cons sheet # 1 - Yazzan Al--Masri

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cons sheet # 1 - Yazzan Al--Masri

Post by Shadi Jarrar on 16/2/2011, 10:54 pm

بسم الله الرحمن الرحيم

تحذير : يحتوي هذا الشيت على صور
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cons 1.docx
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Composite Restorations Placement
Dr.Suzan 7attar
1st lecture , 2nd semester
Done by: Yazan Al Masri

Last lecture we talk about the composite as a material. We talk about properties of composite (polymerization shrinkage…ect). Today we will talk about how we can do a composite restoration.
In general, composite restoration have specific steps to follow:
1- Acid etching .
2- Bonding agent.
3- Composite restoration.
Composite restorations placement is a very sensitive technique, even more sensitive than the amalgam restorations.
You should always use a matrix band with composite.
There is different types of matrix band used, for example in class V composite restorations we use a matrix band called cervical matrix and in class III and class IV composite restorations we use a matrix band called mylar strip (very flexible and transparent matrix band).
Clinical techniques for making composite restorations are:
1-Local Anesthesia.
2-Tooth Cleaning: to remove any stains, so we can choose the proper shade. Usually using brush and pumice( it is a paste resembles in its composition the tooth paste). Try that the pumice used in cleaning the tooth not to be reach in fluoride because it can interfere with the acid etching step.

pumice
3-Shade Selection: After cleaning the tooth, and before we start the cavity preparation, because once you start drilling in the tooth, this cause dehydration and change in the color. (remember that the tooth is not a single color).
For example, if we have a class V cavity, we can not use just one shade, you should divide your tooth into areas (cervicaly always the saturation of the color is high, more yellowish than the incisal area which is more translucent).
Always use natural light while selecting the shade.
Every composite kit has a shade guide.

Usually we put the shade tape (guide) adjacent to the tooth you want to restore, (under the lip to mimic the real environment of the oral cavity), and choose as quick as possible (30sec.). Don’t take your time in choosing the shade to prevent eyes adaptation. If you can not choose, rest your eyes for few seconds on a natural color or blue color, than, go again and try to choose as quick as possible.

Sometime, you mix two colors together.
Sometime, when you find that the selection using the shade guide is defficult, take a small amount of the shade that you selected and put it in your cavity, then, make curing, if you don’t like it, remove it using the probe (it is easy to be removed because no acid etching no bonding agent are applied).
In composite restoration, we don’t need to ask the patient about his opinion during shade selection, we can ask him in the case of multiple crowns of the anterior teeth.
4-Occlusal Assessment: You have to know where the contact points are using an articulating paper, so you can preserve what we have before.
5-Isolation: It is an important thing for amalgam restoration, but it is more important for composite restoration. Contamination either with water, saliva or even with blood is the enemy of composite, because any contamination interfere with the mechanical properties of the composite.
Isolation may achieved by the using of the rubber dam, clump, wedge (to support the rubber dam, depress the tissues and papilla and expose the cavity),and the retraction cord (which is used to displace the free gingiva, expose the cavity especially when we have a class V composite restoration and to prevent any fluid to enter the cavity).

Multiple isolation using the rubber dam

Isolation using the retraction cord
Restorative procedures:
1- matrix placement: The first thing you do. Why we put the matrix first? Because there is a big risk of contamination, once you put the matrix band around the tooth, it will enter the sulcus and during this it may cause bleeding of the gingival.
So we put it first, put the wedges, then we start our procedures. Matrix band can help also in isolation, it prevent any fluid to contact with you cavity.
For posterior teeth, we use a more rigid matrix, while in anterior teeth we use a more flexible and transparent one.
Again, put the matrix band (whatever the type of the matrix band) before starting any procedures.
Remember the importance of the matrix band:
• It confines the material to the cavity.
• It helps you to develop an axial wall, contour and contact.
• It helps in isolation.
• It limits the excess of material.
The matrix should extend beyond the gingival margin and above the marginal ridge.
Remember the importance of the wedge:
• It prevents the overhang (excess restoration on the gingival margin)
• It makes separation between the teeth to make the proximal contact so it counter balance the thickness of the matrix band, because if we put our matrix without wedge, and put our restoration then er remove the matrix, the space of the matrix band remains as it is.
• It holds the matrix in place.
Where we put the wedge? Below the gingival margin.
2- Acid Etching: why we do acid etching before we put the composite restoration ?
To create what we call micro-undercuts (very rough surface)  increase the surface area  increase the surface free energy (easier wetability and more capacity adhesion).
The micro-undercuts allow the bonding agent to enter. A bonding agent is a composite without filler. We already know that composite is composed of matrix resin and filler. So chemically they are almost the same and they bond with each other. And if we try to insert the composite (which is very viscous) into such micro-undercuts without using the bonding agent it won’t enter very well.
Once we cure the bonding agent, it polymerize and interlock with the tooth surface and provides micro-mechanical retention (for amalgam, it is a mechanical retention).
Do I acid etched the enamel or dentine or both ?
In the past, they just acid etched the enamel(1st, 2nd, 3rd generation of bonding agents), but nowadays, we do what we call total etching (etching both enamel and dentine) but we etched the dentine for a lower period of time than the enamel because the dentine is a vital tooth structure.
So bonding agent and the composite will interlock in both of them (enamel + dentine), but remember always the strength of the bonding agent or the composite with the enamel is much stronger than dentine.
Etching of the enamel affects both the enamel prisms ends and enamel prisms head (not just one area).
Again, acid etching transforms the smooth surface to an irregular surface and increases the surface free energy in enamel, but in dentine it decreases the surface free energy.
Hint: we remember what bevel is. Bevel is not only for increasing surface area, but it is a very useful thing during acid etching, if you don’t beveled your cavity you will notice that the micro-porosity (10-30µm) are very shallow when compared with a beveled and you expose the prisms ends, acid etching leads to more deep micro-porosity and of course when the micro-porosity are more deep, the bonding is more better.


Acid etching on dentine:
• Dentine is a vital tissue.
• Dentine consists of collagen fibers and menirals.
• Dentine composed of dentinal tubules, odontoblastic processes surrounding this tubules, there is peritubular dentine and the remaining is intertubular dentine.
• Acid etching on dentine leads to open the dentinal tubules, demineralization of the intertubular dentine and formation of network (organic material, collagen fibers).
• After that the bonding agent enters the dentinal tubules and compose something resin tags and enters in the spaces in the network and compose a layer known as hybrid layer (hybrid means two things and here we means dentine + bonding agent).
• So the basis of the bonding to dentine is the formation of the hybrid layer.
• Hybrid layer: the collagen fibers network of the dentine and within the spaces of this network there is bonding agent.
• Hybrid layer is formed after:
1- Acid etching the dentine.
2- Applying of bonding agent on dentine.

• Importance of acid etching on dentine:
1- Open of dentinal tubules and demineralization of dentine.
2- Removal of smear layer (residual organic and inorganic debris formed during drilling and tooth instrumentation).
Smear layer closes (fills in) the dentinal tubules, decreasing the permeability of dentine and prevents the bonding agent to penetrate through the dentinal tubule.
Demineralization of dentine due to acid etching occurs on specific depth (approximately 7.5µm of superficial dentine). It must not reach the pulp.
Demineralization depends on:
1- The concentration of acid.
2- The type of acid.
3- Contact time between the acid and surface (acid is applied for only 15sec. on dentine).



Acid etching techniques:
We use phosphoric acid (H₃PO₄).
It comes in syringes (with tip or brush) to apply the acid etch on the area we want. Usually it is not transparent so we can know exactly where we applied it.

The best concentration of (H₃PO₄) found to be between 32%-37% . Less concentration will produce a precipitate on the tooth hard to be removed. Higher concentration will dissolve less calcium and result in poor etching pattern.
It is found in two forms: liquid or gel.
The gel form is better than the liquid form. We can use the liquid form in the case of a large cavity, but the gel form still better in all cases.
Liquid form can spread in all direction and it may cause in sometime irritation to the surrounding soft tissues, but the gel form stays in place.
It’s not a problem if the acid reached the neighboring tooth because after 24 hours in the saliva, the tooth will undergo remineralization.

We apply the acid 0.5-1 mm beyond the bevel and make sure that it covered the whole cavo-surface margin.

We use the acid on both enamel and dentine, the difference is that we need to apply it for more time on enamel than on dentine (30 sec. on enamel) because enamel is more mineralized and dentine is a vital tooth structure (15 sec. only on dentine. Otherwise, dentine may show sensitivity).

In order to do that (30sec. on enamel and 15sec. on dentine) we start putting the acid on enamel margins for 15 sec. then we put it on dentine and wait for another 15 sec. Then we wash it using the same time we used for applying the acid (we wash for 30 seconds in this case).


Wash the acid very good, because remnant acid in the cavity may cause hypersensitivity for the patient and may interfere with the bonding agent.

Now we dry. When we dry the cavity, don’t dry it completely, we need to have same wetness, for dentine, it is important, and we call it wet bonding.

We put the bonding agent on moist dentine. Because if we over dried the surface, collagen network will collapse and the hybrid layer will not be formed. So we can dry enamel as much as we want but dentine should not be over dried.

Dried enamel exhibit a choky frosted appearance.

3- Bonding:
As we said before, bonding agent is a resin, liquid and we apply it on enamel and dentine.
Usually, bonding resin on enamel penetrate into the micro-porosity by capillary action.
Bonding on dentine is more complicated, because dentine is a vital tissue and dynamic structure not easily bonded . adhesion for dentine depends only on the formation of the hybrid layer.
When the bonding resin is applied on the etched dentine, it penetrate the intertubular dentine forming a resin dentine interfusion zone called the hybrid layer.
It also enter into the dentinal tubules and forms the resin tags.
Sometimes, in the old kits of bonding agent, there were an extra bottle (in addition to composite, acid etching and bonding), which is called primer.

The use of primer: Dentine is hydrophobic specially after doing the acid etching, so the bonding agent may not penetrate very well into the dentine. To overcome this problem we use a primer to prepare the surface for receiving the bonding agent. These days, you can find the primer mixed with the bonding agent in the same bottle.


The bonding agent is applied on a cotton pellet, and then you dampen the surface, after that we make a little blowing of air to spread the bonding agent and help it penetrate inside the micro-undercuts. Finally, we make a light cure, because as we said before, it’s a composite without filler so it won’t set by itself. (This is in the case of using light cure bonding agent).

Now how much time do we need for light curing the bonding agent? In general you have to read the instructions given by the manufacturer, but mostly it needs 20 seconds.

We just said that we need 20 seconds for curing the bonding agent, but what about curing the composite? Actually, it needs 40 seconds (for each increment). Keep in mind that you have to cure the composite from all the aspects (labially, lingually…) to make sure that all monomers are polymerized.

If contamination happened at this stage, we have to repeat from the acid etching step.

4- Composite Insertion:
Using a plastic instrument


5- Finishing and Contouring:
If we found a little bit excess on the labial margin for example, we can use a finishing bur to remove it. In the end we use finishing disks to give it a very nice luster.
We usually use fine diamond finishing burs or carbide burs.
Finishing disks has many different shapes. For example, the flat ones are used for facial or inter-proximal aspects.

If you want it to be shinier, you can use the same pumice that we used before.

Try to make the occlusal morphology before curing the composite. And you can modify it after curing by using the burs.


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Shadi Jarrar
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عدد المساهمات : 997
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تاريخ التسجيل : 2009-08-28
العمر : 26
الموقع : Amman-Jordan

http://jude.my-rpg.com

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