Pars LD 2
Pars LD 2
Pars LD 2
tissues.
to be packed on it.
material.
c.Electrical insulation under a metallic restoration to minimize
galvanic effects.
caries.
sufficient low viscosity to give a low film thickness and should have
the restoration.
Classification of Dental Cements:
by:
- Craig.
- Skinner.
- Combe.
- William O’Brien
CRAIG:
FUNCTIONS CEMENTS
Final cementation of completed Zinc phosphate, zinc
restorations. silicophosphate, reinforced zinc
oxide eugenol, zinc
polycarboxylate, glass ionomer.
Temporary cementation of Zinc oxide eugenol, noneugenol
completed restorations or zinc oxide.
cementation of temporary
restorations.
High-strength bases Zinc phosphate, reinforced zinc
oxide eugenol, zinc
polycarboxylate, glass ionomer.
Temporary fillings Zinc oxide-eugenol, reinforced
zinc-oxide-eugenol, zinc
polycarboxylate.
Low-strength bases Zinc oxide-eugenol, calcium
Liners hydroxide.
Calcium hydroxide in a suspension.
Varnishes Resin in a solvent
Special applications:
Root canal sealer. Zinc oxide-eugenol, zinc
polycarboxylate.
Gingival tissue pack Zinc oxide eugenol
Surgical dressing Zinc oxide eugenol, zinc oxide
preparation
Cementation of orthodontic bands Zinc phosphate, zinc
polycarboxylate
Orthodontic direct bonding. Acrylic resin, composite resin.
SKINNER
E.C. COMBE:
b. Polymerizing materials:
i. Cyanoacrylates.
ii. Dimethacrylate polymers.
iii. Polymer-ceramic composites.
c. Other materials.
i. Calcium hydroxide.
ii. Guttapercha.
iii. Varnishes.
Zinc phosphate
Zinc polycarboxylate
Zinc oxide-eugenol
Resin
Glass ionomer
William J. O’Brien:
Adhesive 4-META
the powders are either zinc oxide or aluminosilicate glasses while the
LIQUID
Phosphoric
acid
POWDER Polyacrylic acid Eugenol
aluminosilicate
Glass-ionomer
glass
cement
Zinc Phosphate Cement
One of the oldest and most widely used cements, zinc phosphate cement is
hopeite, or tertiary zinc phosphate, are found on the surface of the cement.
Composition
Powder
ZnO 90.2%
MgO 8.2%
Si02 1.4%
Bi2O3 0.1%
into the fine powder. The smaller the particle size, the faster the set
of the cement.
Liquid
H3PO4 38.2%
H2O 36.0%
Zn 7.1%
Al 2.5%
The water content of most liquids is 33%±5% and controls the ionization
of the acid, which in turn influences the rate of the liquid-powder reaction. The
phosphoric acid reacts with zinc oxide which the aluminium or zinc phosphate
ADA Specification No.8 calls for a film thickness of less than 25 microns.
Type II: used as a base and for luting orthodontic bands;
ZnO + ZH 3 PO 4 Zn (H 2 PO 4 ) 2 + H 2 O
ZnO + Zn(H 2 PO 4 ) 2 + 2H 2 O Zn 3 (PO 4 )z 4H 2 O (hopeite)
When the powder is mixed with the liquid, the phosphoric acid
attacks the surface of the particles dissolves the zinc oxide forming
acid zinc phosphate. The aluminium reacts with the phosphoric acid
Advantages
Long record of clinical acceptability.
Disadvantages
PROPERTIES
1. Compressive strength:
strength.
2. Tensile strength :
ZnPO 4 cement when properly manipulated exhibit a diametral
3. Modulus of elasticity:
10 6 psi).
of time. This shows that the other factors (like wear, abrasion,
in dilute organic acids like lactic, acetic, and especially citric acids.
5. Film thickness:
not more than 25µm for Type II – film thickness not more than
40µm.
size, less is the film thickness. The thickness is lesser than the
7. Adhesion property:
between the casting and the tooth also is the factor, in the
8. Biological properties:
lower and remains lower for a longer period of time. Any damage
to the pulp, from acid attack by ZnPO4 cement, occurs during the
first few hours after insertion. A thickness of dentin as great as
occur.
pulp with:
10.Optical properties:
Manipulation
ZnPO4 cements:
be kept dry.
in oral fluid.
should be discarded.
powder into the liquid than normally occurs. This offsets the
Uses:
1) Prefabricated and cast posts.
2) Metal inlays and onlays.
3) Crowns and FPDS.
4) All ceramic creams.
Recent Products
Product Working Setting
Composition Shelf life
name time time
A 1970 study2 of nearly 800 crown and bridge units cemented with zinc
Zinc polycarboxylate cement, also known as zinc polyacrylate cement, was one of
the first chemically adhesive dental materials. Introduced by Smith in 1968. The
adhesive bond is primarily to enamel although a weaker bond to dentin also forms.
This is due to the fact that bonding appears to be the result of a chelation reaction
between the carboxyl groups of the cement and calcium in the tooth structure;
hence, the more highly mineralized the tooth structure, the stronger the bond.
When zinc oxide and polyacrylic acid are mixed, hydrated protons formed
from ionization of the acid attack the zinc and magnesium powder particles.
This causes the release of zinc and magnesium cations which form
Composition:
being:
– CH 2 – CH – CH 2 – CH –
| |
C=O C=O
| |
O O
| |
H H
Powder
- Zinc oxide
- Magnesium oxide.
- Other oxides like bismuth and aluminium.
- Stannous fluoride.
- Basic ingredients.
- Principle modifier.
that have been sintered and ground to reduce the reactivity of zinc oxide.
anticariogenic properties.
Liquid:
In these cements, the polyacid is freeze dried and the powder is then
mixed with the cement powder. Water is used as the liquid. When the
powder is mixed with water, the polyacrylic acid goes into the solution and
dissolution. By the acid that releases zinc, magnesium, and tin ions, which
bind to the polymer chain via the carboxyl groups. These ions react with
– CH 2 – CH 2 – CH 2 -
| |
C C
O OH HO O
Zn
O OH HOO
C C
| |
– CH 2 – CH 2 – CH 2 –
PROPERTIES
thickness, acid erosion, arsenic and lead content, and a minimum value
2) Viscosity
brittle than ZnPO4 cement and this hard to remove the excess
after cementation.
start of mixing.
The temperature of the cool slab can cause polyacrylic acid and to
thicken and thus make the mixing procedure more difficult. Therefore it
has been suggested that only the powder should be refrigerated before
mixing as the reaction occurs on the surface and the cool temperature
5) Film thickness
the action of spatulation and seating with a vibratory action reduce the
vivo. Solubility in water at 1 day varies from 0.12% to 0.25% for typical
maximum rate of acid. Though the solubility in water is low, but when it
7) Biologic considerations:
or soft tissues has been found to result only in a very mild response. The
They are less irritant to the pulp than ZnPO4 cement. This is
because,
that of ZnPO4.
b) Penetration of polyacrylic acid into the dentinal tubules is
8) Adhesion
The bond strength enamel ranges from 3.4 to 13.1 Mpa and that to
dentin is 2.07Mpa.
9) Optical properties:
MANIPULATION:
Areas of major concern are the mixing of the cements, the surface
preparation of the prosthesis, the nature of the tooth surfaces receiving the
e) The liquid should not be dispensed before the time when the
working time. The mix appears quite thick, but this cement
will flow readily into a thin film when placed under pressure.
Uses:
teeth.
Advantages
Disadvantages
Certain types of zinc oxide, when mixed with eugenol sets to a hard
cement that is compatible with the hard and soft tissues of the mouth.
general, they are cements of low strength. Also they are the least irritating
of all dental cement, and are known to have an obtundant (sedative) effect
on exposed dentin.
To improve the strength many modified zinc-oxide eugenol cements
Classification:
restorative materials.
Mode of supply:
Commercial names:
1. Unmodified
- Tempac – Type III.
- Cavitic – Type IV
- Tempbond – Type I.
4. Noneugenol
- Neogenol – Type I
- Freegenol – Type I
Composition
Powder
Liquid
Setting Reaction
As the basic components of the cement are zinc oxide and eugenol,
the setting reaction and microstructure are the same as that of the
impression pastes.
In the first reaction hydrolysis of zinc oxide to its hydroxide takes
place. Water is essential for the reaction to proceed (Dehydrated zinc oxide
chelate.
Factors affecting setting time: The complete reaction between zinc oxide
and eugenol takes place in about 12 hours. This is too slow for clinical
convenience.
1. Manufacture: The most active zinc oxide powders are those formed
heating at 300°C.
2. Particle size: Cements from powders containing smaller zinc oxide
Lower temperature, e.g., cooling the glass slab, slows the reaction.
6. Powder to liquid ratio: The higher the ratio, the faster the set.
Properties:
1. Mechanical properties:
a. Compressive strength:
(Type I), and cavity lining (Type IV), will have a lower strength.
particle size, the stronger the cement. The strength can also be
c. Modulus of elasticity:
use as bases.
2. Thermal Properties:
a. Thermal conductivity.
cementation.
0.04%wt.
The solubility of the set cement is high, the highest among the dental
4. Film thickness:
5. Adhesion:
reasons why they are not often used for final cementation of dental
restoration.
6. Biological properties:
as mild.
pH is 6.6 to 8.0
Manipulation
liquid is dispensed onto a cool glass slab or paper pad. The bulk of the
instruments.
Equal lengths of each paste are dispensed and mixed until a uniform
color is observed.
and heat.
MODIFIED ZINC OXIDE EUGENOL CEMENTS
EBA-ALUMINA MODIFIED CEMENTS
Composition:
Powder Liquid
Zinc oxide - 70% EBA - 62.5%
Alumina - 30% Eugenol – 37.5%
Properties:
Manipulation:
After dispensing the powder is incorporated into the liquid in bulk and
kneaded for 30 seconds, and then stopped for an additional 60 seconds with
1. Luting agent.
2. As base.
4. As cavity liner.
Composition:
Powder Liquid
Zinc oxide Eugenol
Finely divided natural or Acetic acid – accelerator
Synthetic resins Thymol – antimicrobial agent.
resins, if present, may react with zinc oxide, strengthening the matrix.
time.
Properties:
Manipulation:
The proper powder / liquid ratio is dispensed on a dry glass slab. The
powder is mixed into the liquid in small portions with vigorous spatulation.
Working time: These cements have a long working time.
liquid is mixed with zinc oxide powder. It has been claimed that these
in pulp capping and root canal therapy. Another product also contains
Advantages
Disadvantages
Weak.
Opotow Alumina EBA (Teledyne Getz), Super EBA (Bosworth), and Fynal
(LD Caulk).
Resin Cement
As a general rule, resin cements are the best choice for luting ceramic
with resin versus other types of cements; clinical studies; and laboratory
resin cements were first developed in the early 1950s for use as crown and
bridge luting agents but had poor physical properties (high polymerization
content. Modern products are more highly filled and have better physical
Visible light-activated cements are generally reserved for the luting of cast
transmit light. The chemicallyactivated forms are used for the cementation
(Bisco).
Composition
Advantages
Low solubility
Disadvantages
whose manufacturers claim they have the ability to chemically bond to both
tooth structure and metals. These cements contain adhesive monomers such
as MDP, HEMA, and 4-META and include such products as Panavia 21 (J.
4-META.
for restorations when minimal retention form exists because several studies
have found these cements to be more retentive than zinc phosphate, glass-
the product was marketed from 1983 to 1994 and consisted of a powder and
a liquid. The powder was a BIS-GMA based resin filled to 76% by weight
with quartz particles. Also present in the powder was a benzoyl peroxide
stabilizers. Also in the liquid was the bifunctional adhesive monomer 10-
Waals forces).
The new product, Panavia 21, differs from its predecessor because it has an
applications. The primer comes in two separate bottles and is mixed just
Morita claims that the primer enhances bond strength to dentin which had
been relatively low with the old product. When using Panavia 21 to bond
resin-bonded fixed partial dentures to tooth structure, the metal should not
mechanical irregularities in the metal trap air and water which inhibit
Panavia 21's polymerization. If the casting is a base metal, simply air
abrade it with 50-micron aluminum oxide at from 60 to 100 psi and then
the surface.
the product. If the enamel has been prepared, only primer is applied; no
etching is necessary.
Dentin is treated by applying the primer for 60 seconds and then drying it.
polyethylene glycol gel, Oxyguard II, must be usedto cover the exposed
(opaque) which is opaque. All three shades are said to be radiopaque. Film
(4-META, MMA), catalyst (tributyl borane), and tooth colored and clear
powders (PMMA). When using this cement for the luting of resin-bonded
fixed partial dentures, prepare the casting surface as described for Panavia;
the tooth surface should be treated with the enamel etchant or dentin
from chemical curing.7 It is, therefore, very important to ensure that they
Generally, film thickness has been reduced for the resin cements due to the
8
use of smaller filler particles and incorporation of diluent monomers,
used improperly.
It is recommended that patients be advised against loading restorations
strengths are weak and need a period of 24 hours to fully mature. Generally,
the patient should be told to be careful to avoid loading for the first hour. It
GLASS-IONOMER CEMENTS
and developed by McLean and Wilson during the 1970’s. This class of
restoration of Class V erosion lesions and Class III cavities, fast setting
liners and bases for attaching composite resins to tooth preparations, fine
grained luting agents, fissure sealants, and metal reinforced core build up
materials.
These cements have combined properties of silicate cements and
because, the powder is glass and the setting reaction and adhesive bonding
to tooth structure is due to ionic bond. This cement is also referred to as:
- Poly (alkenoate) cement.
- GIC.
- ASPA (alumino silicate polyacrylic acid).
groups, generally by the order of 5% to 10%. This does not clearly apply to
the components of the glass ionomer cement and therefore the term glass
polyalkenoate cement was devised. However, unlike the term glass ionomer
polyphosphonate etc.
Classification:
Type I glass ionomer cements are used for the cementation of cast
Composition:
Powder
Weight %
Silica (SiO 2 ) - 41.9
Alumina (Al 2 O 3 ) - 28.6
Aluminium fluoride (AlF 3 ) - 1.6
Calcium fluoride (CaF 2 ) - 15.7
Sodium fluoride (NaF) - 9.3
Aluminium phosphate (AlPO 4 )- 3.8
- Tartaric acid.
- Water.
for gelation.
reaction medium and it hydrates the reaction products. The amount of water
in the liquid is critical. Too much water results in a weak cement while too
and glass powder in one bottle and water or water with tartaric acid in
another bottle as the liquid component. This extends the working time.
When the powder is mixed with water, the polyacrylic acid powder goes
into solution to reconstitute the liquid acid. Then the chemical reaction
proceeds as for powder and liquid. These cements have a longer working
time with a shorter setting time and are occasionally referred to as water
When the powder and liquid are mixed together, the acid liquid
attacks the surface of the glass particles. Thus, calcium, aluminium, sodium
and fluoride ions are leached into the aqueous medium, probably in the
progressive cross linking occurs and the set cement becomes stronger and
less moisture sensitive. The salts hydrate to form a gel matrix and the
unreacted glass particles are sheathed by silica gel which arises from
It serves as the reaction medium initially, and it then slowly hydrates the
cross linked matrix, thereby increasing the strength of the material. The
cements are kept isolated from the ambient air, the loosely held water will
slowly become tightly bound over time. Of the same mixes are exposed to
ambient air without any covering, the surface will crack and craze as a
stage can cause dissolution of the matrix forming cations and anions to the
surrounding areas. So, the cement must be protected from water changes in
structure during placement and for a few weeks after placement if possible.
Type I glass ionomer cement has a working time ranging from 3-5
minutes. The water settable cements have somewhat longer working times.
The setting time for the different brands of cement is usually between 5 and
9 minutes. The water added cements have a more rapid initial set than those
Properties:
water during the first 24 hours is high. It is important that the cement
period. After the cement has been allowed to nature fully, it becomes
one of the most resistant of the non resin cements to solubility and
polyacids and the calcium in the opacity of the enamel and dentine.
The bond of enamel is always higher than that to dentin probably due
hazardous, because of the high acidity and slower set, which is due
precedence over other matters, such as the potential for adhesion that
ensures a strong bond to the tooth structure. The smear layer on the cut
left intact to act as barrier to the penetration of the tubules by the acid
component of the cement. All the deep areas of the preparation should
fluoride over an extended period time. The adjacent enamel and more
at the margins. In addition, due to its adhesion effect they have the
MANIPULATION
and then dried but not dehydrated. Under dessication opens up the tubules,
As the cement does not bond properly to the metal in the chemically
cleaned cementation should be carried out before the cement loses its
glossy surface. Glass ionomer like ZnPO4 becomes brittle once it has set,
PRECAUTIONS:
1) The mix should have a glossy surface as this indicates that the during
the reaction the pressure of residual polyacid has not been used up in
the setting reaction. This ensures adhesive bonding to the tooth. The
fracture toughness and resistance to wear and get maintain the potential for
Properties:
1) Mechanical properties:
conventional cement.
- Fracture toughness is the same as conventional GIC.
2) Anticariogenic properties:
anticariogenic capability.
coated. The admixed cement release more fluoride than Type II GIC,
since the metal filler particles are not bonded to the cement matrix and
this, pathways for fluid exchange are created, which greatly increase the
Clinical considerations:
restored with cast crowns but not in cases where the cement
were improved light cure glass ionomer cements have been used as lining
Lin et al (1992) and Smith (1992) gave evidence that light cured
cured resin modified glass ionomers as luting agents for composite and
processes that can overcome these two inherent drawbacks and allow the
4) Resin-ionomers.
5) Compomers.
Composition:
Liquid: Water
methacrylate monomers.
Setting reaction:
final maturity and strength are achieved by the slow acid base reaction. The
overall water content is less for this type of material to accommodate the
1. Physical properties:
cements are used as liners with a higher P:L ratio. This is due to the
lower water and carboxylic acid content which reduces the ability of the
dimensional changes.
6. Clinical considerations:
process.
7. Solubility is low.
GIC (pH-2).
Applications:
1) Metal or porcelain fused to metal crowns and freed partial dentures.
2) Liner.
3) Fissure sealant.
4) Base.
5) Core-build up.
6) Restoration.
Properties:
Property Resin ionomer Compomer
1) Film thickness. > 25µm > 25µm
2) Working time. 2-4 min. 3-10 min.
3) Setting time. 2 min. 3-7 min.
4) Compressive strength. 40-141 Mpa 174-200Mpa
5) Modulus of elasticity. n/a 17 Gpa
6) Pulp irritation. High High
7) Solubility. Very low Very low
8) Microleakage. Very low High to very high
9) Removal of ions. Medium Medium
10) Retention. N/a Moderate
11) Anticariogenic High High
Advantages
Anticariogenic effect.
Low solubility
Disadvantages
The latest development involving the use of glass ionomers as luting agents
They have greater tensile strength and are less brittle. In addition, they
12
release at least as much fluoride as traditional glass ionomers, are less
Although the three brands are similar in that they are all self setting (i.e.,
self curing), differences exist between them in many ways (e.g., how the
prepared tooth is treated prior to luting and the number of clinical uses for
using RelyX. With Fuji Plus, however, the prepared tooth surface must be
is used only for luting, Fuji Plus is used for luting as well as a liner/base.
FujiCem is the only one of the three that is a twopaste system; the other two
are powder and liquid. It is important to know that these cements should not
water sorption.
Additional Cement Facts
Cement Rankings
cement dissolves when the solvent attacks the cement's matrix, however
with zinc polycarboxylate cements, both the matrix and powder particles
are attacked.
effects:
pH: increases
viscosity: increases
have found that increasing the roughness of the internal surfaces of castings
One way to reduce the potential for post-cementation sensitivity with zinc
the prepared tooth prior to luting. Recent research has found that this type
Zinc Phosphate Cement: a good choice for routine prosthodontic use; has a
postcementation sensitivity.
12
Glass-Ionomer Cement: excellent for general prosthodontic
Cem Maxicap.
References
1401.
Dent 1996;21:196-202.
11&12.
13
486.
15. Felton DA, Kanoy BE, White JT. The effect of surface
16. Swift EJ, Lloyd AH, Felton DA. The effect of resin
1997;128:195-200.