Lecture 10, Dental Cements II (Script)

8/3/2019 Lecture 10, Dental Cements II (Script)

1/13

1|P a g e


2/13

CEMENTS (2(Dental Material II Lecture # 10

Please refer to the slides while reading the script because the doctordidn't say everything written in the slides.

-Surgical Addressing: (Slide24(

Purpose for using cements as dressing:

Protection and support of surgery site.

Help to control bleeding.

Provide comfort for patient.

Material that are used:

1.Does not contain eugenol ( they can be zinc oxide but not eugenolbecause eugenol can cause irritation) so these preparation usually

don't have any eugenol of them.

2.They mixed to soft putty like consistency.

You need addressing to protect the wall site, you want to protect any

irritation to the surface and support tissue, so some cement can be useat the surgical dressing.

Soft place on the wall site, retain their and then the patient come back tobe remove after a week, two or whatever depending on surgicaldressing.

2|P a g e


3/13

So this dressing should be:1-smooth, it is shown in this picture. And should be not too bulky,

otherwise it will annoy the patient.2-it should be retain so it will not fall over all the time.

3-It should cover the surgical site with minimal extension >> overextension will bother the patient.

4-It should lock interdentally like so to provide retention.

The general properties of the dental cement:

It depend on the type of cement each cement has specific propertiesdepend on its component:

Strength: depends on (powder : liquid ratio(so brittle material usually has high compressive strength but low

tensile strength.

Solubility: the lower the powder : liquid ratio is the higher solubility,and the cement will be weaker.

And the cement with high solubility can lead to micro leakage, irritationto the pulp, sensitivity, recurrent carries ..etcFor example GIC have higher solubility compared to the resin cement.So GIC more susceptible to corrosion than the resin, & GIC can be

exposed to micro leakage more than resin.

Viscosity : again the higher the powder the greater the viscosity, thisimportant when we talk about the luting cement.

So luting cement need to have low viscosity so that they can flow

and cover the entire surface for the prepared tooth for optimalretention.

Now if you want to increase the viscosity just you need to increase theamount of powder which it's mixed to the liquid.

Biocompatibility : it depends on many thing, for example: cementthat have initial acidic PH can cause some irritation for some timeuntil the PH become neutral, like GIC and later on we will see zinc

phosphate cement, when we mix them, we mix a powder within acid"polyacrylic acid or carboxylic acid "it is an acid so the initial PH is

3|P a g e


4/13

low (2,3 or 4) it needs some time like 24 hour or 48 hour to become 6or 7( neutral) so this acidity can cause biocompatibility.

Now material that contains fluoride have good biocomtability. Why?because they are very special. For example some cement like GIC theyhave fluoride, which is good because it will prevent caries, so this willimprove the biocompatibility.

Retention : some are retained micromechanically like resin cement.Some are retained chemically like GIC, again depend on cementitself.

Esthetics : resin cement or resin modified cement have shadesavailable and they have better esthetic proprieties compared to GIC.

I mean, we know that the resin is available with more shades ofthe resin and therefore the best in terms of esthetic than cement, so forexample if we are using the veneers to change the shade of the tooth wecan use the cement underneath that has similar shade to the tooth, thatmean we can control the shade of the veneers, shade of the crown andwe can also control the shade of the cement so this control lead to betteresthetic.

Sometime opaque cement is necessary so that can cover any staining(results from drugs or flourosis) in teeth after we prepare them sooptions are available.

We also have what's called try-in cements, you put a temporary shadefor some time to see how it looks like then you can easily remove it andput a different shade.

Manipulation:

Depends on the type of cements some cement sometimes you need tomix the powder completely with the liquid immediately for 30 or 40seconds, some cement you need divide the powder into for 4 or 6portion and gradually mixed with the liquid, some cement need to mix

90% of the powder with the liquid, so it depend on the type of cement.

4|P a g e


5/13

In term of removal excess some cement need to remove excessimmediately before the material set like zinc phosphate cement. GIC forexample you need to wait until the material initially sets becomes

rubbery or slightly rubbery (your initial generation) and then you canremove excess otherwise if you wait it become very hard and difficult toremove -again depend on the type of cement- so you need always tofollow manufacturer instruction.

You need to see if sometimes we need to do you work gradually forexample you have to prepare 3 or 4 crowns, if you mix the cement all atonce and you want to start to put the crown in the teeth, the cement in

the mixing that may start to set before you finish so you need to mixgradual. Each crown at the time.

So sometime if your work needs some time like you need to temporariesor place a temporal filling for several teeth at the same time or severalcrown need cementation at the same time, you should not mix the allamount of cement at the same time because as soon as you reach to

the last tooth the cement start to set you not be able to manipulate.

In cases that you have difficulty in isolation, when you are using cementthat are technique sensitive like resin, maybe GIC is a better choice soyou have to take that in consideration. Area that can not make goodisolation there is more saliva maybe can not use resin cement becauseresin cement needs area contains NO moisture, but GIC may toleratemoisture than resin. So it depends on the case that you have.

As I said removal of excess depends on the type of the cement, someneed to remove when they are rubbery (when they initially set) someneeds to be removed immediately, you need to use a floss between theteeth to remove any excess, so not just make palatally or lingually youalso need to remove the excess cement between the teeth so you use

dental floss for example.

ZINC OXIDE EUGENOL

5|P a g e


6/13

We talked about zinc oxide eugenol many times before, we said itcan be use as the low strength base or a high strength base and itcan used as a temporary material, as a surgical dressing and itcan be use as an impression material. So is it use commonly.

It has many advantages:

1-Easy to use.2-it has a sedative effect on the pulp.

3-easily manipulated.4-widely Varity in uses in dentistry.

Disadvantages:

1-sometimes isn't very strong2-it has high solubility, if it is not reinforced.

So some time zinc oxide are too weak, have high solubility, and youcannot use them under composite "if you use zinc oxide eugenolunder composite you prevent time of setting of composite, compositeit will not set properly if there is zinc oxide eugenol underneath on thecavity", so this is a limitation. What is the alternative? Probably use a

liner or a base under composite what can I use, it is GIC.

Type 1 of zinc oxide eugenol: it's not reinforced, so it slightlyweaker.

Type 2 of zinc oxide eugenol: it is reinforced oxide eugenol,they can incorporated alumina particles, they can modify the liquidby adding an acid called Ethoxybenzoic acid (EBA), they canalso reinforces with acrylic resin so they are several ways to

reinforce to make it stronger, if they reinforced and add certainmaterial to it they call it type 2 zinc oxide eugenolmaterial so ithas a reinforced agent either acid added to liquid or aluminaparticles or acrylic resin all of these can make it stronger.

There are options of cement with no eugenol for people who areirritated, the tissues that are irritated by eugenol.

6|P a g e


7/13

Usually it can be provided as powder and liquid like the temporaryrestoration material, it can be available as baseand catalyst or 2paste system. Again many forms are available.

Properties:

1-So usually the PH is neutral.

2-it has a sedative effect to the pulp.

3-can cause irritation if using eugenol.

4-cannot be placed under composite.

5-strength is moderate depends if it is reinforced or not.

6-retention is mechanical, so you need mechanical retention if youwant to retain it in a cavity just like amalgam.

7-setting of the material is accelerated by moisture and temperature.

Usually type1 is available as paste and paste you mixed them togetheruntil you get one homogenous color. Type2 is powder and liquid you

incorporate a powder immediately, powder should be incorporated.

Why do we need to know these things?

In your clinic you may not have a dental assistant at some time, youneed to do a mixing yourself so you have to know these thingIf you don't mixing probably you won't have a good properties of thecement when it sets, so mixing 30 second or follow the "manufacturerinstruction ", and then you can increase the amount of powder a little bitif you want to be more viscous "for example" or if you want it to set

faster. So powder is incorporated with the liquid until you get one mix, itwill be like putty.

)pictures in slides 34 &35(

Now this is the paste and paste system, mix them together until you getone homogenous color. If you remember when there is zinc oxideeugenol impression material is available as white paste and brown paste

eugenol same thing here.

7|P a g e


8/13

Zinc Phosphate

Another type of cement is called zinc phosphate; it is made up easilyby mixing zinc oxide powder with phosphoric acid.

Q : where do you know phosphoric acid from ? Where do you used?An : acid etching.

So this cement was very popular, it was used very commonlyespecially for cementing crown.

The problem of this cement is, when it sets the reaction isexothermic, it releases heat and it is initially acidic, so it may it causeirritation, which is why most commonly GIC is used. It is less irritantthan zinc phosphate, but it is a very popular cement when it set it isvery strong, so the setting takes 5-9 minutes which is usually less

than that , and the reaction is exothermic.

Q : How do you reduce this heat that is produce?An : by mixing the cement gradually, dividing it into portion usually 4

to 6 portions and gradually incorporated into the liquid.

Properties:

1-Soinitially the PH is acidic and then become neutral after 48 hours"for GIC it need 24 hours , so less time"

2-Now retained again mechanically, so how do they induce thisretention?

By making that inside of the crown rough "for example" to assist inmicromechanical retention, so when they make the surface rough thiswill help micromechanical retention.

3-When it sets it has low solubility.

4-Usually it sets quickly other than other cements.

5-And moisture is not good, it needs to be moisture free.

8|P a g e


9/13

So gradually incorporated into the liquid and mixing takes awhile like 1or 2 minute, because you need to gradually incorporate the powder,every 15 second you incorporate another amount of powder until you

mix all the powder.

Zinc polycarboxylate

Another type of cement that is like a cosine to GIC is zincpolycarboxylate cement.

The powder is zinc oxide.

Liquid is poly acrylic acid.

So it can be use as a base, can also be use for cementation as luttingcement.

Properties:

1-Now it has lower strength compared to other cements.

2-The acidity is mild.

3-Higher viscosity, that is why not commonly used for cementation,we need cement has low viscosity for cementation; it is better.

4-Retention is chemical and mechanical, chemical; because wehave poly acrylic acid so some ion exchange can happen like GIC

Usually 90% of the powder mixed and then remaining 10 % you can addthem just to adjust the viscosity of the cement if you want it slightlyhigher you incorporate 10% if not don't add it, so it depend on what Iwant to use it, as a base or a cementing agent. This is what terms wehow the viscous I want to the material so how much powder I need toadd.

9|P a g e


10/13

Glass ionomer cements

We learned about GIC so I won't explain the reaction and composition

again, now the uses of GIC:

1-It can be use for core build up "we learned that before."

2-We can use it as fissure sealant.

3-Restorative material especially in area that not subjected tostress.

4-Lutting cement, we can used as a base under amalgam, undercomposite.

Q: How is it manipulated?An: it depends, some are powderliquid system you mixed them, someof them are capsulated, and some of them you need to mix powder with

distilled water.

)Slide 42(

This is Fuji 1 from a Japanese company it is use as a lutting cement, it'savailable as a capsule it is very easy to use, you mix the capsule in theamalgamator "which used in the lab". And then you put it in this device,which is called a gun, and we squeeze the cement out into your crown

and cement it, it is very easy to use.

Resin Modified - GIC

Modification of GIC, can be used for: 1-permanent cementation as liners.2-bonding of orthodontic brackets "orthodontic bands."

Properties:1-can release fluoride.

2-low solubility.

3-PH increases quickly. 4-slightly better properties than conventional GIC.

10|P a g e


11/13

5-The problem with this cement, it absorb some water after it setsthat is why if you got a crown made completely of ceramic orporcelain it is better not to use it, because if this cement absorbs

water it will cause expansion and can crack the ceramic crown.

So under full ceramic crown it is not indicated resin modified GIC, it isbetter to use resin "for example"; because absorption ofwater is less.Again it's available as powder liquid orcapsule

)Slide 44(

This is an example on GIC that is used as a liner , it is very popular &you'll use it in the clinic and in the 4th and 5th year insha'allh

Resin Based-cement

There are similar to composite resin but usually the filler content isdifferent, they usually have lower fillers content.

They have multiple uses:

1-can use to make temporary crowns.

2-can be use for cementation.

3-orthodontic bands or brackets or crown or veneers.

They can set eitherchemically, light cure, dual cure "similar to

composite filling material". Usually resin cement is made of microfill ormicrohybrid that mean the particle size is small.

Properties:

1-they have low solubility.

2-good bond strength.

3-good esthetic; because they are variable in many shades.

11|P a g e


12/13

4-they can bond by etching and bonding " as we said before."

5-Some new product adhesive are (all in on), again they are usedwhen there is no need for etching or priming, they are all in thesame bottle. Some research says that (2 paste system) is better

than all in one.

)Slide 48(

This is a capsulated cement you place it (squeezed) inside the (pulp orgun) sorry didn't hear it !!! and then you cement it. This is excessivecement, always there is should be excess cement coming out all aroundthe crown, so you need to remove excess labially, palatally, and inbetween the teeth; it can be very annoying to the patient and damaging

to the pulp if you don't remove the cement between the teeth.

Compomer Cement

Are also available, they need bonding agent so that you can bond it.they can release some fluoride ,low solubility. So it's acid modifiedcomposite they added carboxylic acid to the material and fluorosilicate

glass.

Manipulation

Depends on the type of cement, it needs to be incorporated totally orgradually some are powder and liquid some are capsulated some of

them light cure, chemically cure.

Sometimes you need to use cement when you repair porcelain crownfor example you need to take the proper shade as I talked in resin" we

said before different shade are available."

This cement is not only used for crown it can used in

12|P a g e


13/13

orthodontics

Root Canal Treatment

When we do the filling we need to place cement to close any gaps insidethe root canal seals, differ type of cement can be used zinc oxideeugenol ,GIC or Ca hydroxide ..but this is another use of cement so they

modified the material slightly to provide different use.

The End.

Done by: Haya Qudah

o

Special thank to my friends Ayah Tareef &Duaa Abu Hmaid for helping me in this script.

Thanks a lot girls

o

, ,

13|P a g e

Documents

Lecture 10, Dental Cements II (Script)