Class II preparation help

[MattBiggar80]

ok... the dreaded class II preparation on plastic teeth.

I've been going thru a funk and having great difficulty with my class II preparation in drilling (operative/restorative) class.

I wanted to know if you guys can give me some good tips.
We have a huge exam coming up and recently my work has gone to hell. I keep hitting he adjacent teeth, and the worst part is this:

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I get the gingival floor of the box to be flat but in order to get just a "little" more clearance, I need to remove a little more from the floor.
****

So now, I jam in 3,4 wedges (which keep breaking btw), and use my high speed (#330- we are only allowed to use this bur in my course) and try to lower the floor. I feel the bur is dull and doesn't cut. i keep putting apical pressure and then BBBBOOOOMMMM i make a hole on the floor and fail the exercise.


Thisis what happens on a maxillary molar usually.

If you guys have any good suggestions on how to get past this , that would be awesome.


Tips that I already have... so far


1. Color code your instruments - it will save you lots of time and prevent them from getting lost
2. Look at the handle of the drill. if it is parallel to the occlusal plane, you are not leaning too far distal or mesial
3. when looking in the mirror, you can only see some of the drill. if you notice that you start seeing more/less, you might be leaning distal mesial or buccal/lingual
4. To make sure you have converging B and L walls, put the mirror by the canine when doing lower molar. you can see your tilt easy. **if you tilt too much you will not get defined line angles on the walls... that is, you will get "rounded" gingival-buccal and gingival lingual line angles.
5. to check the prep sometime, you can pull the jaw really far downward and get a nice view. otherwise, use the mirror at a45 degree angle to the prep and look down along the occlusal plane (best view)
6. To get the last bit of clearn Buccal lingual, use the baby/small hatchet. DANGER: you can end up getting "choppy" walls. might be better to use the slow speed
7. To get sharp axiopulpal line angles (in the box) give a generous B/L til to the bur, use the skinniest bur you have, and aim in a Distal/buccal (towards the Buccal groove) when doing the Buccal/Pulpal/Axio line angle. (use similar technique when doing lingual side).
8. Change the direction of the slow speed (sometimes spins Clockwise, or counter clockwise) when working on the walls of the box. You can make it so it will spin towards the prep instead of spinning into the adjacent tooth (and then damaging it)
9. sharpen your instruments before timed drilling exam



I tried using a new 330 bur to lower the floor but it seemed to roughen up the floor

thanks!!

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[7 Iron]

They ONLY let you use a 330 bur for the whole prep? That's crazy. We use a 245 bur for the box to make sure it isn't too deep or shallow.

Do they let you use a slow speed handpiece? After you get your general outline form, try going over it again with the slow speed to make the cutting look smoother.

Use a hand hatchet to break contact interproximally--this will prevent you from damaging the adjacent tooth with a bur. Put a wedge between the two teeth--looks like you do this. Could you put a matrix band between them as well? That way if you scratch anything with the hatchet, it will be the matrix band instead of the adjacent tooth.

To check buccolingual convergence, look in your mirror straight down the occlusal. You should not be able to see your internal walls. If you do see them in any part of the prep, then that wall is divergent and you need to prep more to make it convergent.

Unfortunately, MOD's take practice, practice, practice.

 

[DrJeff]

Just a 330? How the heck do your profs expect you to make a flat pulpal floor prep with a ROUNDED bur tip? I will guarentee you that when they're prepping a class 2, if they're going for a FLAT pulpal floor that they're not just using a 330, but whatever their favorite flat tipped bur of choice is

 

[TeethRgreat]

Just a 330? How the heck do your profs expect you to make a flat pulpal floor prep with a ROUNDED bur tip? I will guarentee you that when they're prepping a class 2, if they're going for a FLAT pulpal floor that they're not just using a 330, but whatever their favorite flat tipped bur of choice is

OP never stated in his question whether it was a composite or amalgam prep. Maybe it's a composite fill so they wanted rounded internal line angles..? Either way, the teeth are plastic, you can make a flat gingival floor with a hatch...the pulpal floor is another story.

Burs get dull VERY fast on plastic teeth. You should be using NEW burs on EVERY new tooth. You might even have to use several...but itll stop you from having to push so hard.

 

[suarez 7]

Burs get dull VERY fast on plastic teeth. You should be using NEW burs on EVERY new tooth. You might even have to use several...but itll stop you from having to push so hard.

That's what I've noticed as well. I thought it was my technique or something, but I feel like I have to replace my 330/245 bur every tooth I prep on the plastic typodonts.. Really annoying, we use carbide burs.

Do you think they wont dull as much on human teeth?

 

[MattBiggar80]

Okay. first off, thank you for your responses!


1. yes only the 330 for highspeed . The slow speed can gets a straight fissure bur. it looks like a 56. 1mm in width. the 330 is 0.8 in width.
2. the pulpal floor at my school is NOT suppose to be flat. it is suppose to be uneven like the occlusal surface of a tooth. that means for a Mandibular molar, you will find that you descend as you move from the mesial marginal ridge area towards the central fossa. The first time I did a prep, i made it all flat and they said NOT to do that.

I believe this is a WRONG approach because if you do this the amalgam will not have a "triangular" cross seciton. instead it will be more rounded. I can elaborate on this more , but only with a picture. Perhaps you readers understand what I mean.

Also, they do not want the floor flat because they want 1.8mm depth at all points (1.5 to 2.0mm). By having the pulpal floor rise and fall you can maintain that 1.8mm uniformly. Otherwise the center part of the tooth can be 1.5 and the sides mesial wall can be high like 2.5mm

2. because the slow speed has a large 1.0mm diameter, when tilting it I make these little "steps" at the line angles. They are hard to get rid of. For this reason, I smooth with the 330. I generally press 1/2 down on the foot pedal.


3. I do not know what a 245 bur is. Online it looks like the straight fissure bur, similar to what we have. Our shank What does the shank look like? Ours is "big" and I think it is called "latch type"

As a bonus, forgot to add: we use water when drilling on plastic teeth. At other schools I know they do not.


4. I use the hatchet to break contact. I sometimes go occlusal gingivally. Because of this I can get interproximal contact EASY BREEZY. I also use a matrix to prevent damage to adjacent tooth. But I remove the matrix when I use hand instruments. Otherwise I can't see the precise contact.

The key thing is to have NOT just the straight hatchet but I encountered this "angled one" by accident. Instead of the nnormal straight hatchet. there is one that is twisted 45 degrees inward and anotehr that is outward. I


5. this is an amalgam prep. but from what i remember they are virutally the same.

6. I recently started replacing my 330 bur generously and it made a signficant the difference. there was a dramatic improvement in my preparations. i actually start with the distal box, then the mesial box on my MODL (MODP) for my MaxMolar 1 preps . I finish off doing the rest usually when the bur is dull.

On human teeth they do not wear down nearly as fast.

7. SHOUT OUT to DrJEff for doing Tough Mudder. I hope one day i get to do that obstacle course. I just dont want to go in the ice bath truck thing I heard about. sounds too extreme!

thanks again!

 

[Muggsy Bogues]

Hmm

 

[mmasurf]

i would suggest if your having issues nicking adj teeth to buy this product its a wedge with a metal cover. in real life you wont deal with this as you will get really good by the time you work on humans and your nicking experience become seldom.
hopefully they allow you to use this
http://www.garrisondental.com/news/tooth-shield-aids-minimally-invasive-dentistry.cfm

 

[Duriel]

i would suggest if your having issues nicking adj teeth to buy this product its a wedge with a metal cover. in real life you wont deal with this as you will get really good by the time you work on humans and your nicking experience become seldom.
hopefully they allow you to use this
http://www.garrisondental.com/news/tooth-shield-aids-minimally-invasive-dentistry.cfm

Instead of using something like this, he should probably just practice not nicking the adjacent tooth. In my school they teach you to make a "crab claw" of sorts and then use a hatchet or margin trimmer to take off the unsupported enamel.

 

[goffdent]

"It's the CLAW!!"

 

[MattBiggar80]

amazing picture. duriel.

i am now putting in 2 matrixes.. one maxtrix band and then i cut a little piece of another matrix and insert it inside the other matrix.
i also bought some new hatchets so i know that they are sharp. the ones i had before were just garbage.
i also bought something called an off angle hatchet. makes an incredible difference.

im also looking to buy a back action carver. it helps me get amazing anatomy on the DMR of restorations.

 

[Wax n Relax]

Ha, hatchets.

 

[txaggie03]

Most of dental school is just jumping through the hoops they hold up. It sounds like this is one of those exercises.

Take solace in this.

 

[jay47]

Haha, only a 330. If that's ALL you can use, then try to use a new one. Using old dull burs will cause you to put too much pressure, which will sink the bur further and perforate beneath the floor. Don't get too cheap, I promise $25 more of burs is a drop in the bucket compared to your student loans.

 

[MattBiggar80]

i go to school abraod. the cost here is cheap. they also want "financial equality". You are discouraged from buying outside materials.
but i bought new materials. I know of students who got caught with outside burs and got in serious trouble.

anyways the problem is solved. a new bur is VASTLY different even after 10-15min worth of use. I also bought some off angle hatchets and i come in from proximal surface and remove tooth structure -- that is i come in from a buccal direction and remove tooth structure pushing lingually on the mesial and distal surfaces. it helps me get clearance really fast.

HOWEVER.. for some reason on the distal of right mandibular molar 1, i CANNOT get clearance. everywhere else im doing great. its as iff the mandibular molar 2 keeps drifting into the box.
do u know what im talking about?
i switched out that tooth "31" and it still and the same problem.

 

[MattBiggar80]

problem solved

thanks guys. the advice of getting new burs made all the difference!
thank you so much!