Dental cements and cementation procedures

Dental cements & cementation
procedures
Charles J. Goodacre, DDS, MSD
Professor of Restorative Dentistry
Loma Linda University School of Dentistry
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Provisional Cements
•  They are typically zinc oxide powder or zinc oxide paste
mixed with eugenol liquid
•  Noneugenol formulations are available that do not soften
resin (as in provisional crown). They use carboxylic acids in
place of eugenol
•  The liquid can be ethoxybenzoic acid, known as ZOEBA,
making it stronger
•  TempBond Clear is a translucent cement with Triclosan (an
antibacterial & antifungal agent)

The Hardening of Dental
Cements & Constituents
•  There are 2 hardening mechanisms of dental
cements
1) Acid-base reactions
2) Polymerization reactions
•  Acid-Base Reaction cements use one of three
powders & one of three liquids
•  Polymerization Reaction cements use a composite
resin (resin matrix with filler particles) that is
polymerized by light, chemicals, or a combination of
both (dual)

Zinc Phosphate Cement
•  Powder
90% zinc oxide
10% magnesium oxide
•  Liquid
2/3rds Phosphoric acid
1/3rd Water & aluminum phosphate
(water is critical as it controls rate of
reaction)
•  Hardened cement is undissolved
powder particles in matrix of zinc
aluminophosphate compound

Characteristics of Zinc
Phosphate Cement
•  Higher solubility than other cements except for
Polycarboxylate that has a comparable solubility
•  Good marginal fit minimizes the
exposure of the cement to oral fluids
and has negated this potential
disadvantage for decades

Phosphate Cement
•  Postcementation sensitivity can occur
•  Acid penetration of dentin tubules
causes short – term sensitivity for
some patients

Phosphate Cement
•  No fluoride release
•  For patients with high caries
potential, the cement does not
help protect the tooth from caries

Phosphate Cement
•  No adhesion
•  Retention provided mechanically

Phosphate Cement
•  No adhesion
•  Incremental, slow mixing required
•  Reaction heat needs dissipation

Zinc Phosphate Mixing
•  Dispense powder
& 5-6 drops of
liquid
•  Incremental
mixing for 15-20
seconds per
increment
•  1.5 – 2 minutes
total mixing time

Advantages of Zinc
Phosphate
•  Longest record of very effective and
successful use
•  Zinc phosphate cement appears to
be the least technique sensitive
cement and has been successfully
used by thousands of clinicians with
varying degrees of meticulousness
for decades
Anusavice, 1989

Advantages of Zinc
Phosphate
•  Longest record of very effective and
successful use
•  Increased working time may be beneficial
when cementing multiple single units or a
long – span fixed prosthesis with multiple
retainers

Polycarboxylate Cement
•  Powder (like zinc phosphate)
Zinc oxide & Mg or Sn oxide
Stannous fluoride to ↑ strength
and improve handling - not a
source of fluoride release
•  Liquid
Polyacrylic acid or copolymer of acrylic acid
(carboxylic, itaconic). Some brands have the
acid freeze dried and placed in powder with
liquid being water
•  Hardened cement is undissolved powder
particles in an amorphous gel matrix

Characteristics of
•  Biocompatability (kind to pulp)
•  Good for use with sensitive teeth
•  Good for base

Characteristics of
•  Adhesion

Characteristics of
•  Adhesion
•  Retention to tooth structure and
decreased microleakage
•  Good for blocking out undercuts

Characteristics of
•  Adhesion
•  Short mixing time (30 seconds)

Characteristics of
•  Adhesion
•  Mix quickly to obtain adhesion

Characteristics of
•  Adhesion
•  Short working time
(1.75 – 2.5 minutes)

Characteristics of
•  Adhesion
•  Short working time
(1.75 – 2.5 minutes)
•  Apply rapidly to crown and seat
•  Not well suited for cementing
several crowns at one time

Polycarboxylate Mixing
•  Dispense
measured amount
of powder & liquid
•  Bulk mixing by
incorporating all
powder into
liquid at one time
•  30 seconds maximum mixing time
•  Mixing too thick and loss of gloss
prevents adhesion and complete seating

Polycarboxylate Adhesion
•  There is chemical adhesion to the tooth by
the polyacrylic acid liquid reacting with the
calcium of the hard tooth structure. May also
produce a weaker bond to the collagen of the
dentin
Smith, 1968

•  To achieve adhesion, the cement should be
mixed rapidly (30 seconds maximum) and the
restoration seated before the cement loses it
surface gloss (so some polyacrylic acid liquid
is still available for interaction with the tooth
when the cement comes into contact with the
tooth)
Phillips, 1991

•  To insure interaction between the tooth and cement,
the tooth surface should be cleaned to remove the
smear layer using a 20% polyacrylic acid solution
(GC Cavity Conditioner or Ketac Conditioner) for 10
seconds followed by water rinsing
Smear Layer

Polycarboxylate Adhesion To
Crown Can Be A Problem
•  There were early failures where the crown
came loose from the cement
•  The metal surface must be clean to achieve a
bond with carboxylate cement
•  Airborne particle abrasion is the preferred
method for achieving a clean surface that will
interact with the cement
Ady and Fairhurst, 1973

Glass Ionomer Cement
•  Powder (Ca, Fl, Al, SiO2)
Calcium fluoroaluminosilicate glass
•  Liquid
Originally polyacrylic acid but now most use
copolymer of acrylic acid (itaconic, maleic,
or tricarboxylic). Some brands have the
acid freeze dried and placed in the
powder with the liquid being water
•  Hardened cement composed of
undissolved powder in polysilicate gel
matrix of Ca & Al salts

Characteristics of Glass
Ionomer Cement
•  Fluoride release

Ionomer Cement
•  Good for patients with a history of
caries experience
•  Good for prepared teeth with dark but
hard dentin areas (previously
decalcified areas)

Ionomer Cement
•  Adhesion

Ionomer Cement
•  Adhesion
•  Somewhat short mixing time (45
seconds maximum when mixed by
hand)

Ionomer Cement
•  Adhesion
hand)
•  Apply to crown and seat fairly rapidly

Ionomer Cement
•  Adhesion
hand)
•  Early moisture sensitivity

Ionomer Cement
•  Adhesion
hand)
•  Protect margins with resin glaze

Ionomer Cement
•  Adhesion
hand)
•  Long time to reach full
strength (several days)

Ionomer Cement
•  Adhesion
hand)
•  Long time to reach full
strength (several days)
•  No vigorous chewing right away

Glass Ionomer Adhesion
•  There is chemical adhesion to the
tooth by the polyacrylic acid liquid
reacting with the calcium in the
apatite. Mechanism comparable to
polycarboxylate cement
•  A 20% polyacrylic acid liquid should
be used to condition the tooth surface
(remove smear like) like
polycarboxylate

Glass Ionomer Mixing
•  Measured amount of
powder to specified
number of drops
of liquid
•  Bulk mixing in
2 increments
(20 seconds total mixing)
•  Maximum mixing time of
45-60 seconds

Fluoride Release & Caries
•  GI releases fluoride
•  There is Fl update in the underlying
dentin
•  Fl release influences Fl concentration of
adjacent teeth
•  Adjacent carious lesions were
significantly reduced

Resin-Modified Glass
Ionomer Cement
•  Powder (Ca, Fl, Al, SiO2)
Calcium fluoro-alumino-silicate glass and
initiators for light and chemical
polymerization
•  Liquid (solution of hydrophilic
monomers)
Polyacrylic acid and a hydrophilic
(water soluble) monomer such as HEMA
(hydroxyethyl methacrylate)
•  Light-activated resin polymerization
precedes formation of the polysilicate
gel matrix

Characteristics of Resin
Modified Glass Ionomer
•  Good for patients with a history of
caries experience
•  Good for prepared teeth with dark but
hard dentin areas (previously
decalcified areas)

•  Adhesion

•  Adhesion
•  Somewhat thick when mixed

•  Adhesion
•  Not well suited for cementing
several crowns at one time or a
long span multi – abutment fixed
prosthesis

•  Adhesion
•  Reduced early moisture sensitivity

•  Adhesion
•  Marginal cement not as
susceptible to early dissolution
because of resin content. No
need to coat margins

•  Adhesion
•  Good early strength

•  Adhesion
•  Resin present in cement enhances
early strength and resistance to
early dislodgment. Excess should
be removed before it is completely
hardened. Hardened excess
requires scaler to remove.

•  Adhesion
•  Expands upon setting

•  Original problem with all –
ceramic crown fracture and
posts fracturing teeth seems to
be resolved by lower expansion

Resin Modified Glass Ionomer Mixing

Resin Cement
•  Similar to composite resins (most use a resin matrix
of bis-GMA; UDMA; and TEGDMA with silane-
treated inorganic fillers (silica, glass, or colloidal
silica)
•  Most resin cements require an adhesive monomer
(dentin bonding agent) such as HEMA, 4-META,
and MDP. HEMA & MDP are present in the dentin
bonding agent & the resin cement. 4-META does
not require a separate bonding agent

Resin Cement
•  Resin cements can be polymerized chemically, by light,
or by using a dual polymerization process

Resin Cement
•  With chemical polymerization, 2 pastes are mixed
together that contain BP initiator (benzoyl peroxide) &
amine activator (N-dimethyl-p-toluidine). Amine reacts
with BP to form free radicals & initiate polymerization

Resin Cement
•  With chemical polymerization, 2 pastes are mixed
together that contain BP initiator (benzoyl peroxide) &
amine activator (N-dimethyl-p-toluidine). Amine reacts
with BP to form free radicals & initiate polymerization
•  Light polymerization uses a single paste system. Light
causes the photosensitizer CQ (camphorquinone) to
interact with the amine DMAEMA (dimethylaminoethyl
methacrylate) to form free radicals & initiate
polymerization

Cements
•  Not soluble
•  Adhesion (micromechanical)
•  Multiple colors available
•  Extended working time for light
polymerized and dual polymerized
•  Increased retention?
•  Increased all – ceramic crown strength
•  Fluid / moisture control is critical
•  Requires meticulous attention to protocol
to achieve bonding

Calcium Aluminate Cement
•  Powder
Calcium aluminate &
some glass ionomer
components added
to improve handling
(GI components are
not identifed)
•  Liquid
Water

Characteristics of
Calcium Aluminate Cement
•  Nano crystals (hydroxyapatite) form on the
surface of the tooth & crown that seal the
interface
•  Bonds to the tooth using the same principle as
remineralization
•  Fluoride released initially
•  No hydraulic pressure resistance
•  Does not produce pulpal inflammation

Calcium Aluminate Mixing
•  Place capsule in activator
and press handle down for
3 seconds
Applicator
Activator

3 seconds
•  Mix 8-10 seconds at
4 to 5,000 rpm
Applicator
Activator

•  Insert mixed capsule into
applicator and express
mixed cement into crown

3 seconds
•  Mix 8-10 seconds at
4 to 5,000 rpm
•  Insert mixed capsule into
applicator and express
mixed cement into crown
•  Stabilize for 2 minutes until
rubbery, then remove excess, let
set an additional 4 minutes

Removal of Provisional Crown
•  Spoon excavator placed carefully under
margin of provisional restoration so as not to
damage finish line on tooth (careFUL,
careFUL, careFUL)
•  Use a spoon excavator to engage axial resin
occlusal to the margin
•  Hemostats used carefully so as not to exert
excess lateral leverage on teeth

Provisional Cement Removal &
Preparing The Tooth Surface for
Definitive Cementation
•  Clean the tooth mechanically or chemically
•  Mechanical cleaning using hand instruments,
cotton pellets, disposable applicators, pumice
•  Chemical cleaning using saliva, acids, or
special agents such as degreasers, dentin
desensitizers, antimicrobials

•  Polyacrylic acid liquid (20% PAA) is used with
Polycarboxylate and GI cements (10 second
application) to remove the smear layer without
opening the dentinal tubules
•  Phosphoric acid is used to etch the tooth
surface in preparation for use of a resin cement
(other than self-etching cements)
Provisional Cement Removal &
Preparing The Tooth Surface for
Definitive Cementation (con’t)

Clinical Trial Placement &
Adjustment
•  All residual provisional cement must be
removed (requires drying & examining)

Adjustment
•  Adjust proximal contacts
first (which one is heavy?)

Adjustment
•  Adjust proximal contacts
first (which one is heavy?)
•  Occlusal adjustments are made after
proximal contacts are correct and the
crown is fully seated

Which Proximal Contact is Heavy?
•  Proximal contact resistance to floss

•  Burnishing of metal or articulating film
(mylar) / ribbon for contact location

•  Shim stock is most accurate for presence
or absence of contact

•  Patient’s perception of pressure in front of
or behind crown

•  Patient’s perception of pressure in front of
or behind crown
•  Marginal fit on mesial versus distal

Marginal Finishing
•  Improves smoothness and transition
zone of good fitting crowns / inlays
Courtesy of
Richard Tucker & Frederick Westgate

Marginal Finishing
•  It doesn’t enhance crowns that
“fit like socks on a rooster”
Courtesy of
Richard Tucker & Frederick Westgate

Marginal Finishing
•  Fine grit rotary instruments and
abrasive discs / rubber points

Marginal Finishing
•  Fine grit rotary instruments and
abrasive discs / rubber points
•  Can be accomplished both before
and after cementation

Marginal Finishing
•  Soflex discs
•  Green stone / white stone shaped as needed
or fine grit diamonds rotated slowly from
crown to tooth
•  Pumice

Marginal Finishing
Learn to Use Light
Reflections Across
the Margin

Marginal Finishing
Tooth extending
beyond crown
Crown extending
beyond tooth
Learn to Use Light
Reflections Across
the Margin

Occlusal Adjustment
•  With multiple crowns,
it is best to adjust
them one at a time,
making sure the
occlusion on other
teeth is the same
after each crown is
adjusted as it was
before the crown was
placed

Achieving Complete
Seating During Cementation
•  Finger pressure (use with anterior crowns, all
– ceramic crowns, and posts and cores)

Achieving Complete
•  Finger pressure (use with anterior crowns, all
– ceramic crowns, and posts and cores)
•  Use patient’s musculature by having them
bite on a wooden stick or peg

Achieving Complete Seating
A horizontal and vertical rocking motion of the loaded
wooden stick for 30 seconds decreased the vertical
seating discrepancy by a mean of 203 micrometers
Rosenstiel, J Am Dent Assoc 1988;117:845-848

Achieving Complete Seating
•  Use a rocking motion or 360
degree rotation of wooden
stick after crown appears to be
fully seated
A horizontal and vertical rocking motion of the loaded
wooden stick for 30 seconds decreased the vertical
seating discrepancy by a mean of 203 micrometers
Rosenstiel, J Am Dent Assoc 1988;117:845-848

Verifying Complete
•  Marginal fit through cement

Verifying Complete
•  Marginal fit through cement
•  When margin is visible, wipe away excess
and see if additional pressure expresses
more cement

Isolation During
Setting of the Cement
Isolation with cotton rolls

GI Cement Protection
While Setting
•  Glass Ionomer should be coated with
a “resin bonding agent” or “resin
glaze” while it is hardening
•  Apply the coating over the marginal
excess and light polymerize it
•  Recoat the margins with resin after
the cement has hardened and the
marginal excess has been removed

Stabilization During Setting
FINGER PRESSURE
HAVE PATIENT BITE
ON COTTON ROLLS

Cement Removal
•  Explorer & Floss (effective for hardened brittle
cements like zinc phosphate)

Cement Removal
•  Explorer & Floss can also be used with partially
polymerized Resin / Resin Modified Glass
Ionomer cements. Use brief light exposure (2
seconds), remove excess, then completely
polymerize

Cement Removal
•  Explorer & Floss can also be used with partially
polymerized Resin / Resin Modified Glass
Ionomer cements. Use brief light exposure (2
seconds), remove excess, then completely
polymerize
•  Scaler (required for hardened Glass Ionomer,
Resin – Modified GI, and Resin
that has set completely

Cementation of Crowns
on Dental Implants
•  Many, if not most, of the crowns that attach to dental
implants are being cemented rather than being screw
retained
•  This process can produce substantial complications

Fistulas Associated
With Dental Implants
•  117 of 11,764 implants affected
•  Mean of 1%
•  Initially, they were
associated with loose
abutment screws but
new causes have
emerged
1%

With many implant crowns being cemented,
we are now seeing fistulas and adverse
responses from retained cement
Cementation of Crowns
on Dental Implants

Excess Marginal Cement
Is An Emerging Problem
•  A documented cause of peri-implant
disease Pauletto, 1999; Gapski, 2008
•  If the excess can be removed, the
problem is resolved for most patients
•  It can take several years before the
excess cement causes disease
Thomas, J Periodontol 2009;80:1388-92
6-30-2011

Peri-Implant Disease
•  “If peri-implant disease in the form of
peri-mucositis or peri-implantitis is seen
to develop around the tissues of a
cement retained implant restoration
then excess cement must be
considered as a potential etiologic
factor Wadhwani, 2011
6-30-2011

Examples of Adverse Soft
Tissue Responses to
Retained Cement Caught
Early and Corrected but it
Produced Pain and Required
Professional Treatment

Example 2
Courtesy of Dr. Joseph Kan

4 months postcementation,
surgical exposure of inflammatory site
Example 3
Courtesy of Dr. Chandur Wadhwani

Bone Loss Requiring
Surgery & Bone Grafting to
Save Implant

Implant placement:
2/14/07
Restored: 8/5/08
5/20/09
Example 1

Example 2

Implant Loss from
Retained Cement

Example 1

RESIN CEMENT
L L
Example 2
Courtesy of Dr. John Agar

This Patient
is a DENTIST !
Courtesy of Dr. Franco Audia
Example 4

A Second Problem With
Cemented Implant Crowns Is
Incomplete Seating
•  Abutment height is greater than most tooth
preparations
•  Parallelism of abutments is often greater than
prepared teeth
•  Adaptation of crown may be better
•  Viscosity of cement prevents extrusion of all
the excess

Some Cements Are Nearly
Impossible To Completely
Remove From Abutment
And Implant Surfaces

6 experienced clinicians
Zinc phosphate, GI, Resin
1.5 – 3.0 mm subgingival
Courtesy of Dr. John Agar

Type of Cement
and
Amount Retained

Instrument and
Amount of
Retained Resin
Cement (Panavia)

Radiographic Density
of Cements
•  Measured potential to be detected on
radiographs if cement is left behind (tested 1 and
2 mm thicknesses)
•  Only Zn containing cements (TempBond &
Fleck’s ZnPO4) were detected at 1 mm
•  GI (RelyX Luting), Resin (RelyX Unicem), and
Improv cements were only detected when
thickness was > 2 mm
Wadhwani, J Prosthet Dent 2010;103:295-302

Cementation Guidelines
•  Abutment should have texture
(not be highly polished)

Cementation Recommendations
•  Use a provisional cement (ZOE) such as temp-
bond unless the retention is compromised by a
short abutment, a very tapered abutment, or the
screw access hole eliminates retentive surface(s)

When retention is compromised,
use zinc phosphate cement

•  Loosened after 2
months with ZOE

Minimizing Cement Extrusion
When Cementing Crowns
•  Express poly (vinyl siloxane) impression material
inside the crown to make a PVS die
•  Mix cement and place it inside the crown, seat the
crown on the PVS die to express the excess
cement
•  Quickly remove crown from PVS die and seat in
the mouth
Wadhwani, J Prosthet Dent 2009;102:57-58
Caudry, J Prosthet Dent 2009;102:130-131

Thank You For Your Attention
Charles J. Goodacre, DDS, MSD
Professor of Restorative Dentistry
Loma Linda University School of Dentistry

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