Lecture 20, Preventive dental materials (Script)

8/3/2019 Lecture 20, Preventive dental materials (Script)

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Preventive dental materials

Dental material II

lecture # 20

Slide 2

Today we will talk about preventive dental material so in general

preventive materials are used to prevent injuries or disease

Three classes of materials are involved:*Fluoride gel that are used to protect against caries because

fluoride can kill bacteria and induce remineralization of enamel and

dentine so it protect from carious attack.

*Pit and fissure sealants: used to protect against pit and fissure

caries so that tooth surfaces can easily clean by tooth brushing (no

food accumulation, no initiation of caries.(

*Mouth protectors or mouth guards: used to protect teeth from

forces like boxing.

Slide 3

Fluoride in general can be available in the form of mouth wash, gel,

or varnishes:

*mouth wash or rinses like Duraphat rinse (Colgate(

*varnishes that applied by a dentist using a brush to minimize

food sensitivity by blocking dentinal tubules and preventing

irritation of pulp.

*gel which is made from acidulated sodium fluoride contain 2%

sodium fluoride with 1.22 1.32 % fluoride ion ( stannous

fluoride maybe used too. (


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Now these products can be slightly acidic like acidulated

sodium fluoride or neutral (PH 6-8) to prevent acid etching of

restoration like composite or to prevent sensitivity so you

select the one which is more appropriate for your patient.

Slide 5

When we use these products?*

It depend on many factors especially oral hygiene and caries

risk of the patient so if you got multiple carious lesions or high

carious risk patient it might be good idea to use fluoride every

three month , if the patient is normal we use fluoride once a

year.

So these fluoride applications use to protect against smooth

surface caries (lingual, buccal, distal, mesial or root caries(

Smooth surfaces are protected by fluoride application* .

*Pit and fissures are protected by pit and fissure sealants.

*How much protection does it provide?

It depends on frequency, duration and method of application.

Now if we use a gel it should be viscous enough so it can be handledeasily and it should be flowable enough to flow all around teeth (not

too viscous, not too flowable.(

Slide 6

The gel is provided in a paste, put it in prefabricated disposable tray

(upper and lower trays are attached to each other) then they are

placed at the same time for upper and lower teeth for 4 minute


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without rinsing until 30 minute to get enough time for fluoride to

penetrate tooth surfaces.

Slide 7

Pit and fissure sealants (resin or GIC based materials.(

Pits and fissures are enamel faults whish are inaccessible to

cleaning using tooth brushes so food and bacteria can be easily

accumulated inside these faults

How can we treat this problem?*

By using pit and fissure sealants to seal enamel faults so it can beeasily cleaned.

Now different product of pit and fissure sealants can be used for

example Heliosealwhich is resin based sealant but with fluoride

added to it (slide 9) to improve its prosperities and allow chemical

protections (releasing fluoride) in addition to its original mechanical

protection (sealing.(

Another example is conseal F but it's without fluoride.

Slide 8

Resin pit and fissure sealants are similar in composition to resin

composite put more flowable (less filler ) and it provide

micromechanical retention so acid etching is required.

As we said pit and fissure sealants are similar in composition to resin

composite so it consist of:

*Bis-GMA

*UDMA

Also it may have small amount of filler to add strength so it will

remain in its position for a long period of time or it may have no filler

but it less preferable.


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If we lose the pit and fissure sealants, its protection will be

lost thats why we need to review the patient to make sure

it still there otherwise we need to repeat it again.

Children need pit and fissure sealants more than adults

because they dont apply good oral hygiene.

so again pit and fissure sealants have physical and mechanical

prosperities according to its composition , resin pit and fissure

sealants have a good mechanical retention compared to GIC pit and

fissure sealants because GIC are weaker and dont bond strongly to

the tooth surfaces.

Acid etching used when applying resin pit and fissure sealants to

*clean the surfaces

*improve wettability

*create a rough surface

)The same reasons when used in composite.(

Slide 11

Sealant penetration maybe difficult due to:

*air entrapment

*food debris accumulation

To overcome this problem we apply abrasive paste (????) to remove

all food debris before applying acid etching and sealants.

*How far the resin penetrates?

It depends on the material itself***:


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*surface tension of the material: the lower the surfaces tension the

more it can flow and penetrate the surfaces

*viscosity of sealant: the more flowable the material the more it

penetrates the surfaces

*contact angle of sealant with enamel

***shape of fissure: long narrow fissure is more difficult to penetrate

compared to short wide fissure.

Done by : Reem Alebbini

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Now when a sealant is not used??

1.If the molars are caries free for many years.. We don't use a sealant..

oral hygiene is good enough.

2.If the patient uncooperative because to use a sealant you need acid

etching and bonding and application of the sealant.. You need good

moisture control.. And after that you need good oral hygiene.. So if the

patient can't cooperate with you, can't maintain good moisture control

during the application of the sealant and if the oral hygiene is very bad

then why do this?? Why waste money and time?? (You can't do it(

3.If there are no pits and fissures or if the pits and fissures are too

shallow they can cleaned easily with the tooth brush.. No need to use

pits and fissure sealant.

4.In some cases we cant apply the sealant immediately even if the 6

molar erupt when we dont have a proper isolation to the tooth from saliva;

so here we use GIC coz its less sensitive to moisture contamination.

So these are the reasons why we dont seal.


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NOW, how do you apply the sealant?

Sometimes disposable tip is attached to the syringe then you apply it oryou can use a brush. The important thing is to cover the whole area, to

cover all pits and fissures. So make sure that they are close up, and then

you light cured.

Most of the product now is light cure, so no need for mixing.

If you remember in addition to pit and fissure sealant we can use flowable

composite, it is flowable enough to be used, so we acid etched then we

apply the material and light cure it.

Some time a small sponge may be used, it doesnt matter what method you

used as long as we cover all necessary areas, and these areas have to beetched previously if any part of the tooth or any pits and fissures were

not included in the etching they will not be able to retain the sealant, the

sealant will be easily removed.

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Now the third topic in this lecture is mouth protectors

)Mouth guards:(

These devices are generally made from polymers.

-how are they formed?

Some of them are already prefabricated

and some of them are costume made, you


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make an impression and the lab conduct the device for you, so the

materials that are used to make them are thermoplastic materials which

mean that when you heat them they become flexible and then you can

form them according to the patient dentition and then they can be givento the patient, they can be used to protect against injury.

They can be form like this..

These are custom made.

Also it can be used as a tray usually to apply a bleaching agent.

And it can be used to apply fluoride gel, you place the fluoride gel and

then inside it and ask the patient to wear, or for protection.

So as a summary, we use mouth protectors to:

1.To apply bleaching agent.

2.To apply fluoride gel

3.Forprotection.

Types of mouth protector:

1====so they can be stock made or (prefabricated), they do not fit

very will and usually they lead to some discomfort because the fit is not

good.. they are general in size and usually they have bad taste and odor.

2====some of them are mouth formed, so the material come as sheet..

the patient put it in warm water and then place it in their mouth and try

to adapt it, the fit might be better but still not perfect.

3====the best one is custom trays, you take an impression, in the lab

they pour it in to a mould, and on top of this mould they place the material


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and shape it properly, remove excess so it will adapt very well for that

specific patient.

So always custom made is better because:

1.Better comfort, because they fit exactly in the patients mouth & had

the exact shape of the teeth or arch.

2.No irritation or minimal irritation.

3.No bad taste or odor.

4.More durable.But the problem is it's more expensive.

Now composition:

Several materials can be used to make these, the most commonly use one

is Thermoplastic polymer (poly-vinyl acetate-polyethylene polymer) or

called ethylene vinyl acetate (EVA) this is the 1st one.

2.polyurethane3.vinyl plastisol

4.rubber latex

Nom according to EVA, usually they come in the form of sheet (1.6 to 3

mm in thickness), they have to be thick enough so that the patient will not

bites through them and perforate them, and in the same time they wont

to be toothache in order to not to lead discomfort to the patient.

So the 1st material which is EVA, the properties of this material before

and after the insertion in the patient mouth are different.

Once the material is made (like a night guard), and place it inside the

patient mouth, because there is moisture, because there is temperature

Material properties will slightly change, they will have more flexibility

because they have higher temperature and moisture inside the patient


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mouth, and they have better impact strength, but there tensile strength

will be less.

The main idea here is that, the material the way it behaves under stress

become different, because inside the patient mouth the environment isdifferent.

Now,polyurethaneshave better strength but they need highertemperature during processing, which mean they are more difficultto process.

Other materials like rubber latexandplastisol, their strength and

hardness is lower and they are even more difficult to process, theyneed more expensive machines.

SO,the best choice is EVA.

Usually when the patients wear this guard, they complain mainly of:

1.Soreness in the muscle.

2.Irritation.3.Discomfort.

4.Gagging.

Now if the mouth guard is made correctly, this mean that there is no

complained as such.

So it take some time for the patient to get used to the appliance , but

then after sometime if it's made correctly it will not caused any problem.

Now if it's made too thick, it will be stronger but it will cause more

discomfort, usually final thickness especially in area of high occlusion

should be 4 mm.

)y3ne usually 2 sheets are applied on top of each other so that the final

thickness is 4 mm over cusps and incisal edge "the areas where there is

high occlusion"), and also to compensate for shrinkage because thematerial firstly is soft and flexible to shape it in the model and then it


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will cool down, when it cools down it might shrink in a little bit that's why

they need to add excess to compensate for any shrinkage, so that when

you place it in the patient's mouth.. It will be thick; they will be no

deficiency in any area.

Now this is an example of failure in these material,

the material was either weak or it's too thin, so the

patient will biting through it it's specially a problem

with patient who clench on their teeth (bruxisim.(

Previously they use to make soft night guards (flexible material).. Now thenewer one will be hard material.. If they are harder, they will provide

protection for a longer period of time.

So, if the patient have para-functional habit that is not a normal one ,

occlusal load will be more and then there is more chance of failure or

tearing or biting through the device and this will affect how long the

device is going to remain functional.

Now if the patient also does not maintain the device or appliance

correctly, it will also be damage, so we also tell the patient to after taking

off the device to place it in the mold (stone mold) and place it in a rigid

container to protect it from deformation.

Custom made:In general we need to take an impression usually with alginate, the

impression is poured into a model, and then 3 methods are used to shapethe thermoplastic material:

1.By hand.. warming the thermoplastic sheet and then adapt it in the

model by hand but this is not very accurate.

2.Pressure lamination

3.Vacuum

)The palatal area will not be included(


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So these 2 devices can be used (pressure lamination & vaccum) , so what

happen is the machine contain the sheet of the thermoplastic material, it

moves lower and lower until it come in contact with the model, the

material is softened so as soon as it comes in contact with the modeleither by have a pressure from the machine it will adapt the sheet on the

model or by using vaccum, the vaccum will suck the material on top of the

model and this also will cause adaptation of the

sheet on top of the model.

So these methods using vaccum or pressure

lamination provide much better adaptation of the

material on top of the model because this is done under force.

Now once adaptation occur, another layer may be added and then we allow

it to cool down and excess can be removed, so the night guard will not over

extended into the buccal sulcus and into the frenum.

Now, if this is done for a patient that has a mixed dentition y3ni

primary and permanent teeth for example:

-He has a permanent tooth that not erupt yet.. (The D or E is extracted,

still the 5 or 4 dont erupt yet, a space can be provided under the mouth

protector so if the tooth comes to erupt it will be enough space to it.(

How this space is provided??

By placing for example a piece of cotton on the model where the

permanent tooth might erupt so that when a sheet is adapted it will not

directly contact the model, there will be some space underneath it.


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As I said, trimming is done later on, so that there will be clearance for

the frenum, it will not directly contact the buccal sulcus, and it will not

cause irritation or injury or ulceration of the tissue.

Any edges should be smoothens, a flame may be used to soften the edgesand then you can actually with your figures make them rounded so that

they are not sharp.

Now, for occlusal adjustment usually we heat the surface of the appliance

and we ask the patient to bite in occlusion, any high spot can be removed

because they should be contact all around, it should not interfere with the

occlusion.

Hll2,in some cases we need to increase the vertical dimension of the

patient mouth so extra sheet of the material should be added .. So that

we rise the bite.

When dose that happen???

If the teeth suffer from attrition, if cusps are flat, this mean that

the vertical dimension in the patient is loss or becomes less.. Which can

be harmful to the TMJ and muscles.

So if the vertical dimension of the patient becomes less due to tooth wear

it can be brought back to original position by using extra thickness of the

night guards, place it in the patient mouth so that we bring the muscle and

TMJ to its original position and then restorations can be placed on top of

teeth.

Now, how is it maintained??1.It should be placed in a rigid container.

2.It should be cleaned.

3.No abrasive should be used.

4.Maintain a good oral hygiene.

The end


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Done by: Samar Al omari

Foregive me if there is any mistake

Good luck to all =DSpecial hi goes to my sis kakkoooosh a7la 9adee8a

bkooooooooooool el denia

Luv u ya 7ob

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Lecture 20, Preventive dental materials (Script)