Scr.2 Access Cavity

7/29/2019 Scr.2 Access Cavity

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Access cavity

Nawaf Hazaymeh

Aya Shahrouri

Sun. 17-2-2013

2


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In the name ofGOD

access cavity preparation

Access cavity means entrance, so we won't be able to reach root canals , or

root canal system without accessing the crown , it's the only way to reach or

to enter the root canal system by mean of access cavity through the crown.

As u can see from the diagrams shown in slide #2, it's a diagram for a molar

tooth and in order to reach the root canal system we need to open through

the occlusal surface of this molar. Each tooth has a different design of access

cavity preparation according to the morphology of the pulp chamber, so from

you're dental anatomy knowledge not all teeth has the same access cavity, so

the central incisors different than canines as well as different from the molars.

Why do we need to make an access cavity for root canal treatment?

first of all we need to Remove roof of pulp chamber in order to get access to

pulp chamber or to the root canal system, so before u start drilling, you need

to carefully assess the tooth itself by means of radiographs and as well as

examination, so you need to look at the pre-operative radiographs to assess

the suitability of this tooth to be treated or the suitability of this tooth for RCT.What do we look for in the radiographs??

1. First of all we need to make sure that root canal system is patent, whatdo I mean with patent?? not calcified or closed

2. We need to look at the morphology of the pulp or the root ** couldn'thear, so you need to know wither this root is straight or sclerosed or

calcifiedor partially with a pulp stone, so to know your way and to

predict the success of your treatment wither it's going to be really

successful treatment or it's going to be a failure from the beginning and

you are wasting your time3. And you need to look if the tooth is restored , is the restoration is

successful , is there a carious lesion beyond it

4. U also need to look the shape of the pulp chamber and the its locationbeside if its obliterated or smaller in size due to the age factors , and to

the pulp horn how far it's extending in order to determine where your

access cavity will be.

And we should know if this tooth will be easily isolated or we'll have

challenges in isolating it, also as we know we always should isolate the

tooth before entering the root canal system in order not to keep


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contaminating these canals, we need to have a septic condition or sterile

canals, otherwise what's the point behind treating these canal systems .

So from the principles of root canal treatment, why do we need to treat

the canal system what's the object behind the treatment?? First of all we

need to eradicate all microorganisms from canal system for being a sourceof infection to the peri-radicular areas, so if we don't isolate the tooth it

may affect the percentage of successful treatment of this tooth.

How do we isolate a tooth for root canal treatment??

Rubber dam is the most suitable way and if there is no enough coronal

tooth structure we won't be able to apply the rubber dam.

When you want to start drilling your tooth for access cavity preparation, if

there is any carious lesion you need to remove it, and always remember

that we need to avoid contaminating the root canal system by isolation,

removing any necrotic tissues and eradicating any focal infection.

If you felt that there's no enough tooth structure for applying the rubber

dam, then you may consider applying a durable filling like GIC, amalgam.

What are criteria for cavity access preparations?

first of all we need to remove the whole roof ( d-roof the pulp chamber) in

order to have a straight line access for the canals , we need to insert or use

our root canals instruments in a way of easily inserting it into the canal

without forcing them into the root canal system , if we fore them it willbreak if you break inside the canal it will be a nightmare for you as a

dentist and for patient as well as the endodontist you will refer this case

to, it can be removed if the patient is lucky, if you're lucky as well , but it

will take time

NOTE :

when you do the d-roofing you should achieve this step without touching

the floor of the pulp chamber, touching I mean with the bur, IF you touch

the pulp chamber with bur whenever you place the file it will engage, andif you think this is the orifice you'll penetrate or perforate the pulp

chamber, the floor will guide you or will guide your finger according to

your knowledge to the location of the canals orifice.

After d-roofing and making the access cavity neat and nice you'll be able to

see the orifice as in slide #5, when we want to do an access avity we need

to involve the whole pulp chamber walls in the cavity if you leave little bit

of pulp chamber roof and it will act as a shelf, you won't be able to remove

these necrotic tissue from underneath , as the diagram in the middle of

slide #6 ( that angle circled in red) , in this case we need to involve the


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wall above and below that angle in order to have a straight line access to

those roots as well as removing all necrotic tissues in that area.

Just to emphasize again, the access cavity is a very crucial step in

successful RCT , if you couldn't make it nice and neat, you'll face difficultiesin the following steps.

for example in this case (in the diagram below) we have two root canals

buccal and palatal canals, access cavity should involve both orifices and, so

in this case if you want to insert your file to this direction ( green arrow) , it

will reach this point and If you want to push it again you'll end up with a

perforation or penetration or at least you'll create a LEDGE : it's a

procedure error you may create by forcing the file into the canal system

where it's not in a straight line access with the root canal, what do we

need to do ?? we need to remove that angle in order to insert our file

correctly. So it would be much easier to reach the apical area.

So what do we need to have before starting our cavity preparation??

1. Pre-operative radiograph2. A knowledge of the pulpal anatomy


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3. Magnification aims in order to help you see clearly and locate orificesand canals, because we work in a tiny areas and we need to have a sort

of magnification that helps us to know where to insert our instruments.

NOTE: loupes are not less than 500-600 USD

Different types of magnification loupes

Stages of cavity preparation :

first we need to find the pulp chamber and we need to locate canals and

we ensure adequate access to the canal orifices, as I said in the beginning

each tooth has its anatomy a different shape and size of pulp chamber and

in order to that u make access to the cavity, the only way is to go through

the occlusal surface if you want obdurate the whole canal system.

(central incisor: if you look from the labial view , you need to involve these horns

therefore the shape of your access cavity for a central incisor will be triangular

shape, base incisaly and the tip above the cingulum from the palatal side, of

course you're not gonna access cavity from the labial side for a central incisor,

would you accept somebody to make your root canal system from the labial side

?!! if you accept it will be very difficult to achieve a straight line access!)


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(Thats for a canine, it's different, it will be in the centre. from the lingual side it

will be oval in shape and in the centre and it doesn't need to be extended to both

mesially and occlusaly slopes because there is no pulp horns or pulp tissue under

that area)

Just a quick revision for the objectives :

*by making the cavity access we'll have a Straight line access and that will

Improve instrument control and handling and that will :

*Minimize curvature and deflection of the instruments and at the end we'll

have a safe journey to the apex. and if you control your instruments you'll :

*Decreased procedural errors like:

-Ledge formation

-Apical perforation

-Stripping perforation* also we need to Conserve tooth structure, we don't need to involve un-

necessarily structure in deep access preparation for the sake of getting

good access to the root canals or orifices. The access cavity itself will not

decrease the strength of the cusps for a great amount, now it will affect the

tooth itself I can't deny it- but making the access cavity as small as could

be, keeping in mind involving the whole pulp chamber.

HOW to do it??

A. as I said you make access from the occlusal surface, you do a class 1

cavity procedure using round bur just to make outline, then you can

penetrate the pulp chamber by a straight fissure bur.

there is no standard burs for making cavities, we can't say this bur is

better than the other in making that cavity.

from the Dr experience : use round bur first to outline the shape of the

acces cavity then use a straight fissure bur, this is a good procedure.

B.once you penetrate pulp chamber I advise you to penetrate always the

largest canal. For example in the UPPER MOLAR, the largest canal is the

palatal.


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C. so you direct the tip of your hand-piece toward the palatal canal, you'll

feel like a drop, when there is empty space under the bur you'll feel like

your hand-piece will fall or drop. control it not to touch the pulp floor as I

said earlier, and follow the outline you drilled in the first stage.

once you penetrate you need to negotiate(not sure, but thats what I

heard) the canal orifices using endodontic probe to see if the orifices are

open, then you need to insert the small size file, and as I said I need this file

to go straightly without binding without curvature and without forcing it, if

it bends in one area it will either break your instrument or you'll have

stripping.

now here :

( if u didn't remove this black area either you'll straighten this part of the

root canal system, or you'll penetrate and perforate the root to the side)

Q: what's the difference BTW the ledge and the stripping??

A: ledge when you don't have a straight line access, so it will creates an

angle in the dentin inside the canal and whenever you inside the file again

it will engage, so you won't be able to bring it back to the canal and if youforce it will perforate the canal, and the correction of the ledge is really

time consuming.

Stripping when you keep inserting and bringing out the file in this

area you'll end up with straighten it and you perforate to the furcation area

or to the buccal or lingual area in a straight line rather than it's just on the

tip of the file.


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Zipping: the file reaches the tip of the root and if you force it the tip will rotate

in a large area not, so it will larges the part above the root apex and if you

continue it will make an apical perforation.

**Lecture on next Sunday will be in NG76

**In the Lab of this week you should bring the jaws in order to learn how toapply the rubber dam

Done by: Aya Sharouri

Scr.2 Access Cavity

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