Crown prep - Help please!!

[AlphaOmega2]

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Two weeks ago i did my first crown prep for a full veneer crown on a first lower molar on acryl tooth (on phantom lab).
And tomorrow we have an exam on a crown prep for a lower first pre-molar.
As they told us a week ago, i had no chance to practice before the exam. I have no idea how i am going to pass.
And besides that we have to hand in an acryl provisory crown for tomorrow, on the molar that we did two weeks ago. That's why i had no time to practice for the prep.

Today we have 3 hours practice in the phantom, which i need to finish the acryl crown and also practice the prep on the pre-molar.

So, if you have any tips for tomorrow how not to screw up and do a minimally decent crown prep on a lower first pre-molar i would really apreciate it.
Thanks

 

[AlphaOmega2]

Any videos or pictures would really help
Thanks

 

[Daurang]

Make sure the temp is not hyperocclude! You can have the ugliest temp and still pass (on the board) but hypercoclude and it's automatic fail.

 

[armorshell]

What on earth is a phantom lab and where do I get one?

 

[mamelons]

Do not over taper the buccal or lingual. Keep referring back to the adjacent tooth to make sure you are prepping in the long axis of the tooth. And I don't know how your instructors grade, but make sure it looks pretty, smooth, rounded line angle, round off sharp points (cusp tips), etc. I like to use a green stone or white stone on slow speed with very little pressure on the reostat to smooth the prep, and then to round of sharp points I use the small football shaped carbide bur (7404 I think), again with very little pressure. Seems to work well for me. Good luck.

 

[dentstd]

a day to practice acrylics, don't bother. you're gonna fail.

 

[desert rat]

Matrix bands in the interproximal to prevent touching the adjacent tooth(only do this on models, not in the mouth). A football diamond for the occlusal reduction.

If you have access to it, durifinish by parkell to paint on the temporary to give it a super high shine. If you don't have that, unfilled resin can be used if painted on very thin.

 

[Dukie]

a day to practice acrylics, don't bother. you're gonna fail.

Well, aren't you just Susie Sunshine?

 

[Thaxil]

I have never like the idea of wedging the prox tooth or placing a matrix or even using an needle bur as I was instructed to do when breaking the contact. The easiest and fastest way to break the contact is to blow though it with a course chamfer bur in one motion. This is possible due to the cervical constriction. Just focus on the marginal ridge and place a tiny sliver of tooth btw the proximal tooth and the bur. If you practice this, you will save tons of time and end up with an untouched proximal tooth and perfect taper, just touch up the margin at the end.

 

[UCSF2012]

I have never like the idea of wedging the prox tooth or placing a matrix or even using an needle bur as I was instructed to do when breaking the contact. The easiest and fastest way to break the contact is to blow though it with a course chamfer bur in one motion. This is possible due to the cervical constriction. Just focus on the marginal ridge and place a tiny sliver of tooth btw the proximal tooth and the bur. If you practice this, you will save tons of time and end up with an untouched proximal tooth and perfect taper, just touch up the margin at the end.

This is my baby. Cuts at about 3x the speed of a course diamond. Of course, you may run into problems of control, since it wasn't designed to cut plastic teeth. Not the best for interproximals, thou. Still shopping for a good bur. Currently using a course 012 diamond for that.

What do you use to separate the adjacent teeth? just that aluminum wedge?

 

[djeffreyt]

This is my baby. Cuts at about 3x the speed of a course diamond. Of course, you may run into problems of control, since it wasn't designed to cut plastic teeth. Not the best for interproximals, thou. Still shopping for a good bur. Currently using a course 012 diamond for that.

What do you use to separate the adjacent teeth? just that aluminum wedge?

Wedges? That's like bowling with bumpers.

 

[UCSF2012]

Wedges? That's like bowling with bumpers.

If it takes bumpers for me to bowl a 300, so be it. Bumpers it is.

 

[AlphaOmega2]

Thanks everybody for the tips
I passed the exam with 72/100.
I lost most of the points because i damaged adjacent teeth on both sides.
It was the third time in my life that i did a crown prep, so just passing the exam was good enough for me

 

[tinman831]

Thanks everybody for the tips
I passed the exam with 72/100.
I lost most of the points because i damaged adjacent teeth on both sides.
It was the third time in my life that i did a crown prep, so just passing the exam was good enough for me

Smoothing out the adjacent teeth with a polishing disk or prophy cup coulda saved you a few points. 😉

 

[Count Orlok]

Smoothing out the adjacent teeth with a polishing disk or prophy cup coulda saved you a few points. 😉

Not when your instructor paints your adjacent teeth with nail polish.

 

[youngmc27]

Not when your instructor paints your adjacent teeth with nail polish.

man that sucks. We are going to have our first crown prep exam and it is a difficult one we are doing a reverse 3/4 maxillary crown prep and a povisional in three hours. I hope that I can pull a 72 I would be excited.

 

[DDSjunior]

Thanks everybody for the tips
I passed the exam with 72/100.
I lost most of the points because i damaged adjacent teeth on both sides.
It was the third time in my life that i did a crown prep, so just passing the exam was good enough for me

Interesting, if you damaged the adjacent teeth in a practical at my school you would have gotten a 0/100. And unless you were given a gift by god and just phenomenal at preps, only doing three crown preps would have almost certainly gotten you a failing grade.

 

[armorshell]

man that sucks. We are going to have our first crown prep exam and it is a difficult one we are doing a reverse 3/4 maxillary crown prep and a povisional in three hours. I hope that I can pull a 72 I would be excited.

Why would they have you do such a weird, difficult prep as your first one?

 

[mamelons]

Smoothing out the adjacent teeth with a polishing disk or prophy cup coulda saved you a few points. 😉

That would be nice, but we are not allowed to have rubber polishing points or disks of any kind out during the practical.

 

[mamelons]

Interesting, if you damaged the adjacent teeth in a practical at my school you would have gotten a 0/100. And unless you were given a gift by god and just phenomenal at preps, only doing three crown preps would have almost certainly gotten you a failing grade.

That is surprising to me -- there are a lot of dentists (even our instructors) who admit to hitting the adjacent teeth on occasion in their practice... nothing that a little fluoride varnish can't fix. Now if you alter the contour of the adjacent tooth to where it needs a restoration, that's a different story.

 

[youngmc27]

Why would they have you do such a weird, difficult prep as your first one?

That is what we all want to know.