endo sheet # 5

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endo sheet # 5

Post by Shadi Jarrar on 18/10/2010, 2:51 am

بسم الله الرحمن الرحيم

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بسم الله الرحمن الرحيم
Access Cavity for Maxillary Molars

Today we are going to talk about:
Maxillary 1st molar, maxillary 2nd molar and maxillary 3rd molar access cavity.
>> a quick revision for the last lecture :
We talked about maxillary and mandibular premolars last time.
Upper 4 >>
26% one canal, 69% two canals and 5% three canals

** Mesial concavity in root, beware of perforation.

Upper 5 >>
70% one canal, 25% two canals and 1% three canals
** Roots are close to or inside the maxillary sinus.
Lower 4 >>
74% one canal, 25.5% tow canals and 0.5% three canals
** Root and canal are oval in cervical third then tend to become round.
** Larger buccal pulp horn (while in the other premolars lingual one is larger)

Lower 5 >>

87.5 % one canal and 12.5 % two canals

Lower premolars:
>> Usually have extreme variation in anatomy.
>> Canal configurations types I, IV and V can be seen.
>> We start our access cavity perpendicular to the occlusal surface then we continue parallel to the long axis of the tooth.
First of all we talked about Unroofing:
The Unroofing process is more noticeable in the posterior teeth (premolars and molars) than anterior teeth.
Steps after drop-in by high speed bur: using a low speed round bur and enter it through the hole we make when we penetrated the pulp chamber and lean it to one of the walls then with and outward strop (withdrawal movement) we remove the roof completely, then using a low speed fissure bur we make proper finishing for the access cavity walls without touching the floor of the pulp chamber.
Upper 6 >>
- It is the largest tooth in volume and among the most complex in root canal anatomy
- The pulp chamber is wider buccolingually than mesiodistally
- 4 pulp horn can be identified; mesiobuccal, mesopalatal, distopalatal and distobuccal.
- The shape of the pulp chamber is rhomboid not rectangular.
- The occlusal table is also rhomboid in shape.
- Usually it has 3 roots; mesiobuccal, distobuccal and palatal.
- The orifices are also called palatal (P), distobuccal (DB) and mesiobuccal (MB) but sometime we a 4th canal, where 2 canals will be found in the mesiobuccal root and they are called MB1 and MB2 or mesiobuccal and mesopalatal (or mesolingual).
- The angles of the orifices:
o Mesiobuccal > acute angle
o Distobucaal > obtuse angle
o Palatal > right angle and is usually centered palatally.
- MB is found mesial and buccal to DB
- If there was 4 canals, the MB2 is usually found mesial and palatal to MB1
- Molar triangle: is a triangle drawn to connect all the three main orifices ( MB, DB & P)
- Access cavity outline is triangular if we have 3 canals, and rhomboidal if we have 4 canals.
- Shape, location and size of your access cavity depend on the number and location of the orifices.
Palatal root >>
- Palatal canal is biggest and easiest to access
- Usually there is a curvature buccally in the apical third of the palatal root
- Usually it has ONE canal.
No. of canals Vertucci 1984 Thomas 1993
One 100 % 99 %
Two 0 % 1 %
- If we found one centered big orifice then it has only one canal but if it was small and located more toward mesial or distal then we suspect the presence of a second canal.
Distobuccal root >>
- It is conical in shape
- The canal starts oval then become rounded as we go apically
- Its orifice is oval in shape
No. of canals Vertucci 1984 Thomas 1993
One 100 % 96.5 %
Two 0 % 3.5 %

Mesiobuccal root >>
- May have one, two or three canals.
- If we have single canal the orifices is oval in shape and wider buccolingually, but if we have 2 or 3 canals orifices is round.
No. of canals Vertucci 1984 Thomas 1993 Neaverth 1987 Smadi 2007
One 82 % 73.6 % 37.7 % 77 %
Two 18 % 26.4 % 61.9 % 23 %
Three 0 % 0 % 0.4 % 0 %
- The percentages depend on the population that the study was based on. In general, about 3/4 have 1 canal & 1/4 have 2 canals.
- No. of discovered canals depends on the orifice locating method.
- Orifice locating methods include low and high speed burs and files, special instruments like special burs and microscopes.
- A research was made "bulken" by 1983 stated that :
o 50 % of the upper 6's have 2 canals by visual inspection.
o 85 % using special endodontic burs'.
o 95 % using microscope.
- MB2 sometimes is covered with dentine called dentine ledge or shelf, so we should remove this ledge in order to find MB2.
- Usually there is a grove palatal to the MB1, we do some roughing in this grove in order to find MB2 (using a small round bur we drill in this area 1 to 2 mm in depth).
- MB2 is usually almost 1.8 mm far from MB1.
How do we do the access cavity?
There are some mesial and distal boundaries for your access that you shouldn’t cross unless we have to.
- Mesial boundary is a line connecting the mesial cusp tips.
- Distal boundary is the oblique ridge.
Steps to do your access cavity:
1- Removing any caries or restorations.
2- Starting with a round or tapered fissure high speed bur perpendicular to the occlusal table until we feel drop in. ** Penetration should be toward the largest canal, which is the palatal canal…Why!! Because if we found the largest one then it is easy to use it as a start point in searching for other orifices.
3- Unroofing using a low speed round bur.
4- Locating the orifices. ** The no. and location of orifices determine the shape of your access cavity. 3 > triangular , 4 > rhomboidal …
5- Removing of the cervical dentine bulge if we have it using high speed fissure bur or using Gates Gliden files.
6- Finishing of the walls of your access cavity using low speed fissure bur.
Upper 7 >>
- Coronally the shape of the crown resemble the upper first molar but smaller in size.
- The roots also resemble to the upper first molar but smaller, shorter, less curved and closer to each other or maybe fused.
- The main difference between upper6 and upper 7 that the distobuccal is more mesially & buccally located than in upper 6. ** So the molar triangle is not very clear, and the 3 main orifices may be found in line with each other .
- Mesiobuccal is more to the mesial and to the buccal in upper 7.
- Palatal is most palatal and the distobuccal approaches the midline between mesiobuccal and palatal.
- No. of canal in the mesiobuccal root in upper 7
No. of canals Vertucci 1984 Pecora
One 88 % 80 %
Two 12 % 20 %
- We should look for MB2 in upper 7.
- Distobuccal and palatal is 100% one canal in both studies.
- If we have fused roots (either the distobuccal with mesiobuccal or the distobuccal with palatal), sometimes we have 2 canals only so the shape of the access cavity is oval in shape. If 3 canals were found it is triangular , if 4 > rhomboidal …
- Distal and mesial margins shouldn’t be exceeded also.
- The access cavity steps are the same as in upper 6.
Upper 8 >>
- Usually don’t have a specific anatomy.
- Root canal treatment is done in some case; if it is used as a abutment for a bridge and the opposed lower 8 functional.
- Carefully study for its root anatomy and morphology is essential.
- It might have 1 – 4 roots and 1- 6 canals.
- Access cavity outline can be oval, triangular or rhomboidal …

** In one of the pictures that the doctor showed us, the tooth showed 5 canals P, DB, MB1, MB2 and MB3.
** In another picture, MB2 was located more toward the palatal (more than 1.8 mm far from the MB1).

Some questions asked by students:
What is gouge?
A: it is unnecessary cutting or over cutting of tooth structure; to remove some tooth structure that is shouldn’t be removed.
What is the metal that we can see around the tooth in the pictures?
A: It is called clamp, underneath it there is the rubber dam sheet which is used for isolation of the tooth. So no saliva will come in contact with the tooth to avoid contamination with bacteria or if a file dropped of your hand as not to be swallowed or inhaled into the lung it will cause some serious problems.

Note: am really sorry but am not sure if scientist name "bulken" is correct (page 4, line 3). Check it from the slides please.


Mohammad H. Bustani
Endo. lecture # 5

Last edited by Shadi Jarrar on 20/10/2010, 2:23 am; edited 1 time in total
Shadi Jarrar
مشرف عام

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


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