DM Sheet #14 (last lec) By Nada Kadri

by **Sura** 31/12/2011, 10:58 pm

http://www.mediafire.com/?4va42gdytv968i4

by Ibrahim Abdullghani 1/1/2012, 7:21 pm

the link is not working with me plz can u upload it on another website sad

by Ibrahim Abdullghani 1/1/2012, 7:23 pm

I think there is a problem cuz I tried to download several things but none of them work surprised

by **Sura** 1/1/2012, 10:16 pm

actually the link is work !
but here is another link :)
http://www.mediafire.com/?5403ksn9fccosat

by **Shadi Jarrar** 2/1/2012, 11:04 pm

Development of Dental Materials

29/12/11

Today we will talk about the development of dental materials.

What are nanocomposites?
Filler size is 8-9 nm. The doctor then started to talk about how it is manufactured in Dentsply company in Germany.
bijeeboo 7jar sawda min il Hind.. these rocks are hard with low brittleness. These rocks are put in a barrel that is connected to a motor that keeps spinning. Inside the barrel are small rocks… the filler is then put in the barrel. The filler we use in composite is silica. Cured pieces of composite can also be put. The barrel continues spinning and spinning allowing the fillers to hit against (ti7tak) the rocks therefore making them smooth like powder. They measured the diameter of these powder-like particles after a certain RPM and a certain period of time. They found that the diameter was 9 nm.
They then used these fillers in composite and measured certain characteristics.

What are the important characteristics that must be measured regarding composite?

1. Shrinkage
they put the materials in tubes and then polymerize it. The difference is measured, you can use Archmides’s equation

2. Working time

3. Depth of Light in curing

Imagine a tube, and at the base there are holes. The base of the tube is transparent. Fill the tube with composite and then cure it. Measure the length at which the composite becomes soft. “ t5ayyal shilin with 3-4 holes kol wa7ad bi depth mo3ayyan bil tube w kollo transparent.. bit3abbeehom composite w bti3mal curing…”

Make sure that you use the same light unit for all holes, and make sure that you use it at the same time as with time the efficiency of the light cure decreases.

4. Wear Resistance

Artificial tooth brush on different composite materials that keeps brushing thecomposite (the bursh is connected to a motor) and then the amount of composite lost is measured

5. Color stability

Using a spectrophotometer… delta E

6. Compressive Strength
min7o6 bi tubes w mnikbisoh w minshoof esh bit6a77an aktar.
il curve bidal yi6la3 w lamma yseer fi failure bos2o6

7. Stickiness
this is something that you may suffer form in your clinics … after filling a cavity w/ composite you take a radiograph and find it to be empty!

Bijeeboo tapered metal rod (like the tip of a pencil) put a nonpolymerized composite block in front of it. w kollo lazim ykoon fixed 3ala tawlat w ilhom rail. You bring the rod closer to the composite until the rod touches the composite. At the moment that the rod touches the composite, you pull the rod away from measure the elongation of the composite. The higher the measurement, the stickier the material.
The condensers you use in the clinic also have stickiness! So the stickiness problem in your clinic comes from both the condenser and the composite… so sometimes you may put the composite in your class 2 composite w il compsite bitla3 ma3ak… you cure without noticing the void! This can also occur in class 1 fillings…

shrinkage can occur in class 1 composite leading to shear on the tooth and thus sensitivity, we can solve this by putting a groove in thecentral fissure and thus relieving the stresses! If the fissure did not solve the problem then replace the filling.

8. Leakage

Age the filling… for example expose the composite model to cyclic loading in artificial saliva (with standardized values… for ex this many cycles in this period of time) OR you can keep alternating them from hot to cold water baths (this is also an example of cyclic loading)
then you measure the leakage using dyes! Cut the composite into cross sections and measure the depth of the leakage of the dye.

Now the doc is gonna talk about the last materials illeh btosta5dam 3inna…

When using self etching composite you must use strong LED light to prevent leakage of acid inside the tubules.

Desired characteristics of new adhesives: good bond strength of enamel and dentine… to get rid of the problem of dentine bonding agents and enamel bonding agents.They must be easy to apply and use. Not get degraded. No post op sensitivity. Universal use (meaning using it on direct and indirect restorations, using it on different manufacturer’s products and using it on both enamel and dentine)

doc then talked about indirect composite restorations… it’s kind of like inlays and onlays and they are polymerized in the lab (after giving the lab an impression).. and then in the clinic all you do is bond. Note that the prepared tooth must be flared… not like with amalgam preparations.

The amount of bonding agent on the tip of the microbrush must be saturated (moshbi3a). (note that the time of application should be quick as it can evaporate from the brush). After putting the bonding agent on the tooth, it should have a glossy appearance. Then dry with air for a few seconds to make sure that the bond enters the tubules and etched surface). If the microbrush is deficient, then the tooth surface will be deficient
Development of Prefabricated Posts

We used to use titanium. Then, zirconium (ZrO2). And the latest is glass fiber.

Why is the latest development glass fiber?
glass fibers are like sho3ayrat shabakit il 3ankaboot. Lamma minlazzi2 il sho3ayrat bi ba3idhom, bidal fi beinat-hom 7arakeh which is similar to dentine. We use them in anterior teeth because they are the most susceptible to bending. In posterior teeth, the amount of bending Is a lot less. Some dentists use it in both, it all depends on the preference of the dentist. However, regarding the bending theory the doc said to keep in mind that the dentine after endo treated has different properties.

What about titanium?
can cause grayish discoloration L… problem in anteriors
with porcelain over it, we can mask the color.. however there are problem areas like the coronal part of the root.. which can lead to problems if gum recession occurs… the root will be exposed and the grayish color will show.

the doc then showed pics of acid etch and sandblasting, the material should be put in alcohol to clean it.. then we put primer on the post. Panavia is the strongest bond in the world, followed by 3MS ishi.. (couldn’t hear it sorry) and followed by Uni- ex (?) but the disadvantage of Panavia is that it has a lot of steps…
Panavia comes in 2 tubes… you mix them together for 30 seconds. And then you apply it on the post ( note that the post already has a primer on it)
Acid etching is better than sandblasting regarding titanium posts. Bs il fiber post ma minseeboh bntlaz2oh bi 6ooloh kamel w ba3dein min2o9oh. You only cut it after taking an xray. Sandblasting leads to entrapment of aluminum oxide particles affecting good bonding and it can initiate cracks in the post.

The doc then mentioned a different bond called Ivoclar which is a big company located in Lichtenstein. ;)

The doc then started talking about resin bonded bridges I think but the slides weren’t in English and frankly I had no idea what was going on but here is what was said… mni3mil surveying w minshoof il undercuts 3ashan ni3mil path of withdrawl.. mna5od index bil putty w minthabbit-ha 3al head w parallel to the long axis of the tooth. And this is about development of the surveyor.

Then the doc showed a pic (the slides were still in another language -this is what the doc said): Kanat il gum shway irregular w mni3mil surgery isimha kleiv (?) technique… we empty the connective tissue under the surface of the pontic w bitseer zai il mghara (cave)… this is called aesthetic dentistry… lazim ti3mil provisional 3ashan ydal darib 3al tissues illeh faddeit ma7alloh w ya3ti il shape ta3 il pontic ridge surface illeh biddak iyyah. Fa 7a66eina il provisional 3ashan y7afiz 3al shikil ba3dein 7adadrna il zirconium ma3 wing.

There were some things in the sheet that were not translated as they weren’t in scientific terminology per se and I thought it would be more accurate if it was just written as it was said.

Last dental materials sheet ever ever and last lecture of the semester J Enjoy people and good luck in finals!

Done by: Nada Kadri

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