Open Margin on Crown

[HatInTheCat]

Hello! I recently cemented a zirconia crown on tooth #18. Tooth has a retention groove on the facial due to a short clinical crown. Upon trying in the crown, determined the marginal fit was satisfactory. However, upon cementing, i think the insertion was offset by the retention groove on the buccal and caused an open margin on the buccal detected clinically and radiographically. Next day, I contacted the patient to do post op check, pt experienced some sensitivity to cold. Would like some opinions on remedying the issue. My thoughts are to present the patient with the option of redoing the crown or sealing the open margin with RMGI. Opinions? P.S.--I probably will NEVER cut a retention groove ever again!

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[knewstance]

Retention grooves aren't always a bad idea. With crowns that have a unique path of insertion, I like to practice putting them on a few times before I go in with cement.

It sounds like you need to redo the crown for this patient if it has an open margin both radiographically and clinically. I learned to check my margin clinically right after seating the crown, before any curing or anything to prevent this.

 

[TanMan]

Hello! I recently cemented a zirconia crown on tooth #18. Tooth has a retention groove on the facial due to a short clinical crown. Upon trying in the crown, determined the marginal fit was satisfactory. However, upon cementing, i think the insertion was offset by the retention groove on the buccal and caused an open margin on the buccal detected clinically and radiographically. Next day, I contacted the patient to do post op check, pt experienced some sensitivity to cold. Would like some opinions on remedying the issue. My thoughts are to present the patient with the option of redoing the crown or sealing the open margin with RMGI. Opinions? P.S.--I probably will NEVER cut a retention groove ever again!

You gotta look at the risk v. benefit of redoing the crown. If your patient is experiencing reversible pulpitis and the prep was close to the pulp, redoing the crown may not be the best course of action as you might end up pushing the tooth towards symptomatic irreversible pulpitis. Test where the cold sensitivity is coming from. If it's from the open margin, then you got two options: either redo the crown or seal with bond/rmgi in the meanwhile. What to do would depend on the aggressiveness of your prep and pulpal diagnosis. If you think you're teetering on irreversible pulpitis and don't want to do an endo, then do the more conservative patch first. If symptoms go away, then you can either leave it be or redo the crown. If symptoms don't go away, either redo the crown and/or root canal the tooth depending on pulpal diagnosis.

From my experience, retention grooves on zirconia crowns tend to be less retentive than other crowns (emax, PFM,cast) due to shrinkage that occurs from the sintering process. I don't like retention grooves, but you can always try to bond zirconia. However, bonded zirconia is a PITA to remove, if you ever have to remove it. Typically, on the height of contours of a mandibular second molar, I prefer retention grooves on the mesial and distal, since it provides a counter towards the buccal and lingual slopes.

 

[oralcare123]

Redo. No questions

 

[schmoob]

Like @TanMan said, place single unit crown retention grooves on the Mesial and distal. Buccal and lingual retention grooves are better suited for bridges.

 

[2TH MVR]

You gotta look at the risk v. benefit of redoing the crown.

There's an unfortunate operator bias that exists in the real world vs. a teaching facility. For the dentist .... there is no "financial" benefit of redoing the crown. The open margin is operator and/or lab error regardless of the pulpal diagnosis.

Curious how many "patches" are done in the real world. Do they actually work longterm?

I was talking to a managing dentist at the Corp I work at. He told me that he had to take post crown seatment xrays to determine margin integrity, get credit for the crown, and for the insurance company. I might have misinterpreted him.

 

[TanMan]

There's an unfortunate operator bias that exists in the real world vs. a teaching facility. For the dentist .... there is no "financial" benefit of redoing the crown. The open margin is operator and/or lab error regardless of the pulpal diagnosis.

Curious how many "patches" are done in the real world. Do they actually work longterm?

I was talking to a managing dentist at the Corp I work at. He told me that he had to take post crown seatment xrays to determine margin integrity, get credit for the crown, and for the insurance company. I might have misinterpreted him.

The financial benefit of redoing a crown successfully without symptoms is getting a returning patient w/ potentially more work in the future. If you redo a crown and it hurts even more + have to do endo, you are more likely to have issues with that patient and patient retention as well. When I get new patients that present with open margins + symptomatic, you have to be realistic that there's risk of an endo. The advantage the OP has here is that he/she knows how aggressive the prep/caries was, pulp status, proximity to pulp, and so on... We often don't have that with new patients, and PFM's/zirconia make it worse to know what's going on in there. Always plan for the worst case scenario. Alluding to OP's situation, if it seated fully on try-in, but didn't afterwards, it's either path of insertion or cement setting too fast. If you had an er:yag laser, you could pop the crown right off.

Your managing dentist is correct. You need postop radiographs to determine integrity, but more importantly, get paid by insurances and be ready for an audit. Also take postop cementation photos to be safe. Emax crowns are not very forgiving on the radiographs; they look terrible. Zirconia crowns look better radiographically.

 

[HatInTheCat]

Good advice. Thanks for the input! Will follow up in due time.