cons sheet # 13 - Ibrrahim Sa3adeh

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cons sheet # 13 - Ibrrahim Sa3adeh

Post by Shadi Jarrar on 25/1/2011, 6:26 am

بسم الله الرحمن الرحيم

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http://www.mediafire.com/?5p86a06h1was27f
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Class V cavity preparation

Class V (according to Black’s calcification) occurs at the cervical third (gingival third) of labial, buccal & lingual surfaces of all teeth NOT involving grooves or pits.

So if the caries start on a groove or pit even if it’s found on the cervical third we don’t consider it as class V but we consider it as class I (pits & fissures caries)

So sometimes a carious lesion is formed within the pits that are found at the end of the buccal groove, misleading the dentists to think that it is a class V cavity while in fact it is class I.

As you remember we talked about the origin of caries in each class, for example:
Class I  caries
Class III  mainly caries
Class IV  caries or trauma
Now class V  caries or non carious lesions (abrasion or erosion)


Abrasion lesion


Now about the materials we can use amalgam, glass ionomer but mainly we use composite material especially in anterior teeth because of esthetics.

*Now if put composite on anterior teeth we will not differentiate between it and between the teeth structures but the glass ionomer doesn’t have a high translucency.

We use amalgam in several cases:
1- Non-esthetic areas
2- For isolation in areas that we have difficult moisture control
(Note: the absolute contraindication for composite use is that if we don’t have good isolation like if it’s were sub-gingival so impossible that we will not have a gingival fluid so surely there will be contamination)
3- Limited access and visibility
4- May use in partial dental abutment but we can use composite also in this case
The most important is number 2

Advantages of amalgam:
1- Higher strength
2- Easily manipulated
3- Less sensitive to moisture (it’s wrong to say that amalgam is non sensitive)
4- Cheaper

Disadvantages of amalgam:
1- Not esthetic
2- Not very conservative


Initial clinical procedures of class V:
1- Anesthesia
2- Occlusion assessment:
*Now to describe how occlusion have an effect on class V we will take about something called abfraction (non-carious lesion):
It’s an extra occlusal stress on tooth so the tooth flex at the neck and this flexion is actually too small (micro-flexion) we can’t see it but over years we will have chipping of enamel & dentine in the cervical third.
3- Shade selection


*Mostly you will have class V lesions extended to sub-gingival areas so sometimes you need to expose your area to get a good access & visibility this is done by several ways:
1- Surgical exposure (cutting from the gum)
2- Rubber dam
3- Retraction cord: the retraction cord is inserted gently below the gumline into the gingival sulcus, around the tooth to push the gum tissue away from the margins of the tooth so you will have a good access.

4- Tooth isolation:
• To prevent contamination
• Enhances the asepsis while working
• Facilitate a good access & visibility
Any moisture from saliva or hemorrhage will affect the physical & the esthetic properties of the restoration and the most important thing it will affect the bonding of composite to the tooth structure there will not be any bonding so your restoration is a FAILURE even if it’s beautiful if you touch it with a probe it will break down.
Isolation methods:
• Rubber dam & clamps
• Cotton cords
• Retraction cord: it’s a thick cord make a little displacement of the gum without harming the gingiva and it also make isolation by preventing the gingival fluid to go out to the cavity because the sulcus isn’t a dry area there is always a gingival fluid coming out from the sulcus




Types of class V preparation:
1- Conventional: we make it in different situations:-
*If the preparation is partially or completely on the root surface we don’t have bevel so we have to make it conventional
*Also if we want to make an amalgam class V preparation

Access cavity:
*Class V is very accessible especially if it’s on the buccal surface so we use straight or tapered diamond fissure bur high speed at first and then low speed, we can also use a round diamond bur if the lesions were found adjacent to the neighboring teeth then maintain 90 degrees angle (conventional)
*The initial depth will be 0.75mm inside the external tooth surface
*The axial wall is convex outward and follows the external surface (DEJ) in the crown and if the preparation extended toward the gingiva it will be convex occluso-gingivally too
*The external walls (mesial & distal) are 90 degrees cavosurface margin
*The axial depth provides strength for the preparation walls, strength for your restoration and it allows desmet?? of retentive grooves
*If we look at the tooth from the labial surface we can see the external walls most of the time because they’re divergent especially mesio-distally and the reason is that we are following the external contour and we want 90 degrees so the walls will be divergent outward
*Retention grooves in class V are found axio-gingivally & axio-incisally and you can extended all around if the preparation is very large (axio- “gingival, incisal, mesial & distal”)
*REMEMBER: we prepare the grooves with a quarter bur (round, low speed) in the final cavity preparation step

*These grooves are 0.25mm depth in the DEJ, and 0.2mm away from the DEJ
*Also we can make the grooves with hand instruments like chisel
*The angle of the grooves at an angle that bisect the angle between the external wall & the axial wall
*Sometimes we make coves instead of grooves, it follows the same principle as grooves but they are shorter and made on point angles not on line angles
*We make 4 coves instead of 2 grooves incase if the cavity is very large & very deep and we don’t want to endanger the pulp by exposure so it’s safer to do coves rather than grooves
*Remember that the grooves and the coves shouldn’t remove the dentine immediately supporting the enamel so the initial depth will be 0.5mm instead of 0.2mm inside the DEJ to give yourself a space without undermining the enamel
*Pins are very difficult and we can’t use it with composite so we don’t use them unless we don’t have any other choice

2- Beveled conventional:
*Like the conventional but it has bevel we do it at the final stage
*The location of the bevel depends on the thickness or the presence of the enamel
*The width of the bevel depends on the how much retention we need the more the bevel  surface area ↑  retention ↑
*Indications for beveled conventional:
1- Moderate to large lesions occurring on the crown portion
2- We have enamel
3- Composite will be the restorative material

*In class 5 cavity preparation , beveling is preformed mainly incisally, but it can be found mesially or distally but NEVER gingivally ; as the enamel is critically thin over there therefore the finishing and polishing step will be extremely difficult to perform
*So we use it when the lesion is located in a very deep subgingival area, because in such cases we don’t have an access to the margins so we need to expose these margins
Initial cavity preparation of beveled conventional:
-Hold the bur at 90 degrees angle with the external surface
-The axial wall usually uniform in depth
-The retention established by bonding to enamel & dentine since we are talking about composite
*Beveling is made at an angle = 45 degrees with the external tooth surface
*Since the bevel is made at 45 degrees angle so we can’t use amalgam
*The axial depth is 0.2mm inside the dentine unless we want to put grooves so we increase it to 0.5mm inside the dentine
*Usually NO groove retention is necessary unless …… (I’m really sorry I can’t hear it & this note isn’t written in last year sheets)
*Advantages of beveled conventional compared to conventional:
1- Provides more retention 2- Esthetic is better 3- More conservative because in beveled conventional we rarely put grooves 4- Provides a good seal (due to stronger bond between composite and enamel, therefore less micro leakage, sensitivity, caries and so on)
*Bevel is the final stage after we finish everything
*If there was a bevel but the walls are not 90 degrees so the cavity is modified
*Beveling is made using diamond high speed bur that is rough, round or flare shaped bur
*We can use straight diamond bur but we will have a problem in the palatal surface because it’s difficult to make the 45 degrees with a straight bur

3- Modified:
*It is preformed in restoring moderate class 5 lesions
*Lesions that are entirely in enamel like hypo-plastic (hypo-calcified) areas which are very small lesions or pits
*It doesn’t have a significant shape; it rather follows the shape of the carious lesion after removal
*If the patient has a non-carious lesion cervically we don’t have to do anything except bevel
*The preparation has a divergent configuration & the axial walls aren’t uniform in depth
*Because we only want to excavate the lesion without 90 degrees walls or uniformity so we use a round bur
*REMEMBER the mesiodistal divergence is more pronounced
*Increase in divergence means decrease in retention





Non carious lesions:
1- Erosion:

*This is dentine exposed (not caries) & there is some sort of cavity
*Appear as a result of some acidic drinks, ex. Soda, lemonade or grapefruit…
*We do modified cavity preparation (just bevel)
*Stomach reflexes are highly acidic and can cause erosion which is the case with bulimic and anorexic patients so the palatal surface is eroded in this case because it comes from inside not from outside

2-Abrasion:

*Loss of tooth structure by mechanical ways
*Usually result from tooth brushing
*Note: eating nuts can cause abrasion like lesion, but it’s not considered a class 5 cavity as it is found incisally
3- Abfraction:

*When the tooth is subjected to high forces that exceeds its capacity (heavy occlusion forces) which causes the teeth to flex
*Note: enamel hypoplasia isn’t considered as class V because it doesn’t happen cervically

-The cavity preparation of class V non-carious lesion is modified & you don’t have to do anything except for roughening the internal walls with a diamond bur
-So its not just bevel all the time we may do roughening of the axial wall with a round bur and the reason is that the external surface that subjected to saliva is hyper-calcified (very rich in fluoride) and it’s difficult to put composite to bind to it even if you put acid etching so sometimes you remove the external surface (microns) then you bevel all your margins
***Aberrant smooth surface pit form: it is not class 5, (not in the cervical area), it’s rather a lesion that forms a pit in the middle of the tooth buccally or lingualy, its preparation is modified not conventional


That’s all and I’m very sorry for this delay I was really busy

Done by: Ibrahim Murad Abdulghani
Dr.Suzan Hattar
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Shadi Jarrar
مشرف عام

عدد المساهمات : 997
النشاط : 12
تاريخ التسجيل : 2009-08-28
العمر : 26
الموقع : Amman-Jordan

http://jude.my-rpg.com

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