Dental Cements by Silas M. Toka

Dental Cements
Silas M. Toka
BDS III, 2010 (UoN)
8th October, 2010

Introduction
Def: A dental cement is a biomaterial
composed of but not limited to an acid
and a basic component that react to set
into a rigid material.
 Dental cements may also be polymeric
i.e. set through polymerization reactions.

Applications of Dental Cements
 Dental Cements have both temporary and
permanent applications:
i. Luting
ii. Lining
iii. Cementing Orthodontic appliances
iv. Fissure sealants
v. Root filling materials
vi. Temporary fillings
vii. Permanent fillings
viii. Core build-up

Dental Cements
1. Silicate Cements
2. Zinc phosphate Cement
3. Zinc polycarboxylate Cement
4. Glass Ionomer Cement
5. Zinc oxide Eugenol Cements
6. Calcium hydroxide Cement
7. Resin Cements
8. Mineral Trioxide Aggregate

Poly
acrylic acid
(aq.)
Phosphoric
acid (aq.)
Zinc
Oxide
Alumino-
silicate
glass
Glass
Ionomer
Cements
Zinc
Polycarboxylate
. cements
Zinc
phosphate
cements
Silicate cements
Dental Cements as acid + base formulations.
Eugenol
Zinc
Oxide
Eugenol

1. Silicate Cements
 Based on fluoroaluminosilicate glass
and aq. phosphoric acid.
 Also called silicophosphate cements.
 First tooth colored filling material
(1870).
 Not in use today.

Drawbacks of Silicate Cements
 Acidic (Phosphoric acid)
 Soluble in the mouth
 Low wear resistance
 Staining at the margins
 Short lasting fillings
The fluoroaluminosilicate glass of Silicate
cements formed the basis for the modern
day Glass ionomer cements.

2. Zinc phosphate Cements
 One of the oldest cements (the oldest
luting cement).
 Powder: 90% ZnO, 10% MgO.
 MgO serves to whiten the powder.
 Small quantities of oxides and fluorides.
 SiO2 1.4% - Calcination aid.
 BiO3 0.1% - Smoothens powder.

Zinc phosphate Cements (cont’d)
 Liquid: 60-70% aq. Phosphoric acid.
 Zn or Aluminium phosphate (achieved by
dissolving Zn 7.1% or Al 2.5% in the
liquid).
 They buffer the liquid thus partially
neutralizing/reducing the reactivity of the
P & L.
 The water in the acid controls the
ionization thereby affecting P/L
(acid/base) rxn.

Note on the liquid:
 Not to be dispensed on the slab until
mixing is to be initiated because water will
be lost to air by evaporation.
 Bottle should thus also be carefully
stoppered;Evaporation lowers pH of the
Phosphoric acid:- Issues with biocomp’t.
- Ions needed for rxn.
 Cloudy liquid is totally acidic and should
be discarded.
 Loss or gain of water in H3PO4 both
compresssive&tensile strength of cement.

Manipulation
 P:L ratio dependent on clinical application.
 A high P:L ratio gives a stronger set
material(so use max. powder possible
even when thin mix such as for luting is
needed).
 Thinner mix – Low viscosity(used in
luting; more soluble& weaker
mechanically).
 Mix on a cold glass slab 1 – 1.5 mins.
 Small increments added.

 Brisk spatulation;mix over wide area,each
increment for 15-20 sec before adding.
 Complete mixing in 1.5 – 2mins.
 For luting, low viscosity mandatory.
 Seat prosthesis immediately before matrix
formation occurs and hold it under
pressure until cement sets.
 Keep field of operation dry.
 Remove excessive cement after set.
 Apply varnish or non-permeable coat on
edges to give time to mature and develop
resistance to dissolution in oral fluid.

Setting Reaction
ZnO+2H3PO4 Zn(H2PO4)2+H20
ZnO+Zn(H2PO4)4+2H2O Crystalline
[Hopoeit]
 Unreacted core of ZnO remains.
Set Cement
Matrix of Zinc
aluminophosphate
Rxn is exothermic;Cement sets in 5-9mins.
ZnO

Factors Affecting Setting Rxn
 Higher P:L ratio.
 Increase in temp.
 Moisture.
 Faster rate of adding powder increments
to the liquid.
 Finer particles increase rate of rxn.
 Too acidic liquids slow down setting rxn.

Biological Properties
 Freshly mixed cement has a pH of btwn
1.6-3.6;pH of 5.5 at 24hrs.
 Cement should only be placed on fresh
dentine with a subliner e.g. varnish,
Ca(OH)2, or ZnOE.
 Is a good thermal insulator – can be used
to protect pulp.
 Radio-opaque.

Mechanical Properties
 No chemical adhesion; bonding by
mechanical interlocking at interfaces.
 Compressive strength of 104MPa for
luting cements,but a diametral tensile
strength of only 5.5MPa.
 Modulus of Elasticity=13.5GPa, therefore
quite stiff and resistant to deformation
even when used as a luting cement in
high masticatory stress areas.
 Recommended P:L ratio=
 1.4g powder:0.5mL liquid.

Applications
1. Permanent luting(of crowns&bridges).
2. Lining, but only with a subliner.
3. Temporary filling, with a protective layer.
Advantages
i. Cement better than ZnOE;TF would last
longer.
ii. Good thermal insulator.
iii. Cheaper cf other luting materials.
(Resin cement kit about KSh.18,000)

Brand names
 Tenet
 Havard
 De Trey’s Zinc

3. Zinc polycarboxylate Cements
 Synonym: Zinc polyacrelate Cements.
 First chemically adhesive dental material
to be developed.
 Presented in P:L formulation.
 May be capsulated.
 Anhydrous,where the liquid is freeze
dried and incorporated in the powder.
Brand Names
Durelon
Carboco

 Powder:
(Similar to ZnPO4 Cement; Both in
composition & in manufacturing):
 90% ZnO, 10% MgO.
 MgO serves to whiten the powder.
 Stannic oxide may be substite MgO.
 Small quantities of oxides and fluorides.
 SiO2 1.4% - Calcination aid.
 BiO3 0.1% - Smoothens powder.

 One preparation contains alumina in 43%
of the powder.
 Stannous fluoride in small quantities.
Note on Stannous Fluoride
Modifies setting time.
Enhances manipulative properties.
Increases strength.
However fluoride release is only 10–15 %
that released by GIC’s.

Liquid
 Aq. Soln. of Polyacrylic acid, or
 A copolymer of polyacrylic acid with other
carboxylic acids such as itaconic acid.
 Mol. wt. of the polyacids is in the 30,000
– 50,000 range(Viscous acids).
 Hence the freeze dried formulation.
 Acid concentration varies from 32-42% by
weight.
In the freeze dried preparation, the liquid
is water.

Manipulation
 P:L = 3:1 by volume.
 With the non freeze-dried preparation, the
P:L varies from different brands;range of
1 – 5 parts of powder:1part liquid by wt.
 Mixing done on a cold glass slab;advantage
over paperpads since it can be cooled&does
not absorb liquid.
 Do not dispense the liquid until it is time for
the mix to be made.
Cool glass slab,but by no means refrigerate
the liqud!!

 Powder incorporated into the liquid in
large quantities.
 Viscosity increases steadily.
 Apply to dry tooth before cement loses
gloss in order to achieve good bonding.
 Gloss indicates presence of free carboxylic
groups on the surface of the mixture that
are vital for bonding to the calcium in the
tooth surface.
 When the viscosity is changing,and lifted
cement forms a streak (“cob web”),
discard the material.

Setting Reaction
 Particle surface dissolution by the acid to
release Zn, Mg and Sn ions,which bind to the
polymer chains via carboxyl groups.
 These ions react with carboxyl groups of
adjacent polyacid chains, so that a
crosslinked salt is formed as the cement sets.
 The hardened cement consists of an
amorphous gel matrix in which unreacted
particles are dispersed.
 The microstructure resembles that of zinc
phosphate in apperance.

Binding to Tooth Structure
 Polyacrylic acid is believed to react with
Ca2+ ions via carboxyl groups on the
surface of enamel or dentine.
 Thus the bond strength to enamel is
greater than that to dentine.
Film Thickness
 The material is pseudoplastic and
undergoes thinning at an increased shear
rate.
 Spatulation can produce a film thickness
of 25µm or less.

Biological Considerations
 Produce minimal irritation to the pulp; the
liquid’s acidity is rapidly neutralized by the
powder.
 Biocompartibility with pulp compares well
with Zinc oxide Eugenol Cements.
 It is postulated that the Polyacrylic acid
molecule is larger in size than the
Phosphoric acid of Zinc phospahate
cements.
 This limits diffusion through dentine
tubules.

Working Time
 Much shorter than for zinc phosphate
cements i.e. 2.5min cf 5min for ZnPO4.
 Lowering the temperature of the glass
slab can increase the working time, but
can also cause the polyacid to thicken
hence making the mixing difficult.
 It is suggested that only the powder be
refrigerated before mixing.
 The rationale for this is that the reaction
occurs on the surface and the cool temp.
retards it without thickening the PAA.

Setting Time
 6-9 mins (Acceptable for a luting cement).
Mechanical Properties
 Compressive strength: 55-67MPa [inferior
to ZnPO4 (104MPa)].
 Modulus of elasticity 2.4-2.4 GPa(half that
of ZnPO4 = 13.5GPa), therefore is not as
stiff, and also not as brittle.
 Has a plastic deformation potential and so
difficult to remove excess after set.

 Avoid removing cement during the
rubbery stage when luting a prosthesis as
there is a danger of the cement pulling
out from under the prosthesis leaving a
void.
 Can either start removing the cement
immediately after placing the prothesis, or
wait until set.
 Coat the outer surface of the prosthesis
with a separating medium to avoid excess
cement adhering to the surface.

Solubility
 Low solubility in water.
 Increased solubility in organic acid of pH
less than 4.5. (e.g in poor OH patients).
 Reduction of P:L ratio also increases
solubility hence increased disintegration in
the oral cavity.
Applications
 Luting (currently overtaken by GIC’s).
 Lining.
 Temporary fillings.

4. Glass Ionomer Cements
 Materials based on the reaction between
silicate glass powder and polyacrylic acid.
 Developed in 1971 by Wilson and Kent and
has properties that supersede those of
Zinc polycarboxylate and Silicate cements.
 Are an aesthetic tooth colored material
with the 3 salient properties of:
 Biocompartibility,
 Chemical adhesion to the tooth, and
 Fluoride release and re-release.

GIC’s and Related Materials
1. Conventional GIC’s/Traditional GIC’s.
2. Resin Modified GIC’s.
3. Metal Modified GIC’s.
4. Phosphonate Modified GIC’s.
5. Advanced/Highly Viscous/Condensable
GIC’s/A.R.T. materials.
6. Giomers.
7. Compomers.

GIC’s in Endodontics
Ketac-Endo
 Endodontic sealer cement based on GIC
chemistry.
 Disadvantage is that GIC is hard to
remove, making retreatment almost
impossible.
 May be used without Gutta percha cones.
 Currently, chloroform, hand instruments
and ultrasonics are used in an attempt at
removal.

Fissure Sealant Application of GIC’s
 Traditional GIC’s are viscous which
prevents penetration to depth of fissures.
 Less viscous
formulations of
GIC’s are now
available for
fissure sealant
therapy.

5. Zinc oxide Eugenol Cements
 Zinc oxide is the major component of the
cement.
 Presented as Zinc oxide powder and
Eugenol liquid, or sometimes as 2 pastes.
 The higher the P:L ratio, the faster the
material sets.
 Powder particle size affects strength; the
smaller the size, the stronger the set.
 Compressive strength ranges from 3-55
MPa depending on ZOE formulation.

Manipulation
 Mixing done on glass slab or oil-
impervious paper-pad.
 Cooling a glass slab slows down the
reaction until dew point; water
incorporated after dew point hastens the
reaction.
 Mix in increments until desired
consistency is attained.
 P:L Ratio = 5.5:1 for TF or Lining.
 P:L Ratio = 4:1 for luting.

Manipulation (cont’d)
Mixing time: 60 seconds.
Working time: 3 minutes.
Setting time: 3.5 – 4.5 minutes.
 The pH is approx. 7 at the time of
placement, which makes ZOE the least
irritating of all dental materials.
 A TF lasts approximately 3 months (Zinc
phosphate performs better).

Setting Reaction
 Consists of Zinc oxide hydrolysis and a
subsequent reaction between Zinc
hydroxide and Eugenol to form a chelate.
 Water is needed to initiate the reaction
and is also a by-product, hence the rxn
proceed faster in humid environments.
Zinc oxide + Eugenol Zinc Eugenolate

Characteristics of ZOE Cements
 Soluble in oral fluids and so if left for a
long time, the filling crumbles and
desintergrates.
 Has a palliative/soothing/optudent effect
to the pulp (manages hypersensitivity).
However, effect only when placed on
dentine; should never be placed on the
pulp – causes necrosis.
 Potential allergen to some patients.
 Irritation to soft tissue (therefore, handle
with gloves)

Characteristics of ZOE Cements
(cont’d)
 Plasticizes and interferes with
polymerization reaction of tooth colored
filling materials.
Therefore contraindicated in lining under
resin composites and compomers.
 Have a characteristic smell (of Eugenol)
and clinics will smell of it if not thoroughly
cleaned.

Formulation Modifications
 Plain unmodified ZOE will set very slowly;
Therefore, modifications:
Zinc acetate dihydrate is much more
soluble than Zn(OH)2 and will supply zinc
ions more rapidly.
Acetic acid catalyses the reaction faster
than water does because it increases the
formation rate of Zn(OH)2.

Applications of ZOE Cements
 4 types (ANSI/ADA Specification No.30):
1) Type I: For temporary cementation e.g of
provisional acrylic crown or bridge.
2) Type II: For long-term cementation of
fixed prosthesis (not so desirable cf GIC).

3) Type III: For temporary fillings (lasts a
few wks), and thermal insulating bases.

4) Type IV: For intermediate restorations
(can last up to 1 year).

5) Variety of ZOE cements also serve as
root canal sealers, and
6) Periodontal dressings.

7. Zinc oxide Eugenol Sealer Cements
 Presented as powder+ liquid.
i. Grossman’s sealer Composition
Powder/ pellet
 Zinc oxide – 42%
 Staybellite resin – 27%
 Bismuth – 15%
 Barium sulphate – 15%
 Sodium borate – 1%
 Liquid: Oil of cloves

Manipulation of Grossman Sealer
 Mixing is done on a sterile glass slab with
sterile spatula.
 After mixing, the cement is carried into
the canal on a sterile smooth broach and
coated around canal walls.
 Cement sets hard on the slab from 6 – 8
minutes; Begins to set in the root canal in
about 10 minutes and achieves a final set
in 90minutes.
 The cement is tolerated relatively well by
periapical tissues and is also germicidal.

ii. Paste-Paste ZOE Sealer Cement
Preparation
Base Paste
 Zinc oxide
 Oleo resins
 Bismuth trioxide
 Thymol iodide
 Oil and waxes
Catalyst Paste:
 Eugenol
 Polymerized resin
 Annidalin

Manipulation
 Two pastes of equal lengths are dispensed
onto a dry glass slab and mixed to obtain
homogeneity.
 It sets within 5 minutes on the slab and in
20 minutes in the root canal.
 A commonly used brand is Tubliseal.
Other ZOE Based Brands
Rickert’s Formula.
Wach’s Sealer.
N2.
Endomethasone N.
“N”: Contain Formaldehyde,
hence risk of toxicity; Brands
not used much.

Properties of ZOE Sealer Cements
Advantages
Easy manipulation.
No dimensional changes.
Radiopacity.
Germicidal.
Ample WT.
Non-staining.
Disadvantages
Not resorbed if excess periapically.
Some degree of solubility.
Fluid ingress.

Modifications of ZOE Cements
1. Resin Modification
 Hydrogenated resin (29%) is added to the
powder.
 10% polystyrene is added to the liquid.
 Other cements have 20% PMMA added
[Intermediate Restorative Material (IRM)].

2. Rosin
 A natural resin from tropical pines.
 Light-brown in color.
 29% is added to Zinc oxide.
 Ground to a fine powder.
 Reduces brittleness.
 Reduces solubility.
 Smoother mix with better consistency.
 Adds compressive strength from 15MPa –
38 Mpa.
 Reduces WT and ST.
 All modern ZOE’s contain rosin.

3. Ethoxybenzoic Acid (EBA) Modified
ZOE
 Substitutes a part of Eugenol liquid with
orthoethoxybenzoic acid:
37.5% Eugenol : 62.5 % EBA
 Fused quartz/alumina is added to ZnO.
 Purpose: higher compressive strength
(90MPa) and abrasion resistance.
 For strong cement set, P:L Ratio = 7:1.
 Lower solubility.
 Can also be used for permanent luting.

Examples:
4) Eugenol Free ZnO Cements
 Especially for patients allergic to
Eugenol, or
 For use as lining under
composites/compomers.
 May contain vanilate esters in place of
the Eugenol component.
 Freegenol (GC)
 Nogenol (COE)
 Temp Bond (Kerr)
 ZONE

5. Other Modifications
 Formulation containing powder made of
of 20 wt% to 40 wt% of fine polymer
particles and Zinc oxide particles that
have been treated with carboxylic acid.
 The rationale is also to improve strength
and abrasion resistance.
 The liquid used in this system is
Eugenol.

Zinc oxide Eugenol Brands
Kalzinol™ by Dentsply (a resin bonded ZOE)

6. Calcium hydroxide Cements
 Presented either as 2 paste system with
radio-opaque fillers, or as,
 A 1 component light-curable base: by
addition of urethane dimethacrylate.
Light cured presentation has superior
properties:
 80MPa Compressive strength.
 10MPa Tensile strength.

Composition
Base paste:
- 1,3 butylin glycol disalicylate.
- Titanium dioxide (inert filler and pigment).
- Calcium tungstate.
- Barium sulphate.
Brown in color.
Confer Radio-
opacity

Composition
Accelerator Paste
 Calcium hydroxide.
 Zinc oxide: Reactant but not a principal
participator.
 Zinc stearate: Accelerator.
 Ethylene toluine sulphonamine:
antibacterial agent.
 Oils: Make it into a paste form.
White in color.

Setting Reaction
 The setting reaction occurs between
Calcium hydroxide and disalicylate
yielding Calcium disalicylate.
 The Calcium hydroxide is present in
stoichiometric excess.

Manipulation
 Equal amount of base and catalyst
dispensed on an oil impervious paper-pad.
 Using a ball-ended instrument, mix to
homogenous color.
 Apply on dentine as a lining.
Mixing time: 5-10 seconds
Working time: 30 seconds
Setting time: 1 minute

Properties
 Basic cement; pH : 11 – 12; used to
neutralize acidic cements,
 Thus, used as sub-liner under cements
like Zinc phosphate.
 Ideal to inhibit microbes esp. those found
in carious dentine.
 Poor mechanical strength:
 Compressive = 6 – 10 MgN/m2.
 Tensile = Very low (almost 0).
 High solubility in water.

Properties (cont’d)
 Stimulates formation of reparative dentine
and so is applied in instances of pulpal
exposure (direct pulp-capping), or near
pulpal exposure (indirect pulp-capping).
 Due to its high pH, it causes irritation to
the pulp.
 Necrosis of cells adjacent to the cement,
and transformation of mesenchymal cell
into odontoblasts which start laying down
reparative dentine.
 Procedure not always successful.

Application as Cavity Liner
 Ca(OH)2 used as a liner is suspended in a
solvent carrier with a thickening agent.
 When placed on the pulpal floor, the solvent
evaporates leaving a thin film of Ca(OH)2.
 The liner does not contain significant
strength or thermal insulation capability.
 But it can neutralize acids that migrate
towards the pulp, and in the process, can
induce the formation of reparative dentine.
 Can be used as a direct pulp-capping
material.

Applications
1. Used principally as cavity liners and
bases.

Applications
2. Subliner.
3. Pulp-capping.
4. Apexification.
5. Temporary luting cement.
6. Non-setting Ca(OH)2 for root canal
dressing.
7. Endodontic sealer cement.

Non-setting Calcium hydroxide
 Used in root canals as intra-canal dressing
material between endodontic appointments,
– eliminate microbes, then later washed off.
 Also for managing root resoption.
Usual formulation: Ca(OH)2 and some
binders e.g. Methyl cellulose.
Other formulation: Powder mix with distilled
water.

Ca(OH)2 Based Sealer Cements
 Used in endodontics.
 Favoured due to their ability to :-
i. Induce apical closure.
ii. Inhibit root resorption.
iii. Create as good a seal as ZOE.
iv. Less toxic than ZOE sealers.

Ca(OH)2 Based Sealer Cements (cont’d)
 They are presented as paste/paste.
 They set via a reaction between calcium
hydroxide and a salicylate ester-aldehyde.
 The base paste mainly has 35%calcium
hydroxide while the reactor paste is 25%
ethyl salicylate and fillers making up the
remaining bit.
 Ca(OH)2 has a pH of 12.5 and is radiopaque.
 It has been recognized for being antibacterial
due to the high pH and its ability to stimulate
bone healing and root formation.

Ca(OH)2 Based Sealer Cements (cont’d)
 Besides being used as an adjunct root
canal filling materials, it has also been
employed for:
- Apexification: Cement is placed in
root canal’s apex.
- Apexogenesis: Histological
analysis later shows apex formed is a
mixture of hard tissues
:dentine, cementum and bone.

Calcium hydroxide Brands
Setting:
 Dycal
 Calcimol
 Cavitec
 Prisma Dycal (light cured)
Sealer Cements: - Apexit - Metapex.
- Sealapex
Non-Setting:
 Ultracal
 PD Calcium hydroxide

Calcium hydroxide Brands
PRISMA VLC DYCAL™ – Light Curing

7. Resin Cements
 Polymeric cements that set via
polymerization reactions.
 Resin cements are essentially flowable
composites of low viscosity.
Applications
Cementation of:
 Crowns.
 Resin bonded bridges.
 Inlays and onlays.
 Orthodontic brackets.
 Veneers.
 Posts and Cores.

Applications of Resin Cements
Resin bonded bridges
A Maryland Bridge

Applications of Resin Cements
Cementing Orthodontic Appliances

Composition and Chemistry
 Similar to that of resin based composite
filling material: resin matrix with silane-
treated inorganic fillers.
 Fillers: silica or glass particles &/or colloidal
silica used in micro-filled composites.
 Require a dentine bonding agent in most
instances to promote adhesion to tooth
structure e.g in luting a crown.
 Only exception is in anterior veneer tooth
preparation which is usually only enamel
deep.

 The adhesive monomer incorporated into
the resin monomer and cements include:
i. HEMA
ii. 4 – META(Methacryloxyethyl trimetillic
anhydride): a liquid adhesive that
acquires cement consistency by
incorporating polymer beads.
 No separate bonding agent is needed.
iii. An organophosphate e.g. MDP (10-
methacryloxydecamethylene phosphoric
acid).

Polymerization
 By conventional chemical cure system
with an organic peroxide e.g. BPO as an
initiator.
 Light activation; addition of an alpha
diketone and an aliphatic amine: applied
where curing is practical e.g. through thin
porcelain veneers (like Porcelite), resin
based prostheses that are less than
1.5mm in thickness, and plastic and
ceramic orthodontic appliances.
 Dual cure.

Properties of Resin Cements
 Insoluble in oral fluids.
 Monomer is a pulp irritant, thus line with
Ca(OH)2 or GIC if dentine thickness ≈
0.5mm or less.
 Compressive strength: 180-265MPa.
 Tensile strength: 30-63MPa.
 Viscosity: Low to high.
 Film thickness: 13-20 μm.
 Shear bond strength to enamel: 15-
35MPa.
 To dentine: 5-35MPa.

Manipulation
 Ensure clean, dry area of tooth surface.
 Condition with etchant.
 Prime.
 Bond.
 Remove excess cement immediately after
prosthesis is seated.
 Light cure if indicated, usually for no less
than 40 seconds.
 The dual cure should not be used for any
light transmitting prosthesis thicker than
2.5mm (use chemical cure for such).

Metallic Prosthesis
 Roughened by grit blasting with 30-50pm
alumina particles at an air pressure of 0.4-
0.7MPa, or by electrochemical etching.
 Surface oxide layers contribute to bonding in
base metals when MDP or 4-META based
resin is used.
 Electrochemical coating of tin (≈0.5pm) on
noble metals is done to achieve this oxide.
 A silica coating can be used to achieve the
same bonding strength values to noble
metals and base metal alloys as grit blasting
and electrochemical etching.

Orthodontic Brackets
 Ensure proper isolation and etching of
enamel.
 Apply a bonding agent on the enamel.
 Metallic bracket has a mesh for mechanical
retention.
 Etch ceramic brackets and coat with an
organosilane analogous to the coupling
agent of fillers to resin matrix of composites.
 Prime plastic brackets in a solvent containing
methylmethacrylate monomer.

Advantages
i. Only cement that is insoluble in oral
fluids.
ii. High strength.
iii. Viscosity suitable for luting.
iv. Various shades; color can be matched to
the tooth.
v. Dual cure.
vi. Radio-opaque.
vii. Easy to manipulate.

Disadvantages
i. Disintegrates if used as a gap filler.
ii. Self cured form is difficult to trim.
iii. Expensive.
iv. Irritation to pulp.
v. Stains.
vi. Poor wear if not highly filled.

8. Mineral Trioxide Aggregate
 Developed as a root end filing material in the
1990’s.
 Commercially available as Pro root MTA in
either grey or white form; their difference
being the conc. of Al, Mg and Fe cmpds.
 Grey MTA contain the tricalcium
alluminoferrite phase that is lacking in White.
Constituents
 MTA is a silicate cement.
 50-75% by wt Ca(OH)2.
 15-25% silicon dioxide.

 When these raw material materials are
blended they produce:
i. Tricalcium silicate.
ii. Dicalcium silicate.
iii. Tricalcium aluminate.
iv. Tetracalcium aluminoferrite.
v. Calcium sulphate.
vi. Bismurth oxide.
 On addition of water the cement
hydrates to form silicate hydrate gel.

Properties
 Compressive strength of 40-70MPa(equal
to IRM&Super EBA,but lees than AgF).
 pH of 12.5.
 ST = 2-4 hrs.
 Sets in moist environments.
 Low solubility.
 Resists marginal leakage and bacterial
invasion.
 EXCELLENT biocompatibility.
Packaged in 2gm pellets and sterile water.

Manipulation
 Mix to obtain a grainy, sandy mixture and
the apply with a messing gun.
 Requires moisture to set; desiccation is
contraindicated.
 Might even have to place wet cotton pellet
in contact with the MTA to facilitate setting.
 Takes 4 hours to set; this may limit its use
in endo.

Applications
1. Root end filling.
2. Pulpotomy.
3. Apexification.
4. Perforation repair.
5. Pulp capping.
6. Repair of resorption.
Disadvantages
 Expensive.
 Difficult to remove.
 Technique sensitive.
 Long setting time.
 Grey colored cannot be used in anterior teeth.

Comparison with Portland Cement.
MTA Portland Cement
•Presence of Bismuth oxide •Bismuth oxide absent
•Less gypsum •More gypsum
•Shorter setting time •Longer setting time
•Less aluminum and heavy
metals; less toxicity.
•More aluminum and heavy metal
ions; more toxicity.
•Smaller uniform particle size. •Range of particle size
distribution.

“If anyone
thinks he has
acquired
knowledge of
something,
he does not yet
know it just as
he ought to
know it.”
-1 Cor 8:2
… So, READ
some more!!

Dental Cements by Silas M. Toka

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