A question

[rose82]

How much time do dentists (working as an associate) get to do a molar crown prep in private practice?And how much time would be reasonable? Im going to start my first crown prep soon in dental school and although I'm not looking for the speed now,just needed a heads up.Thanks!

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[live]

I admire you wanting to get your speed up so early on, but focus more on learning the proper prep tech and how to do it intraorally without having to break your back or the patient's neck. This will lead to significant increases in speed later on. To answer your question though, we've been told that 45 minutes is a well respected time and very satisfactory (start to finish) to do a good crown prep, accurate final impression, and solid temporary as an associate. Good luck!

 

[bigbadaboom]

How much time do dentists (working as an associate) get to do a molar crown prep in private practice?And how much time would be reasonable? Im going to start my first crown prep soon in dental school and although I'm not looking for the speed now,just needed a heads up.Thanks!

As long as it takes to do a good prep and good impression and temporize it. I know a 20 year out of school dentist taking full 45 minutes just on the prep. I know of a recently retired dentist(25 years in practice) who books 1.5 hours appointment for a single crown prep appointment. I also know a classmate who claims to prep one in 3 minutes. I probably wouldn't want him to touch my tooth.

My first crown appointment in school took 2 hours, without impression. Just the prep, and making the temporary. I had to schedule another impression appointment.

Learn and do the things the right way, then pick up the speed later on. Don't book a 3 hour appointment, you and the patient will both get really tired. School is place to learn, don't rush it.

 

[Kam1]

At most dental offices, the associate chooses the amount of time (within reason) for various procedures. For a crown prep, I think around an hour is reasonable.

 

[rose82]

Thank you for the responses. I was not looking to be fast(just wanted to get a sense of how it is in the real world). I actually booked a 3 hr appointment for prep and temp without the impression. But do you guys take the impression at the same time as preparation? I thought the tissues should heal before taking an impression,so it is booked as a second appt. Is it not true?

 

[bigbadaboom]

yes the gingival tissue needs to be in good shape before taking an impression.
Get perio under control before the restoratives. You can take impression same day if they're not too traumatized.

I have been placing supragingival margin more often lately, and more conservatife gold onlays. No packing cords needed, plus clear margin on impression.

 

[live]

Gold onlays? Nice. Wish we did more of those here at my program and that more patients would go for them. You hear about how great they are and how long lasting they can be but I am not sure anyone in my class has done one yet (ceramics for sure but no gold). Did you get to do these in school or just decided on doing them once you got out?

 

[keeneye]

yes the gingival tissue needs to be in good shape before taking an impression.
Get perio under control before the restoratives. You can take impression same day if they're not too traumatized.

I have been placing supragingival margin more often lately, and more conservatife gold onlays. No packing cords needed, plus clear margin on impression.

what was the treatment plan that lead you to place supragingival margins. Also, what type of margin did you use and why?

 

[flapaTron]

dude keeneye your avatar is f***ing hilarious

 

[Mackchops]

I think it's impressive to be mindful of your time even when you're about to begin your first crown! Keep a mental note of how long it took and try to improve on that for the next one.

My 2 cents... You booked 3 hours for this one? Break it down -- begin drilling after 20 mins (seating, small talk, anesthesia, signatures, etc), contacts broken after another 15, occlusal reduction perfect another 10, margins perfect another 15. Then 1 hour for the temp. This is only 2 hours and if you can do it you've got plenty of time to take a good impression and cement the temp. If not, you've got some room to play with.

If it's a posterior tooth with solid tooth structure I like to keep supragingival margins -- easier to clean. If it's an anterior tooth I'll go at the gingiva or a little sub-g for esthetics. Try infiltating a little lido w/epi 360 if you're having problems keeping it dry. Nicely soaked hemodent cord -- use the 2 cord technique and leave the apical cord in. A good impression is all about good tissue management.

If you give yourself 3 hours to prep a tooth you'll take 3 hours. If you give yourself 1 hour, you'll take 1 hour. Push yourself. Plan ahead.

 

[bigbadaboom]

Gold onlays? Nice. Wish we did more of those here at my program and that more patients would go for them. You hear about how great they are and how long lasting they can be but I am not sure anyone in my class has done one yet (ceramics for sure but no gold). Did you get to do these in school or just decided on doing them once you got out?

actually learnt how to do gold onlays in school, had to do one in the pre-clinical lab.

i have seen many great gold onlays from this dentist who was in practice for 40+ years. Some of these in their mouth are older than me. I'm thoroughly impressed with how well this material holds up.

I have decided to do more of these gold restorations instead of PFM/PVC for the reason of less reduction on teeth structure. The margins on these restoration can be burnished in mouth if needed.
I do not propose them in more visible area of the mouth, like premolars or lower first molars.
Many times I think dentists assume patients do not want metal in their mouth and don't bother explaining to them the benefit of gold restorations.
I just cemented a gold onlay on a 30something female on a upper second molar. She was open to the idea after some good education. It saved her a lot of enamel.

Modern dental materials like eMax supposedly good too. I have had opportunity to work with a Cerec3D machine. You can't argue the long history of success with these metal crowns against less proven, more modern materials.
My gripe with Cerec machine owners is that many of the them see it as a big hammer, and everything they see looks like a nail, and forget they got other tools in their toolbox.

 

[bigbadaboom]

what was the treatment plan that lead you to place supragingival margins. Also, what type of margin did you use and why?

supragingival margin gives patient easy access to keep them clean. Of course it's not desirable in more visible area of the mouth, like anterior facial area.

for full gold it's bevel margin so you can burnish it.
for porcelain fused to metal, it's more difficult with a bevel or feather joint margin since during the porcelain firing these margin may be distorted. Chamfer margin for most of my pfm.

 

[rose82]

Thank you Bigbadaboom and specially Mackchops.I liked your breakdown and although I'm not sure if I can follow that now, I will surely keep it in mind and try to tune myself to timing slowly. I've heard horrible stories where you are under constant pressure when you work as an associate.

 

[keeneye]

dude keeneye your avatar is f***ing hilarious

I knew immediately that would be my avatar. I have a couple good ones,

search these in google image:

1. "google image molar"
2. "molar bear"


but, for this page, I pose a question. Who thinks bevels are obsolete?

 

[Mackchops]

but, for this page, I pose a question. Who thinks bevels are obsolete?

*raises his hand

What's the rationale for bevels? Better seal due to angles and reduced restoration/tooth interface width? False. Bacteria are smaller than even the best-sealed margin...

 

[flapaTron]

*raises his hand

What's the rationale for bevels? Better seal due to angles and reduced restoration/tooth interface width? False. Bacteria are smaller than even the best-sealed margin...

gives me a reason to bust out the flame burs once in a while.

 

[Mackchops]

gives me a reason to bust out the flame burs once in a while.

You could always use your flame bur to drill your initials onto the occlusal surface of your prep! Sign your work 🙂

 

[rose82]

*raises his hand

What's the rationale for bevels? Better seal due to angles and reduced restoration/tooth interface width? False. Bacteria are smaller than even the best-sealed margin...

So are you against putting a bevel?One of my professor puts a 1 mm bevel and his crowns last for life. I have personally assisted a dentist and seen what a bevel can do for a gold crown.

 

[mike3kgt]

Depends on what you call adding a "bevel":

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J Prosthet Dent. 1981 Feb;45(2):138-45.
The effect of various finish line preparations on the marginal seal and occlusal seat of full crown preparations.
Gavelis JR, Morency JD, Riley ED, Sozio RB.
Abstract

The influences of the marginal design of a full crown on the occlusal seat and marginal seal of a cemented full crown restoration was examined. Under the conditions of the study, the featheredge and parallel bevel preparations demonstrated the best marginal seal, followed in order by the full shoulder, 45-degree shoulder, and finally the 90-degree shoulders with 30-degree and 45-degree bevels. With regard to seating of the restoration, the 90-degree full shoulder demonstrated the best seat, followed in order by the 45-degree shoulder, 90-degree shoulder with 45-degree bevel, featheredge, 90-degree shoulder with 30-degree bevel, chamfer with parallel bevel, and finally 90-degree shoulder with parallel bevel.

 

[Mackchops]

... published in 1981...

My point is that look at the feather edge margin and its pack-leading 31 micrometer seal. Now look up the diameter of an S. mutans bacterium. Still think there's ever going to be such a thing as a marginal "seal"?

Add in the fact that you get better seating and an easier lab-fab of bevel-less crowns and I personally choose not to bevel. Throw in the huge increase in all-ceramic restorations, which hopefully nobody would suggest beveling the prep for, and it seems to me that bevels are passe.

Depends on what you call adding a "bevel":

-------

J Prosthet Dent. 1981 Feb;45(2):138-45.
The effect of various finish line preparations on the marginal seal and occlusal seat of full crown preparations.
Gavelis JR, Morency JD, Riley ED, Sozio RB.
Abstract

The influences of the marginal design of a full crown on the occlusal seat and marginal seal of a cemented full crown restoration was examined. Under the conditions of the study, the featheredge and parallel bevel preparations demonstrated the best marginal seal, followed in order by the full shoulder, 45-degree shoulder, and finally the 90-degree shoulders with 30-degree and 45-degree bevels. With regard to seating of the restoration, the 90-degree full shoulder demonstrated the best seat, followed in order by the 45-degree shoulder, 90-degree shoulder with 45-degree bevel, featheredge, 90-degree shoulder with 30-degree bevel, chamfer with parallel bevel, and finally 90-degree shoulder with parallel bevel.

 

[Mackchops]

So are you against putting a bevel?One of my professor puts a 1 mm bevel and his crowns last for life. I have personally assisted a dentist and seen what a bevel can do for a gold crown.

One of my professors used a flame bur to perform "intrasulcular crown-lengthening"... doesn't mean it should be done!

That said, different techniques work differently for different clinicians! Use what works in your hands... EBD only goes so far!