Acrylic Temp Crowns – please give me some advice.

[MattBiggar80]

Acrylic Temp Crowns – please give me some advice.

I can't put into words how much I HATE working with acrylic temporary crowns. The smell, then waiting 6 minutes for it to harden during the timed exam is just a nightmare.

Anyways, you guys have given me excellent advice for restorative - amalgam preparations and also some crown and bridge advice.... here's the next question.

There's an open margin on the buccal of my temporary white acrylic resin crown that I am making on the upper right max molar. I use a "salt and pepper" technique. I dip my metal spatula, into the liquid, then dab the powder and apply it to the temp crown which is sitting on the tooth. Now I have to wait 10 minutes for it to harden. Very frustrating. Now i've waiting 6 minutes because Its a timed exam and I gotta hurry! I take off the crown and proceed to get rid of the over hand.I come VERY slowly at the margin (90 degrees). (not in a direction that I am touching the buccal surface). As i try to remove the over hang the entire piece that I just added flies off. Now i'm back to where I started. Damn!
Okay.. so now what? I make another batch of acryl powder and liquid. this time its very liquidy and I put it on the margin of the temp crown itself and i slam it onto the tooth.. I move fast because this liquidy stuff is sloppy (this is before it gets to the “fiber” stage where it is doughy). I put the temp crown onto the tooth. I take the spatula , dip it in some liquid and try to "wipe" the excess. I am afraid that I am pulling the material and making things worse so I dont touch it. I wait another 6 minutes... after 5 minutes I start working again because I'm just so damn nervous because the timed exam is almost up! I can see that some of the material jumped onto the buccal surface and gives the tooth an ugly appearance on the buccal. I start to trip the excess again, but this time I trim with the bur grinding from the buccal surface (thinning out the buccal wall). I put the temp crown back onto the tooth and now the entire lingual surface is a giant open margin. I look on the inside to see if there is any debris and i spray air ,but this has no effect. I panic some more. There is still a giant lingual open margin. I figure I can't win this “open margin” battle so let me work on the occlusion. The entire crown is now seated too high. I start to grind the occlusal surface and the anatomy starts to look uglier with time. Eventually I get very nervous because when I take the temp crown off, I can see that the acrylic temp crown is getting dangerously thin.. which eventually cracks!
Now im looking at the timer and everybody else is polishing their crown because the exam is almost over. I have sealed buccal margin but that looks sloppy. The “extra” that I added ended up on the buccal surface and it doesn’t look uniform with the rest of the acrylic temp crown.

I hand it in and I score a 30 out of 100 and fail the test.

Any tips for this stuff?

I want to note that this was the result of my last exam. The time before it I ended up doing decently but I can’t duplicate that result. I remember making a ball of acrylic and then putting it onto the tooth (we are not allowed to use impression/mold – must all be done free hand). After 2 minutes, before it gets fully hard, I make another batch of white acrylic that is still kind of liquidy. I put it immediately onto the previous ball of acrylic and try to get the margin complete on 1 shot. I use my metallic dental spatual and push the acrylic resin towards the Mesial and distal borders. This is the place most likely to get a missing wall. Somehow, someway this time the entire margin came thru. After 10 minutes of waiting, I mark with a pencil the margin, shave towards that area and it all worked out. I scored a 65 because I didn’t have time to lower the occlusal surface (there was a heavy contact) and there was slight open margin on the lingual.

I ask my classmates for advice but it doesn’t help. They say to do what I did—the salt and pepper or “venting” (remove from inner surface, add a bunch of liquidy monomer/powder, then sit onto tooth; while it hardens they use explorer and wipe excess). When I do venting, some parts shrink on me and mess up the margin again.

Thanks for advice!

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[SoulPower]

I'm no pro myself or anything but just a few tips I've picked up with the 10's of hours I've worked with acrylic.
1) If you get a bad initial temp off your first pull. Just throw it out. There is no sense spending a ton of time trying to fix something that is f*** from the start.

2) When you are about to do a reline procedure, make sure there is space below your margin (since you're doing a block carve you will have a bunch of excess all over) that can be filled with flowable acrylic during the reline. Make sure your temp is not majorly hyper before the reline* this is huge. Remove excess inside if it is until it fits close to the other teeth occlusally.
Make sure to make a vent somewhere (the occlusal or interproximals if you removed those during your initial trim) to allow excess acrylic to flow out. Remove as much flowing acrylic as possible before it sets especially from the occlusal before that becomes too hyper.

 

[Dr. Dai Phan]

Hi there,

If you got only 30, then you really need some good guidance on how to make a good temp in 15 minutes or less. Sit down with an instructor and ask him on how to do it correctly. Make sure that he shows you physically rather than verbal. Fabrication of a high quality temp is easy if you know of the proper steps. DP

 

[OhioDMD]

Hi there,

If you got only 30, then you really need some good guidance on how to make a good temp in 15 minutes or less. Sit down with an instructor and ask him on how to do it correctly. Make sure that he shows you physically rather than verbal. Fabrication of a high quality temp is easy if you know of the proper steps. DP

It's a piece of cake if you are shown and allowed to use the proper modern materials. Free handing and relining a methyl methacrylate crown is far from realistic.

Fortunately or unfortunately I went to school with GV Black and this is how I would approach your problem. Mix 3 times more material in a paper cup to the consistency of honey. Keep an eye on the surface. When the shine disappears from the surface make a ball big enough to cover the prep, extend slightly beyond the mesial and distal of the approximating teeth and high enough to record the occlusal surface of the occluding teeth. Place it on the prep and close the articulator. Take the remainder in the cup and make a ball. Manipulate the excess by hand until it starts to get warm. This is when you pick the temp off the the prep and set it aside (temp should still be pliable......wait too long and it will be locked into undercuts). After the material is fully set begin removing the xs. Take care not to touch the mesial and distal contacts and the margins. If you need to add. Make the same honey consistency mix. Paint monomer on the area and paint sufficient material to correct the fault and allow to fully cure (xs in you hand is hot and hard) before removing and finishing. Most of this excessive in futility is learning to manipulate the materials. Hope this helps.

 

[beeho]

That's too bad you don't get to use molds of any sort. I've always been allowed to use them.

Anyways, since I've never done it free hand, my guess would be as the 2nd person said: if once you pull off the temporary and the margins look bad/missing to a large extent, start a new one over. You'll just waste more time trying to repair and there's the increased risk of fracturing the temp when you're contouring (as you've already experienced this 🙁 )

 

[MattBiggar80]

unfortunately when the instructor comes they usually stay a max of 5 minutes. they say mix it, now put on the tooth, and then they say i'll come back in 5 minutes.. which is usually closer to 30 minutes. i start working on the tooth after it is hard (after the 5 minutes) and im basically doing the same bad habits.

in short, getting help with an instructor is not an option.

Hi there,

If you got only 30, then you really need some good guidance on how to make a good temp in 15 minutes or less. Sit down with an instructor and ask him on how to do it correctly. Make sure that he shows you physically rather than verbal. Fabrication of a high quality temp is easy if you know of the proper steps. DP

 

[Dr. Dai Phan]

unfortunately when the instructor comes they usually stay a max of 5 minutes. they say mix it, now put on the tooth, and then they say i'll come back in 5 minutes.. which is usually closer to 30 minutes. i start working on the tooth after it is hard (after the 5 minutes) and im basically doing the same bad habits.

in short, getting help with an instructor is not an option.

Hi there,

I wish I could be there to help you but since I can't, let me try in writting:

1. First, make sure the prep is acceptable with adequate occlusal reduction. That means no knife edge anywhere and a shoulder or chamfer should be well defined all around. If you have a poor margin (too thin), then the temp material will not have enough thickness to withtand the rigors of trimming and polishing. If there is not enough occlusal reduction, again the temp material will be too thin and you will perforate when you do occlusal adjustments.

2. Make sure the temp matrix encompasses the whole prep and see if you enough occlusal clearance. A minimum of 1.0 mm is needed.

3. Lubricate the prep.

4. Mix the acrylic until a wet consistency is achieved. Then let it sit until the shine is gone on the surface and load into the matrix. Check to see if there are any voids and if so, pick the hole with a perio probe and load more acrylic in the area.

5. Seat the matrix onto the prep and pull up after 5 seconds. Look to make sure the margins of the prep is fully captured in the acrylic. If not, repeat step 4. If the acrylic is stuck to the prep, either the mix is too thin or not enough lubrication.

6. Let it set then remove and start trimming. Use a straight acrylic bur to trim the margin. Use your loups to make sure you do not cut into the margin.

7. Check you occlusion and then pumice the temp.

If done correctly, salt and pepper method is rarely employed. If you struggle, you need to have the faculty sit down and show you.Constant struggling means there is a serious break down either in teaching or learning method. DP

 

[Daurang]

Unfortunately it's impossible to tell you how to do it. You need to have one of the faculties show you in person. And just keep practicing and practicing so you become better with manipulating the material.