTEMPORARY FIXED PROSTHODONTICS – 3RD
edition
• CRAIG, O’BRIEN, POWERS
DENTAL MATERIALS- 6TH
edition
• ROSENSTIEL, LAND & CRISPINE.
DENTAL LUTING AGENTS:A REVIEW OF CURRENT
LITERATURE. J PROSTHET DENT 1998;VOL 80:280-
301.
• DIAZ –ARNOLD, VARGAS & HASERTON .
CURRENT STATUS OF LUTING AGENTS FOR FIXED
PROSTHODONTICS 1999;VOL 81:135- 141.

THANK YOU

Luting cements/ dental courses/endodontic courses

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