crown and bridge labwork

[mrlantern]

Is it just me or is it very common to adjust crown/bridge contacts and occlusion prior to cementing?

I never had problems with seating crowns in dental school or residency. But ever since I landed in private practice, I get back labwork that wouldn't seat all the way if I didn't trim off the contacts ( very time consuming because you don't want open contacts either ) and would have high occlusal surfaces. Some crowns even come with margins that you can pick at with the tine of an explorer but explorer tip thankfully wouldn't go all the way in. ( not sure if this qualifies as open margins )

Is this the fault of the lab or my clinical skills?

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[tinman831]

Is it just me or is it very common to adjust crown/bridge contacts and occlusion prior to cementing?

I never had problems with seating crowns in dental school or residency. But ever since I landed in private practice, I get back labwork that wouldn't seat all the way if I didn't trim off the contacts ( very time consuming because you don't want open contacts either ) and would have high occlusal surfaces. Some crowns even come with margins that you can pick at with the tine of an explorer but explorer tip thankfully wouldn't go all the way in. ( not sure if this qualifies as open margins )

Is this the fault of the lab or my clinical skills?

Granted I am still only a dental student, but I have yet to deliver a crown that has inserted perfectly, without any proximal or occlusal adjustments. There could be a number of factors that come into play, from fabricating the crown labside to impression taking chairside. It's probably safe to say that you will need to do some adjustment with every crown you get back. If you don't think that it's anything on your end, maybe you should try a different lab for your next few cases and see how those turn out.

 

[aphistis]

I'll get maybe one crown out of ten that just drops perfectly into place without requiring any adjustment. At the other end, maybe another one out of ten that I have to significantly adjust proximal contact or occlusion. The remainder are pretty close, but require just a few seconds' tweaking with a bur in order to get things right.

I prefer it this way. I'd rather have a lab whose crowns are normally slightly tight on interproximal contact. That way if a crown isn't built out quite as much for some reason, you end up with a *normal* contact that still works just fine. If your lab normally tries for ideal contact but comes up a touch short, now you've got an open contact and there's no option but to remake the crown.

 

[mrlantern]

How do you know if the margins are "adequate" enough? I noticed that crowns regularly have open margins if you were to look hard enough.

What are your minimum standards for closed margins? Do you also take pre-cementation BW xrays to confirm interproximal margins?

 

[mike3kgt]

Granted I am still only a dental student, but I have yet to deliver a crown that has inserted perfectly, without any proximal or occlusal adjustments. There could be a number of factors that come into play, from fabricating the crown labside to impression taking chairside. It's probably safe to say that you will need to do some adjustment with every crown you get back. If you don't think that it's anything on your end, maybe you should try a different lab for your next few cases and see how those turn out.

You are correct but you can do cases with labs that need no adjustments. If you have a good lab that knows you and your work/margins/occlusal philosophies, you can get very predictable crowns. Many times I have "dropped" in a crown and literally had no adjustments at all. The only instrument I would have to pick up was an explorer or scaler (for cement).

A lot depends on the lab you use, your prep, impression, and provisional. If you prep clean w/ minimal to no undercuts and have sharp margins, make good impressions, and have your assistant (or you!) making great provisionals with good contacts and occlusion not too tight or light and sending to a decent lab, you will get good results. You can get great results with full arch custom tray impressions, a semi-adjustable articulator and acrylic provisionals but you can also get good results with a triple tray, a hinge articulator and resin-based material provisionals.

I have tried many different things in practice but going the extra distance with the aformentioned gives you and your patient more confidence in your work. Having to adjust crowns for 30 minutes gives the patient the allusion that you "are grinding away my beautiful tooth."

Personally, I prefer full arch PVS in a stock tray, mounted on a semi-adjustable articulator, and acrylic provisionals sending to a good lab (~$175-250 unit).

It all comes with experience and that will come with time.

 

[aphistis]

How do you know if the margins are "adequate" enough? I noticed that crowns regularly have open margins if you were to look hard enough.

They shouldn't. Is marginal integrity the first thing you check when you seat a crown? If it is, you're doing it wrong. Tight interproximal contacts will give the false impression that occlusion is high and margins are open.

What are your minimum standards for closed margins? Do you also take pre-cementation BW xrays to confirm interproximal margins?

Once floss snaps cleanly through the contact, I use my eyes and an explorer. If they're happy, I'm happy.

X-rays for checking interproximal contact? No way. That's why God invented floss. The only time I shoot films for a crown is before I cement it to the abutment which is attached (also w/radiographic confirmation) to an implant.

 

[NAVY DDS 2010]

Is it just me or is it very common to adjust crown/bridge contacts and occlusion prior to cementing?

I never had problems with seating crowns in dental school or residency. But ever since I landed in private practice, I get back labwork that wouldn't seat all the way if I didn't trim off the contacts ( very time consuming because you don't want open contacts either ) and would have high occlusal surfaces. Some crowns even come with margins that you can pick at with the tine of an explorer but explorer tip thankfully wouldn't go all the way in. ( not sure if this qualifies as open margins )

Is this the fault of the lab or my clinical skills?

My question for you is why are you adjusting the occlusion before cemetation? Interproximally, if it comes from the lab with a bulky and tight contact, of course you would adjust it until it fits appropriately. But occlussally, why adjust before you have cemented. Depending on how well you have seated the crown or how much cemet you placed in the crown, the height of the occlusion may change. plus, it may not be 100% stable before cemetation and could rock slightly when adjusting and when checking occlusion. You won't get a fully accurrate reading until cemented.

Now, I am not trying to be argumentative here, but I really would like to know what dental school you attended. You are constantly asking questions clarifying how to perform fairly basic dental procedures. I would like to know what school you attended to see if it is you or if it is the school that has failed you. No wonder why you are struggling in your practice and are seriously considering leaving the profession. Based on what I have seen from your posts, if I were in your shoes I'd be very frustrated with being a dentist as well. It is actually concerning to me that a school would inadequately prepare you for practicing dentistry as it seems your school has in your case.

 

[mrlantern]

They shouldn't. Is marginal integrity the first thing you check when you seat a crown? If it is, you're doing it wrong. Tight interproximal contacts will give the false impression that occlusion is high and margins are open.


Once floss snaps cleanly through the contact, I use my eyes and an explorer. If they're happy, I'm happy.

X-rays for checking interproximal contact? No way. That's why God invented floss. The only time I shoot films for a crown is before I cement it to the abutment which is attached (also w/radiographic confirmation) to an implant.

I never said I check the margins as the first thing when trying in a crown. It just appears to me that some crowns appear to have greater marginal seal on one side versus another, where you can slightly pick at with an explorer. I was just wondering what everyone's standard was when it comes to checking crown margins.

And I never asked about taking BW xrays for checking interproximal contacts. I was asking about taking BW xrays for checking interproximal margins. Assuming there are nearby teeth, you can't deny that you can discover open interproximal margins only on BW xrays.

 

[mrlantern]

My question for you is why are you adjusting the occlusion before cemetation? Interproximally, if it comes from the lab with a bulky and tight contact, of course you would adjust it until it fits appropriately. But occlussally, why adjust before you have cemented. Depending on how well you have seated the crown or how much cemet you placed in the crown, the height of the occlusion may change. plus, it may not be 100% stable before cemetation and could rock slightly when adjusting and when checking occlusion. You won't get a fully accurrate reading until cemented.

Now, I am not trying to be argumentative here, but I really would like to know what dental school you attended. You are constantly asking questions clarifying how to perform fairly basic dental procedures. I would like to know what school you attended to see if it is you or if it is the school that has failed you. No wonder why you are struggling in your practice and are seriously considering leaving the profession. Based on what I have seen from your posts, if I were in your shoes I'd be very frustrated with being a dentist as well. It is actually concerning to me that a school would inadequately prepare you for practicing dentistry as it seems your school has in your case.

In school, I never received back a crown that required any adjustments. They all seated perfectly and I always had faculty clearance before cementationt.

In private practice, I'm just finding it unbelievable that it takes me 30 minutes - 1 hour to seat a crown or bridge. I find it manually difficult to check contacts without the crown being cemented. It's just as difficult to trim off excess interprox sides without creating open contacts.

 

[tinman831]

X-rays for checking interproximal contact? No way. That's why God invented floss. The only time I shoot films for a crown is before I cement it to the abutment which is attached (also w/radiographic confirmation) to an implant.

I think he means using BW's to check the margins interproximally to make sure it's being seated all the way. This is how we are taught to do it here at school.

 

[aphistis]

I never said I check the margins as the first thing when trying in a crown. It just appears to me that some crowns appear to have greater marginal seal on one side versus another, where you can slightly pick at with an explorer. I was just wondering what everyone's standard was when it comes to checking crown margins.

And I never asked about taking BW xrays for checking interproximal contacts. I was asking about taking BW xrays for checking interproximal margins. Assuming there are nearby teeth, you can't deny that you can discover open interproximal margins only on BW xrays.

Nope, I've never found it necessary. If you prepared the tooth properly, you should be able to fit an explorer tip interproximally. If you can't, you need to open the proximal contact more.

 

[OceanDMD]

My question for you is why are you adjusting the occlusion before cemetation? Interproximally, if it comes from the lab with a bulky and tight contact, of course you would adjust it until it fits appropriately. But occlussally, why adjust before you have cemented. Depending on how well you have seated the crown or how much cemet you placed in the crown, the height of the occlusion may change. plus, it may not be 100% stable before cemetation and could rock slightly when adjusting and when checking occlusion. You won't get a fully accurrate reading until cemented.

Now, I am not trying to be argumentative here, but I really would like to know what dental school you attended. You are constantly asking questions clarifying how to perform fairly basic dental procedures. I would like to know what school you attended to see if it is you or if it is the school that has failed you. No wonder why you are struggling in your practice and are seriously considering leaving the profession. Based on what I have seen from your posts, if I were in your shoes I'd be very frustrated with being a dentist as well. It is actually concerning to me that a school would inadequately prepare you for practicing dentistry as it seems your school has in your case.

The lab (and you should have in dental school) places die spacer on the die during the fabrication of the crown. This provides the assumed space for cement. When you seat a crown, you maintain marginal integrity. There should be NO SIGNIFICANT CHANGE IN OCCLUSION before or after cementation. If all of a sudden the crown is high, you fff up and now have an open margin. You have to adjust the occlusion (at least get it close) before cementation. The only time I dont is when Im seating inlays, onlays, or veneers. Think of this scenario, you cement your crown (without adjusting the bite) and the patient bites down and its like 2mm high (either you underprepared or the lab messed up the mount). Now you grind on this thing and the next thing you know you are through the porcelain and looking at metal. Now what? You are cutting that damn thing off and remaking it (unless its 2 or 15 ).

As far as the mrlantern goes, I am also confused about some of these questions you are asking as a practicing dentist (post/core in prior thread). If your preparation is good, impression clear, and lab prescription correct, unless the lab sucks there should be minimal adjustments. Good labs will send you a form where you tell them what trends you want with your cases. I personally have the lab go slightly heavy on all my contacts (so nothing is ever open like aphistis stated) and slightly light on my occlusion (because most labs tend to be heavy anyway). As far as margins, if your explorer gets between the crown margin and the prep margin its open. Would you want that cemented in your mouth?

 

[tinman831]

As far as margins, if your explorer gets between the crown margin and the prep margin its open. Would you want that cemented in your mouth?

Now lets say, you have a step, from the margin of the crown, to the actual tooth structure. Margins are sealed, just not flush with the tooth. Do you go ahead and cement or send back to the lab?

 

[OceanDMD]

Now lets say, you have a step, from the margin of the crown, to the actual tooth structure. Margins are sealed, just not flush with the tooth. Do you go ahead and cement or send back to the lab?

If you are referring to an overhang, I would seat the crown and go in with a flame diamond to polish the margin flush. Kind of like the cementation technique with those piece of shat Lumineers.

 

[teeth63a]

Now lets say, you have a step, from the margin of the crown, to the actual tooth structure. Margins are sealed, just not flush with the tooth. Do you go ahead and cement or send back to the lab?

This is an undercontouring of the crown, where there is not enough bulk on the buccal or lingual surface to be flush with the tooth. Although this is not ideal, since plaque can rest on the step, the margin is sealed which is more important. I (and most dentists) have no problem cementing this in, esp if the patient has good hygiene.

The only real send back cases are open margins or open proximal contacts.

 

[teeth63a]

Is it just me or is it very common to adjust crown/bridge contacts and occlusion prior to cementing?

I never had problems with seating crowns in dental school or residency. But ever since I landed in private practice, I get back labwork that wouldn't seat all the way if I didn't trim off the contacts ( very time consuming because you don't want open contacts either ) and would have high occlusal surfaces. Some crowns even come with margins that you can pick at with the tine of an explorer but explorer tip thankfully wouldn't go all the way in. ( not sure if this qualifies as open margins )

Is this the fault of the lab or my clinical skills?

The standard taught at the greatest dental school (Pacific )

CIMO

remove temp, scale and pumice tooth.
check following
Contact - check contact with floss
Internal - check internal fit with Occlude spray or similar
Margin - check margin with explorer, take BWX to verify prox. margin.
Occlusal - check occlusion

I'm sure we all learned the same.

What you're learning in private practice is that not all labs tech do the same work. If your work is going to an offshore lab (like China), expect problems with cementation. I've tried two different chinese labs (as a cost control matter) and was NEVER happy with the results...open margins due to poor internal fit, or good internal fit but 1 mm open margin (miscut die). I think its due to transport or deformation of pvs, or pure techincal error on the lab's side. My point is that your lab may be less than stellar.

You need to find a good lab and see how they work, and communicate your preferences to them. I ask for normal proximal contacts with light occlusal contacts for single unit crowns. A previous lab I used to work with consistently made heavier contacts than I wanted, so I always requested light proximal contacts. I choose light occlusal contacts to minimize the amount of time I spend grinding at the occlusal surface.

I can honestly say that I cement maybe about 5 out of 10 without adjustment, and 4 requiring minor adjustment (less than 10 minutes), and 1 requiring major adjustment (for whatever reason).

So my amended cementation procedure is:
check contact
check margin and verify with BWX
pt verifies he likes esthetics
cement
check occlusion

I check occlusion last and cemented so that 1) pt can never swallow during inserting and removing repeatedly and 2) it doesn't go up the high speed vac. With a bridge, I check the occlusion first before cementation.

The one caveat to this is the lab can take only so much responsibility...a good crown comes from a good impression. If you're not properly isolating the tooth or send them an impression with void on the margins (you can live with voids everywhere else), expect a crappy crown. It takes time, but I double cord, isolate with rools, use viscostat (preferably clear, not the brown one) and whip out the electrosurge to control any bleeding the viscostat can't take care of.

 

[aphistis]

If you are referring to an overhang, I would seat the crown and go in with a flame diamond to polish the margin flush. Kind of like the cementation technique with those piece of shat Lumineers.

This is an undercontouring of the crown, where there is not enough bulk on the buccal or lingual surface to be flush with the tooth. Although this is not ideal, since plaque can rest on the step, the margin is sealed which is more important. I (and most dentists) have no problem cementing this in, esp if the patient has good hygiene.

The only real send back cases are open margins or open proximal contacts.

Agree with both of these. Overhangs bother me more than step-offs, but I'll cement either as long as I can smooth them off.

 

[mrlantern]

This just in. True story. I was supposed to deliver an anterior all-porcelain crown today. I removed the temp, cleaned off the residual cement, and tried on the permanent crown.

The crown would rock back and forth on the prep. Thinking it was the tight contacts, I repeatedly grinded off them off. The crown fit was still loose and kept rocking. Even after intentionally making open contacts, the crown would still rock back and forth and wouldn't stay in one stable position. I had to retake the final impression and return the crown back to the lab.

 

[DrJeff]

I'll get maybe one crown out of ten that just drops perfectly into place without requiring any adjustment. At the other end, maybe another one out of ten that I have to significantly adjust proximal contact or occlusion. The remainder are pretty close, but require just a few seconds' tweaking with a bur in order to get things right.

I prefer it this way. I'd rather have a lab whose crowns are normally slightly tight on interproximal contact. That way if a crown isn't built out quite as much for some reason, you end up with a *normal* contact that still works just fine. If your lab normally tries for ideal contact but comes up a touch short, now you've got an open contact and there's no option but to remake the crown.

Agree!

Most crowns that I cement will need just a quick, simple tweak to the interproximals or a slight contouring of a marginal ridge or centric stop. If it takes me more than say 1 minute to adjust a crown pre-cementing then either a) I took a cr@ppy impression/bite (the likely cause) or b) the lab tech was feeling a bit overzealous when layering the porcelain??

Always, always better to have a crown too tight interproximally when trying it in than tooo loose. Too tight = quick adjustment = you cement that day too loose = recement the temp and send it back to the lab for more porcelain to be added

 

[DrJeff]

This just in. True story. I was supposed to deliver an anterior all-porcelain crown today. I removed the temp, cleaned off the residual cement, and tried on the permanent crown.

The crown would rock back and forth on the prep. Thinking it was the tight contacts, I repeatedly grinded off them off. The crown fit was still loose and kept rocking. Even after intentionally making open contacts, the crown would still rock back and forth and wouldn't stay in one stable position. I had to retake the final impression and return the crown back to the lab.

Unfortunately this is a more common experience than 1 might think, and the majority of time the fault isn't with the lab tech, but with your impression taking Never really realized how many bad impressions get taken until I went to a CE course sponsored by and held at the lab where I send the majority of my crown and bridge to. The owner basically told us docs that were there to walk around the lab benches (especially in the "receiving area" where the impressions hadn't been poured yet) and actually look at the impressions . An eye opening experience to say the least.

And if you're giving the lab an innacurrate impression, that crown is more than likely going to have some issues inspite of the lab techs ability.

 

[armorshell]

Whoa whoa there teeth63a. I don't know who was teaching fixed at Pacific when you went here, but we went ahead and added an 'E' on the end of that bad boy. Now when I do a CIMOE, I make sure the patient finds the esthetics of their FVC acceptable.

 

[kiji talons]

This just in. True story. I was supposed to deliver an anterior all-porcelain crown today. I removed the temp, cleaned off the residual cement, and tried on the permanent crown.

The crown would rock back and forth on the prep. Thinking it was the tight contacts, I repeatedly grinded off them off. The crown fit was still loose and kept rocking. Even after intentionally making open contacts, the crown would still rock back and forth and wouldn't stay in one stable position. I had to retake the final impression and return the crown back to the lab.

i have only been out 2 years, and i must admit that your questions are things that i learned in school. where did you go to school. if the crown rocks, look at the prep. if you have undercuts you might have to re-prep. also, you might have a sharp line angle which can break off when they pour up the cast. if it looks sharp, get the patient numb and round off your prep. if it still doesn't seat, check it internally with occlude. if it still doesn't seat, re-take you impression.

 

[Lidopaine82]

Agree!

Most crowns that I cement will need just a quick, simple tweak to the interproximals or a slight contouring of a marginal ridge or centric stop. If it takes me more than say 1 minute to adjust a crown pre-cementing then either a) I took a cr@ppy impression/bite (the likely cause) or b) the lab tech was feeling a bit overzealous when layering the porcelain??

Always, always better to have a crown too tight interproximally when trying it in than tooo loose. Too tight = quick adjustment = you cement that day too loose = recement the temp and send it back to the lab for more porcelain to be added

Dr. Jeff, can you describe your technique for tweaking the interproximals?

 

[OceanDMD]

i have only been out 2 years, and i must admit that your questions are things that i learned in school. where did you go to school. if the crown rocks, look at the prep. if you have undercuts you might have to re-prep. also, you might have a sharp line angle which can break off when they pour up the cast. if it looks sharp, get the patient numb and round off your prep. if it still doesn't seat, check it internally with occlude. if it still doesn't seat, re-take you impression.

Good ideas here. The other thing I will do is take my temporary and try it on the die. If there is a big discrepany you know there is a big problem and likely a new impression.

 

[DrJeff]

Dr. Jeff, can you describe your technique for tweaking the interproximals?

Sure. nothing super radical though by any means.

#1 Double/Triple check that after she removed the temporary that my assistant cleaned ALL of the temporary cement off - you'd be surprised how many times a little remaining temporary cement can be the cause of seating problems

#2 Place a little fit checker (http://www.gcamerica.com/gcfitcheck2.html) on the inside of the crown and seat (or atleast attempt to seat )

#3 reguardless of if the crown does or doesn't fully seat, I check the contacts with a thin piece of shim stock and then finally a piece of floss.

Depending on what the fit checker shows or how the shim stock does/doesn't slide through the contact will determine whether I'm looking for a irregularity in the coping material or a contact to adjust

If I'm adjusting the inside of the coping based on a fit checker finding I'm either using a fine grit diamond bur or a green stone, If I'm adjusting a porcelain contact I use Brasseler's Dialite Ceramic polishing points/cones/discs (http://www.brasselerusa.com/products/polishdisplay.cfm?zoom=diamonds&id=1170) and If I'm adjusting a full gold crown I'm using a sof-flex disc.

After each adjustment it's back to the fit checker or shim stock (depending on where I adjusted) until fully seated.

Just before I'm ready for cement, I have my assistant take a quick PA to make sure that the crown(s) are fully seated, and then cement away.

 

[aphistis]

Sure. nothing super radical though by any means.

#1 Double/Triple check that after she removed the temporary that my assistant cleaned ALL of the temporary cement off - you'd be surprised how many times a little remaining temporary cement can be the cause of seating problems

#2 Place a little fit checker (http://www.gcamerica.com/gcfitcheck2.html) on the inside of the crown and seat (or atleast attempt to seat )

#3 reguardless of if the crown does or doesn't fully seat, I check the contacts with a thin piece of shim stock and then finally a piece of floss.

Depending on what the fit checker shows or how the shim stock does/doesn't slide through the contact will determine whether I'm looking for a irregularity in the coping material or a contact to adjust

If I'm adjusting the inside of the coping based on a fit checker finding I'm either using a fine grit diamond bur or a green stone, If I'm adjusting a porcelain contact I use Brasseler's Dialite Ceramic polishing points/cones/discs (http://www.brasselerusa.com/products/polishdisplay.cfm?zoom=diamonds&id=1170) and If I'm adjusting a full gold crown I'm using a sof-flex disc.

After each adjustment it's back to the fit checker or shim stock (depending on where I adjusted) until fully seated.

Just before I'm ready for cement, I have my assistant take a quick PA to make sure that the crown(s) are fully seated, and then cement away.

+1 for Fit Checker. Truly wonderful stuff. I also like Ocean's idea of trying the temporary onto the die. I'd never even thought of doing that before.