cons sheet # 9 - Lana Obaidat

بسم الله الرحمن الرحيم

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http://www.freefileconvert.com/converted/4cf0252d3c15c/Matrices.doc
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Matrices
The difference between class I and class II :
Class I is on the occlusal surface so it’s confined ( meaning you only have one way to get access to that surface directly) unlike class II where you can’t get direct access to it because it’s on proximal surfaces for posterior teeth

Types of restorative materials that we use are either:
1) Indirect restorative material : those should be done at the laboratory
2) Direct restorative material ( plastic fillings ) : those we do them directly in the patients’ mouth
We call them plastic materials because they undergo plastic deformation (they don’t get back to their prior shape) , (if you mix amalgam at first it’s shape is like a ball then after compressing it , it will look like the shape of the cavity that you want to fill) so at the point when the material gets the same shape as the cavity we call it plastic deformation , keep in mind that the material hadn’t set completely.

Same with composite, we apply it to the tooth and then shape it to the form that we want and after that we light cure it

Going back to class I: in amalgam restoration we can compress or condense the amalgam inside the cavity easily because there are walls surrounding it from each side, But in class II (since we don’t have walls to give support because the cavity is extended to the proximal surface) if we condense the amalgam on the occlusal surface there will be no walls to support it while it’s setting.
if we’re talking about a material that has already set before applying it there will be no problem because the material has hardened and became like metal ( amalgam is metal alloy) but since that we’re applying the material before it is completely set it will definitely raise an issue.
<<<< The Dr. asked how much is the CFS of Streptococcus Mutans for a patient to be in a high risk of getting caries? the answer is 2.5*105 Colony forming unit YOU ARE NOT required to know this right now because it’s a question for 4th year dental students ^^ but it was mentioned >>>>
Amalgam is set in phases : γ1 and γ2 ( you should know the phases and which is the weakest phase (gamma 2) -- please revise them from the dental material course )
Matrix bands will provide the support needed in the setting phase.
after the setting phase you will remove the matrix band ( the patient cannot leave the clinic while still wearing it)

Matrix bands in details:
Matrix bands are needed in:
Class II amalgam restoration
Class III
Class V
Class IV >> for contact points
In general in restoring any proximal surface we need support .
And most importantly it’s needed for class I with lingual and buccal extension

The ideal fetures needed for the matrix band:
1) Re-establish contour (proximal contour : it is the same as walls or margins)
We need to re-establish the contour so that we won’t have an overhang also so that there will be no space left between the filling and the line angle of the tooth structure itself.
between the walls of two adjacent central incisors the most important thing to know that there’s a contact point ( or any two adjacent teeth )

we need to re-establish a positive contact point because :

a. Esthetics: so they won’t have diastema

b. Function: to prevent food accumulation between teeth (let’s pretend that you’re going out for a gathering on manasef x) if you don’t have the proper contact point meat will get stuck between your teeth and it’s unacceptable for a dentist (or anyone really) to insert his hand between his teeth and try to pick it out :/ anyway the main point is that it prevents food accumulation there.

The importance of flossing is to prevent food from getting stuck between teeth (anyone who flosses knows that there’s some resistance while they’re inserting the dental floss between their teeth)
Mesial drifting due to a loss of even one tooth will cause mal-occlusion which in this case we will fear from the interferences ( 98% patients won’t have the right centric relation ) and that will cause various issues.

* the contact point should be a positive one *

• A study was made on some dental students, they all needed class II amalgam restorations; one on the right lower 6 and another on the left lower 6 , they made it for them but on one side the didn’t use a matrix band so there was an overhang in the amalgam , so some amalgam reached the gingival sulcus because of that , after two days they all suffered form bleeding , discoloration of the gingiva and they started to have periodontits ( bone loss).
In amalgam and composite restorations most failure is due to the lack of adequate seal of the marginal ridges and this is called secondary failure.

2) We also need to allow an adequate bulk of the material in the cavity to overcome the resistance force in the amalgam
The matrix band should be as thin as possible to re-establish the contour ( because if it was thick and we removed it after using it there will be a space )
3) It should be smooth : because rough surfaces will cause plaque accumulation
4) It should be withdrawn easily
5) Easy to place
6) They can be used with all restorative materials

Tofflemire matrix retainer :


it’s made out of: a slot : were we insert the band itself in it and it’s used to hold it in position
A band : has a specific shape < square or semi-circle >
(Please refer to the slides to know it’s shape , and how it surrounds the tooth)

The retainer should be placed on the buccal side, the open side of it should be placed towards the gingiva

Wedges ( 2 in number) : they are used to separate the teeth so that we’ll be able to insert the matrix band , and when we remove them there will be an elastic recoil between the adjacent two teeth to close that area

After the material has set, a part of the marginal ridge is carved before the removal of the matrix band because we do not relay on the matrix band to make the outer marginal ridge formation and this is done by a probe

To remove the tofflemire retainer we stabilize it from both sides by both hands then we unscrew the outer half, and then we remove the retainer, after that we slide the matrix band out from each side, you should know that if you try to remove it as one piece then you’ll end up by breaking one of the marginal ridges most of the time, after that you should remove the wedges.
• Tofflemire matrix band is also called circumferential matrix band because it surrounds the whole tooth
Ivory retainer :

the main purpose of this retainer is to cover only one side of the tooth (either mesial or distal side)
we can’t use a tofflemire retainer when:
1) the adjacent teeth ( the one you’re treating and the one next to it) have very heavy contact
2) if you have a patient aged 11 years and his lower 2nd molar is partially irrupted here we can’t use a tofflemire so an ivory retainer is used instead


Automatrix system: it’s available in different sizes and you use it for one time only
The different sizes :
1) Narrow regular: used for premolars
2) Medium thin: used for molars but this is mostly used for composite
3) Medium regular : used for small molars
4) Medium wide: used for very big molars

• Matrix retainers have a knob and we use a screw driver to tighten it

Posteriors proximal composites :
We all know that amalgam can be condensed by pushing it inside the cavity mesially or distally but composite is a really plastic material so you need to put it with an artistic movement to get the shape you want, in anterior teeth that isn’t much of a problem, but in posterior teeth until now there’s no way of packing it in a good manner
Composite had many problems like polymerization shrinkage and tooth wear those have been solved by nano-technology techniques
SECTIONAL MATRICES : it’s an easier way to solve the problem of creating optimal contact area in posterior teeth with composite restorations
Composite needs wedges more than other material and those wedges should be bigger so that the teeth will tighten even more (pre-wedging) also reflective wedging is even better.
• PALODENT SECTIONAL MATRIX : please read about it from this link http://www.dentsplymea.com/products/restoratives/palodent.html

Weak matrix bands can’t be used in posterior teeth so they are more used in anterior teeth


TYPES of matrix bands :
Triodent V3 ring system: it will provide high pressure on premolars and pushes it out of the way, this matrix band is shaped in an anatomic form of the tooth, they are more expensive than the usual matrix band

The gold standard of posterior matrix band is the V3 Rings , Palodent, Composi-Tight sectional matrix
• About the Composi-Tight sectional matrix : the most important thing about them is the rings because they make the separation between teeth also it’s matrix bands come in uniform shapes

Tofflemire bands are made from very soft metals and they can be shaped into the desired shape, they can be used instead of the other bands and they are much more cheaper than other types of bands

Retainer-less matrix band : two types are mentioned here : 1) Super-mat system 2) Omni matrices

Contact forming instruments:
1) Belvedere : it’s a tongue cap form instrument , it’s really expensive because it’s gold plated and it is conical in shape
2) Light cure tips : after you have filled the cavity with composite you’ll have to put the tip of the light cure on the gingival margin after that you’ll add another layer and that way you’ll get a fully light cured composite
Problems with Composites:
1) It’s Hard to reach a positive contact
2) It’s Hard to maintain a positive contact : we lose the positive contact because composite can wear off easily since it has low hardness
(Unlike the amalgam that has high hardness)
Composite will lose its positive contact within 6 months of placement

Pre contoured, pre wedged metallic sectional matrices are better in forming tight contacts than plastic/clear matrices.


The End
Done by: Lana Obeidat
Cons. Lec. 1st one after the eid

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