Pedo Sheet #8 By Karam Elias

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Pedo Sheet #8 By Karam Elias

Post by Sura on 10/4/2012, 12:51 am

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Sura

عدد المساهمات : 484
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تاريخ التسجيل : 2010-09-29

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Re: Pedo Sheet #8 By Karam Elias

Post by Shadi Jarrar on 22/4/2012, 12:04 am

Pedo Lec.
5/4/2012
Dr.Hawazn.

The differences between primary & permanent teeth
Categories:
1) Crown morphology.
2) Enamel & dentine.
3) Pulp.
4) Root morphology.
5) Contact area.

*Why we need to know these differences?
It`s important clinically, there is a difference & it translate as a clinical difference so it reflects on what you are doing in the clinic.


««Primary teeth:
- 20 in #.
- A, B, C, D, E.
- 5,6,7,8 instead of 1,2,3,4.
- NO premolars, so we have central, lateral, canine, first molar &second primary molar.
- Primary molars are replaced by the permanent premolars & the permanent molars are distal to them.

A)) Differences in crown morphology:
-Primary teeth are smaller in all dimensions than the corresponding permanent teeth; they are smaller because the jaws are smaller.
-The crowns of the primary teeth are more bulbous (more circular or more round) than the permanent successor.
-Crowns are wider MD in relation to the crown length cervical-occlusaly, so they are wider.
-Primary teeth are bell shaped with a define constriction at the gingival margin.
* SO the D  has a constriction.
Cervical prominence (buccal bulge).
So the buccal bulge is important difference because you don`t see it in the permanent teeth.

©Clinical significance:
1. We use this constriction and the bulge to gain retention to the stainless steel crowns (ss crowns).
Basically SS. Crowns preparation you break the proximal contact & ooclusal reduction &then you do nothing buccally or lingually, because we want to get into that constriction to hold the crown.
2. When you are doing a class II preparation in a primary teeth molar & you come doing the gingival seat if you go too far gingivally because it`s constricted in this area & you come to clean the axial wall, you will end up in the pulp !.
(So we try to not to go far gingivally unless there is caries, & if this happens we have to change the treatment & do pulptomy in this stage).

-The buccal and lingual walls coverage toward the occlusal surface, so we have an oclusal surface that is smaller in all diameters cervically.
So the occlusal table is narrow.

©Clinical significance:
*We have a narrow table so when you do your cavity it has to be minimum we don`t want to destroy so much from the tooth especially when we are dealing with the occlusal isthmus.
*The guidelines are the 1/3 of the intercuspal dimension from the high of the cusp a 1/3 from that distance.

Again… this means when we are drilling in a primary teeth, we want to be conservative, we use very small burs so that we don`t over prepare & when we have to overextend the cavity
 We will have unsupported enamel & we will have a failure of the restoration.
And usually in cases when we have a filling or caries that is wide, we prefer to do a SS crown because the filling will eventually fail.


Clinical significance of crown morphology:
Buccal bulge (buccal and lingual preparations are NOT required).


………………………………………………

B)) Differences in enamel & dentine:
1. Thinner in primary than in permanent teeth & they are equal in the thickness
Enamel = Dentine.
And you look at the primary enamel, you expect 1mm and then you will end up in the dentine, while in permanent teeth you need about 2.5 mm to actually reach the dentine
SO…Primary  Enamel= 0.5- 1.0 mm
Permanent Enamel = 2.5mm
So in primary teeth, we have less amount of enamel to end up in the dentine, also we have less amount of dentine to end up in the pulp  so less thickness of enamel & dentine.


2. Enamel & dentine are uniform in thickness and they follow the DEJ, while in permanent teeth there are areas of thin enamel and areas where enamel is thick.

3.The water content of the primary teeth is greater than that in the permanent,& that means it translate a different color and the teeth will appear whiter (or bluish-white) compared to the permanent teeth which are more yellowish in color.
So, sometimes you might find the teeth look whiter and sometimes the parents will actually say: why the primary teeth look whiter? What is wrong?
So you have to explain to them that this is normal, and the primary teeth are usually whiter than the permanent which are more yellowish.

©The clinical significant of 2&3:
1) It`s easier to cut take less drilling for you then you would expect in permanent teeth.
2) There is less tooth structure protecting the pulp so it`s easier to end up with pulp exposure.
-Mesial surface of the mandible D takes about 1.6 mm before you end up in the pulp
-Mesial surface for the mandible E =1.8mm
So it`s a very small distance, and usually class II mesially will end up in the pulp of the D & E.
3) We need to diagnose caries as early as possible before it reaches the pulp, & that is why we like to, even if we can`t see caries, take bitewings radiographs so we can detect caries before we can see it visually esp. when the contacts are closed, there are some stages where the contact will be opened and we will be able to examine the surface visually But when they are closed we can`t see them and we will need radiographs.
4) Small burs330 bur, and actually you can do most of the preparations using this bur, it`s small, short and it`s not a fissure bur…. So you can do pulptomy, class II ….. With this bur.
5) The enamel is directed occlussaly esp. in the gingival third, what is the clinical significant of this point?
We don`t need to do a cavosurface bevel like what we do in the permanent teeth& this make it easier when you prepare the cavity.
We want the gingival seat to be parallel to the orientation of the rods.
So we don`t need to do a cavosurface bevel.

C)) Pulp:
1. The pulp is proportionally larger in primary teeth than the permanent teeth, because we have fewer amounts of enamel + dentine, so most of the tooth is made from pulp.
2.Pulp horns are larger than those of the permanent teeth, so it`s goings to be extending closer to the occlusal surface & they are situated below the cusps.

• So the pulp horns are high, what that means:
A. Is that the when you are doing a cavity, you want to make sure that u can visualize where the pulp horns are, and try not to expose them, so that we always like to have a preoperative radiographs.
B. We use the pulp horns to get access to do pulptomy.







Pulptomy: You remove the roof of the pulp chamber (you remove the pulp) & basically you leave the radicular pulp in place.
SO… When you do a cavity and you remove the caries,you will see red dots (pulp horns), so finally you connect the 2 dots & by doing so you remove the roof of the pulp& gain access below them.
So.. it`s an easy way to know where you are when you are doing pulptomy.
NEXt … you excavate the pulp either by: 1. Excavator.
2. Slow speed round bur.


Q/ Why we don`t do pulptomy with permanent teeth?
A/ because there are differences in the pathology of the infection& also it has to do with the root canal morphology.

**IN pulptomy the tooth is VITAL.


• Basically: we do pulptomy in a vital tooth with irreversible pulpits if there is pain or if you have exposed the pulp during the preparation of a cavity (large cavity).
• {If the caries is so deep you have to remove the caries &you will end up with pulp exposure and the tooth is not inflamed, so you do pulptomy}.
• SO  in the radicular area the pulp is vital ( imp.).
• Now  if you have a non-vital tooth, you do pulpctomy.
• SO… in pulptomy the tooth retain some of its vitality.


Pulp physiology:
*Pulp aging:
The pulp in primary teeth is also like the pulp in permanent, so the pulp can have :
-Secondary dentine.
-Internal resorption.
-Pulp stones.
-Calcifications.
* The size of the pulp will actually change in terms of the age of the child, because of secondary dentine formation.
So the pulp in a 3 years old child is larger than the pulp in an 8 years old child of the same tooth, so there will be secondary dentine formation and the pulp will become very thin & usually as the child gets older it`s harder to do pulptomy because it`s going to be more difficult to remove that tooth structure without damaging the floor, so you have to be careful when you do pulptomy in an older children.

D)) Root morphology:

- The pulpal floor & the accessory canals that means instead of having a preapical area like what we have in permanent teeth, we`re going to have an interadicular bone loss or abscess.
- So in D with a large caries lesion, the teeth are non-vital and the tooth has an inflammatory area in the interradicular area & result in an abscess.
- So it`s different, we don`t get a preapical lesion that you used to see in permanent.
- So basically, we are dealing with the crown area rather than the apical area.
- Roots are slinder & very long, thin and very close to the permanent successor ( imp.).
- ©Clinical significant:
During extraction you have to be careful and don`t dig with the elevator to prevent damage to the permanent below it, and if there is an infection we`ll be afraid from the effect of infection on the permanent (turner tooth) and we mostly see it in the 5 because the E are usually infected for a long time and the parents don`t do anything about it and at the end the 5 will be damaged.
It`s one of the way that you can explain to the parents the importance of the treatment of the primary teeth because at the end you want to preserve the health of the permanent tooth (one of our goals is to maintain the health of the permanent dentition).
If there is trauma (intrusion: inward, or avulsion: loss of the tooth) so this kind of trauma can damage the permanent teeth esp. the most severe form of trauma1.avulsion. 2. Intrusion.
When you treat avulsion in a primary tooth, basically you wait & you don`t reimplant the tooth and you don`t need a space maintainer in the anterior teeth.
So you don`t need to reimplant, splinet difficult to do and you risk damaging the permanent with the motion of entering.
*We don`t need a space maintainer for anterior teeth, because when you are talking about space maintainers we are dealing with mesial drift (esp. with the post molars, if you extracted an E, the 6 will move mesially) while in anterior teeth the labial motion isn`t present.
BUT, you may see an aesthetic appliance (appliance that replace ant. Just for aesthetic reasons not for space maintainer.
*The molar roots are flared, because the permanent successors are underneath so you have to be careful during extraction, you don`t want to damage them and you don`t want to use an elevator, sometimes you might need it but you must use it properly, and sometimes when you have a fractured tooth& you can`t remove the root you should leave it, it will resorp when the permanent is erupting & there is no need for a flap or to drill the bone or the root.

*We said that we have thin roots, which means we have thin radicular pulp as well and when they did a CT scan of the radicular pulp they found it: 1. Thin
2. Tortuous.
3. Branching.
4. Systems that are ribbon shaped.
5. Apical portion was not that constricted.

So … at the end it means that : it’s more difficult to do an endodontic procedure on roots because they are so thin and we need to do an endodontic procedure that involve the radicular pulp we have to modify the technique that we use in permanent teeth…so we have to be careful, & we also put a resorpable material in the root & you have to be careful when you do filing and there is a limit for the # of files that you use in primary roots, & if you use large file size you will end up with …?.... (remove part of the root)
Usually size 35 is the maximum when we are doing a pulpctomy procedure, and you have to be careful when filing not to damage the permanent tooth.

*There are stages of physiological resorption of the primary:
-6 is erupted
5 is resoping the E, and it doesn`t need to be extracted because it is normal.
-While in the permanent teeth if you see resorption of the root, it`s usually pathological (there is something wrong) so there is a difference, so you need to know again the resorption in primary is normal & you don`t have to do anything.

E)) Contact areas:
* The difference here is that the contact is area NOT a point, so it `s flat and broad & it`s more gingivally situated.
* What that’s means?
When we have a proximal lesion it`s more extensive before you can see the grey shadow that you used you use to see in permanent teeth, because we are talking about a large area, so it takes more destruction of the dentine to get that grey shadow that you see in permanent teeth.
Again it means: when you do see a grey shadow, it means that there is an extensive caries & because of that usually when you are removing the caries you might end up with a pulp exposure, so it`s best to take a bitewing before to detect proximal caries as early as possible.
And usually when you see a broken margin ridge most likely you are going to get a pulp exposure when you are removing the caries, again it is best to have a preoperative radiographs b4 you do anything, because it takes less before you end up in the pulp esp. in contact area.

AGAIN  Bitewings, you defiantly need to take bitewings even if you don`t see any evidence of caries, you should take your bitewings.
When you are preparing a class II cavity, you need to extend the buccal and lingual walls far enough to break the contact, so you can actually pass between the teeth & you have a clean margin.

*IN the end:
You have to know the differences, it make a difference on what you are doing & it`s going to influence on your cavity design and on the restorative material and on your treatment options.


The end
Good luck ^_^

Done by: Karam Y. Elias
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Shadi Jarrar
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