Hello, my dear friends. Welcome back to
the channel and this is your friend.
Dr Suresh Shenvi.
I hope that you are liking the current
ongoing series on dental cements
and today we are discussing about zinc
oxide eugenol cement.
Zinc oxide regional cement is mostly
popular as a temporary
restoration and it has its own special
advantages and disadvantages which will
be often asked in the exam.
The main advantages being its ability to
give the best biological seal
and the disadvantage being its
irritating potential because of the
eugenol.
We'll try to learn more about the other
properties
and i hope that you will continue
watching this video so that you
understand the topic better.
In the market, zinc oxide eugenol
cement is available in two forms. That is
the powder liquid and it is also
available
as the paste form for operative
dentistry.
Zinc oxide regional is classified into
four categories.
The type one being used for temporary
cementation,
The type 2 is used as a permanent
cementation material,
The type 3 was mostly made for temporary
filling
and as a base.The last type, that is the
type 4 was mostly used as a liner and
I know at this point you may also ask me
that
why would somebody use zinc oxide
regional cement as a liner
when we have better materials like
calcium hydroxide?
We'll discuss it in the properties,
Let's discuss the composition of the
cement.
The powder here too has zinc oxide as a
major component. Please note, although you can obtain zinc
oxide from various other materials but
generally it is obtained from heating
zinc hydroxide. That's because when you
get it from zinc hydroxide the powder, it is
found to be more reactive. Along with this they have also added
zinc acetate and zinc propionate to
accelerate the setting reaction. The
liquid consists of mostly eugenol
which can react with the powder and that
reaction is possible because
it has a benzene ring and this benzene
ring is
reactive with zinc oxide. However eugenol
can irritate and also produce allergic
reactions
when it reacts with the skin proteins
and that's why
it is often replaced by oil of cloved
which consists
of 70 to 85 percent of eugenol
but has less potential to cause
irritation. Although the liquid also
contains glycerin
or glycol as retarders for the setting
reaction
but it's the water from the liquid which
has a major role
on the setting reaction and let's
understand about it.
in the setting reaction segment. This
cement also sets because of
acid base reaction and the powder is
basic
and eugenol is acidic in nature but
please note that zinc
oxide cannot directly react with eugenol.
It has to be first converted to zinc
hydroxide
and to convert zinc oxide to zinc
hydroxide
it needs water or acetic acid and acetic
acid is better for
this reaction. Once the zinc hydroxide is
formed
this cannot act with eugenol. For this
reaction too
we need water and when you have water
the zinc hydroxide will react with
eugenol and form a chillate called as
zinc eugenelate and release the water
as a by-product. So if you see the
setting reaction we need water to
initiate the reaction
and we also get water as a by-product
and this water will again
initiate the reaction that's why this
reaction is called as autocatalytic.
Let's discuss
about the properties of the zinc oxide
eugenol cement. As discussed in my pulp capping video, we
need three things for the progression of caries
one is the tooth,
second is the organism,  third is the
substrate or a food
and when you use zinc oxide eugenol as a
temporary material for indirect pulp
capping it is found to have a very good
initial
seal to prevent the nutritions from
reaching the organism
and also since eugenol is constantly
released from the cement in the deeper
portion
it has found to have good antimicrobial
property. So in this triad
we are cutting down the nutrient and the
organisms, that's why the caries will stop
progressing. However this was also used initially as
a pulp capping agent in diet pulp capping
but since it doesn't have the ability to
stimulate the reparative dentin
formation,
it was soon discontinued once the
calcium hydroxide
became popular. Also, note in a deeper
cavity where there is a limited amount of
remaining dentinal thickness this zinc
oxide eugenol can be really
beneficial for two reasons.
First being its ph that is seven and it
is considered as a neutral. That's why it is far beneficial for the
pulp iin contrast to the other cements like
glass cenomaror zinc phosphate or zinc
polycarboxylate, since they have a
lower ph . The second advantage is its
obtundent property on the pulp.
When it is given in deeper cavities, it
is slowly releasing
a very low concentration of eugenol
which will pass through the dentinal
tubule
and reach the pulp and it will try to
suppress the inflammatory mediators
like the prostaglandins, And that's why
this was very popular
in the olden days for treatment of
reversible pulpitis,
where the main aim was to reduce the
inflammation of the pulp.
If you compare the solubility of cements
in the oral cavity zinc oxide eugenol
cement is the most
soluble out of all the cements which is
used in dentistry. The other disadvantage is that it
doesn't have any
fluoride releasing property. That's why
it doesn't possess any
anti-cariogenic effect. The bonding too
is not special. It doesn't have any chemical or micro
mechanical bonding. It has just mechanical retention in
the cavity preparation. Although the strength of the zinc
oxide eugenol cement can range from 3
mpa to 55 mpa, but since it is mostly
used as a temporary material, the
strength should be around 35 mpa so that
you can
remove it while doing a permanent
restoration. However zinc oxide eugenol  cement also
has negative effect on composite
restoration.
The first situation is where you give it
as a base below a composite restoration
and it is found that
the zinc oxide eugenol will prevent the
curing of composite. So that's why
zoe is contraindicated as a base
material below the composite restoration. Second, if you are used this as a
temporary material and the next
appointment
if you are removing and placing the
composite, it is found that there is some
amount of eugenol which is remaining
in tooth and this will prevent the
composite or bonding agent from
attaining a high bond strength. So the
take home message
is that if you are doing a composite
restoration , you can go for
glass ionomer cement as a temporary
restoration
and then give a composite in the next
appointment. The same concern is also present in
veneer cementation. Suppose
before giving permanent cementation of
veneering you gave a temporary
with zinc oxidizing all cement in future
the resin cement for permanent
cementation
will have a lesser bond which is
sometimes really damaging
for the long term health of the
restoration. So what is the solution?
Nowadays
in market you have non-eugenol
containing
zinc oxide cement which can be
beneficial
in such situation whenever a resin
bonding
material is involved. Coming to the last
aspect that what modifications
are done in zinc oxide regional cement
and why were they done?. 
We already discussed the non-eugenol
containing zinc oxide cement but the
second major change
was in order to increase the strength
there are situations where you want to
wait for
more than six to eight months before
giving a permanent restoration and in
that situation if you are giving the
normal zinc oxide regional cement as a
temporary,
it will dissolve or it may break because
it doesn't have sufficient strength.
Although you can increase the strength
by incorporating more powder
into the cement liquid, however if you
have
a zinc oxide regional modification with
better strength it will be really useful
in this scenario
and in order to improve the strength, two
type of modification were done.
The first modification is popularly
known as
IRM that is intermediate restorative
material
in which the powder has additions of
poly methacrylate and this definitely
increased the strength biocompatibility
of the cement compared to the unmodified
zinc oxide eugenol cement. However
please note that IRM is bit difficult to
remove than the zinc oxide original
cement. The second modification is
popularly known as
Super eba, in which the main aim of
introducing this modification was to
increase the strength but also to alter
the setting time.
This was modified by substituting the
eugenol partially with ortho ethoxy
benzoic
acid and the powder also had quartz or
aluminium oxide. Please note that super eba is considered
to be one of the best material for
retrograde root filling
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