This is just a quick tip that can speed up your crown prep appointments.
Most crown preps involve teeth that already have large amalgams. Personally, I take out all old restorative materials, clean up the tooth, and do a build-up. I don’t like leaving behind or covering up old amalgam. And, I’m always amazed at how much decay I find hiding under those old amalgams, not to mention the old Dycal “cottage cheese” sludge.
I like an “ideal” crown prep form in terms of retention and resistance form. Remember those terms from dental school? Some of what we learned still applies today.
But, many of us are still doing the steps in the same order as we were taught in dental school. We were taught to first take out all the old amalgam. Clean up any decay or other “schmutz.” Then slap a matrix band on and build-up with composite. THEN start the crown prep. Sure… this works just fine. But, have you ever gotten done with the crown prep and found that there was very little build-up left or sometimes NONE?? Aaaargh! I spent all that time building it up, only to have little to none left after the prep???
Here’s a different approach. Prep the tooth FIRST! That is… do the “rough” crown prep, first. By that, I mean don’t take out the old amalgam. Just prep the tooth as if it was a crown prep on a virgin tooth. Do the occlusal and axial reduction first. Oh… and if you want it to go quickly, try doing it with a “metal cutting” bur like Brasseler’s H34L bur.
Tooth #29 has deep abfraction and large amalgam. Tx plan: Crown
This is the H34-L bur from Brasseler. It's made to cut metal. But, it will go through enamel like butter and works well for the "rough" prep.
When you’re done, you’ll have what I call a “rough” prep. And, you may find that almost all the old amalgam is already gone.
Here is the "rough" prep. Some old amalgam remains.
If there is any old restorative material left, now is the time to remove it and clean up the “schmutz.”
"Rough" prep now with remaining amalgam removed.
Once you’re down to clean dentin, you may find that all you need to do is a little “block out” with composite. The point is that you will likely be able to free-hand a bit of composite for the build-up. And, it won’t take nearly as long as the dental school method.
Once you’ve done your build-up or block-out, you can then use your typical diamonds to refine your crown prep. Presto! Done! Ready for impression!
Composite build-up placed and final prep. Laser troughing for impression.
Final impression (Impregum).
Efficiency while not sacrificing quality… even better… INCREASING quality and lowering stress is the Dental Warrior way!
PS… Some related posts you may find interesting:
- Picasso Lite – It’s time to pull the trigger on a diode laser!
- 3M ESPE’s Disposable Intra-oral Impression Syringe – Product Review
- Optragate for Full Arch Prep & Impression
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Great minds think alike!
Thanks for checking in, Vic!
Mike, this is one of the best tricks I picked up from you years ago. I was fresh out of school and new to Dentaltown. It is something I’ve passed on to many other dental friends over the years. Between this and using a wheel diamond for my occlusal reduction my crown prep times were really cut down!
Very cool, Nat! It was one of those forehead-smacking moments for me. 🙂
Great tip and good luck with the Blog. I will check back often.
So, what’s the deal with the Impregum? I thought you were a hard core H&H/HAIT user.
Hi Brad!
I was a long-time H&H guy. Still use it some. But, recently I visited 3M up in Minnesota and they successfully convinced me to try good ol’ Impregum. Combined with my new Picasso Lite laser (blog coming on that), I get some pretty awesome impressions.
I cant get away from aquasil, when used with their “B4” surfacant I really cant beat the impressions. But to each their own. Mike u Rock
Very nice pictures !
What camera do you use ?
I use a DSLR. Doesn’t really matter which. You need a macro lens and ring flash. Then you also need a quality front-surface photographic mirror. But for what it’s worth, these photos were taken with a Canon Rebel XSI.
Me Likey!! Great tip Mike!
I can’t believe this post is currently the 3rd most popular!
I have a crazy question! I just started workink for this new dentist and i am not impressed with her work. Im only a dental assistant but I feel I’ve seen enough to know what looks good and what doesnt. Today we had a patient coming in for a post&core and crown. Well, the dentist says she doesnt do post and cores so today she will only do the crown. I asked her what about the post and core. She said the patient can come back and the other dentist there will do it. So we removed the temp filling, put a new cotton pellet in, built the tooth up with a resin composite then took the final impression and sent to the lab. So the patient is coming back in 2 days so the other dentist can place the post and core. We did this on tooth #20 and tooth #15. Im confused…. this just sound backwards! I just need an opinion from someone who is more experienced then me.
Hi Beth,
Of course, it’s impossible for me to really draw any conclusions or render any solid opinion without seeing the case for myself. It sounds like you are in a group / corporate practice (another dentist taking over the case at the next visit?). I’ve never done it as you have described. And, putting a cotton pellet under a build-up is unusual – again as you have described it. But, I can’t be sure what the dentist is planning in the future for the tooth.
You could certainly ask for an explanation from the dentist (privately – not with the patient in the room).
It’s not the question that’s crazy, it’s your dentist that’s crazy.
The dentist “doesn’t do post and cores”. What?
That’s like saying the dentist doesn’t do dentistry.
The post and/or core is the foundation of a good crown.
A cotton pellet doesn’t qualify and neither does carrying out the whole procedure back to front. Get out of there fast and find someone competent.
When I had crown procedures in the past, there was some chemical prep prior to gluing the finished crown. I would get a strong acid taste; phosphoric? The dentist I’m seeing now just wipes the “stump” and places the crown. Could this invite decay on the remaining tooth structure? Also, she did not cement the temporary and it came off so often I bought some fixodent. Sorry to bother you with this, but I could find no patient-oriented blog.
I have a similar question to falk burger
Placing either a temporary or permanent crown without cement is a virtual guarantee of inflammation of both the living tooth and the surrounding soft tissues followed thereafter by decay and gum problems.
It amounts to negligence and is indefensible.
I’m not really in a position to comment on treatment by other dentists without having all the information available to me or seeing you in person.
I did a search for “ask the dentist.” There are a number of websites oriented to consumers.
Well , Many years ago I found a trick in operative dentistry journal may be 1975 issue. for crown prep start with a round bur . push it halfway in free gingiva cut the finishing line circumferentialy at an angle of 45 degrees. the shank wont let you go deep. Then cut the remaining of the tooth .If you ask me I,ll tell you what size of bur to use . Dr.Farzin
That must have been a well done amalgam to start with to last till the end of your crown preparation !! I am a Prosthodontist and I still enjoyed reading the article, thanks for sharing.
hi
i am an oral surgeon n now i am starting to practice general dentistry, when i am practicing crown prep my finish line seems lost in some areas n also i find it difficult to break the contacts without damagin adjacent tooth
Hi Reshma!
Thanks for visiting my blog! I’ve always found breaking the contacts the most tedious part of crown preps. And, I’m very particular about not touching / damaging the adjacent proximal teeth. There are a few tricks. First, get a sharp / new bur. You can even use a cross-cut carbide. You can then cut from the top down. That is… go to the INSIDE of the marginal ridge and work your way down, leaving about a millimeter of tooth between the bur and the next tooth. When you’re done (down to below the contact), you’ll have a “slice of tooth” that will simply fall off.
There’s a nifty tool from Ultradent called the “Intergard.” It looks like a thick segmental piece of metal matrix band. Stick that between the teeth and prep away without worries about nicking the adjacent tooth.
I hope that made sense and helps!
When I do crown prep I usually get undercut and it takes me long time to remove undercut from the prepared tooth. Can give me some tips to do crown prep without having undercut in first place.
Hi Tahrima!
Are the undercuts the result of removing caries or old restorations? Or are the undercuts the result of improper handpiece / bur angulation?
The undercuts I get during crown prep are possibly result of improper handpiece/ bur angulation.
Well you have answered your own question haven’t you?
I suggest you do a lot of training and practice on extracted teeth before mutilating a patient’s teeth.
Great technique… Thank you for sharing!!
Also, I have a question. I have a patient with fractured upper lateral. It’s fractured at gingival level but tooth doesn’t not require root canal. What are my best options for restoring it? Also for a crown options what will be my Crown prep. Appreciate your opinion!!
Hi K,
It’s difficult to give an answer without seeing an x-ray and a photo. It depends. But, I have done RCTs on vital teeth for restorative purposes.
This is a case from two years ago… Rugby player fractured off an existing crown (tooth #7) with the coronal tooth structure inside. I performed root canal therapy, placed a post and core, and then prepped for a new crown. Patient refused crown-lengthening surgery, so I prepped it as far as I could to get a bit of “ferrule” and margin on dentin. The third photo is the temporary crown. This same patient came in 2 weeks ago after fracturing the OTHER lateral (#10). The restoration of #7 from two years ago is intact.
Thank you for the reply!! Well clinically it’s same as the first pic( your case).
In a case like this where it’s fractured to the gingival level it’s best to do elective RCT. But What is your opinion on just doing a flat surface prep and doing ceramic crown and not do RCT? Might be a dumb question I know!!
Personally, I wouldn’t trust it without the post in such a case. Even with a post, longevity is questionable, and I let patients know about it. The other option is extraction and an implant.
My Professor told me to do it this way, I had no idea why for a while as he is a little cryptic sometimes but a generally nice guy.
Problem is nobody else does it this way at uni so whenever I see the patient with someone else I have to explain the whole situation over again.
Can’t wait to get out of uni.
Hang in there, Dave! The real learning happens after you graduate. And, that’s what makes it fun!
Thanks for visiting my blog!
Like so many professors, he is an idiot.
There is no such thing as a “flat surface crown prep”. Has no one taught you about resistance and retention form? In a situation like there is neither and the result is just a failure waiting to happen.
Hey Belinda, you know the sound a cork makes when it is pulled out of a bottle of wine? Listen for that sound closely as it will indicate to you when you have sufficiently pulled your head out of your ass. Take your vitriol and holier-than-thou opinions somewhere else.
I like your technique, but at the same time do the opposite.
I am a firm believer that natural tooth material comes first, then a long time nothing and then finally dental materials.
That means that I remove as little -supported- tooth material as possible.
In this case I would replace the amalgam, perhaps at the same time covering the cusps.
I only recently left restoring with gold. It simply became too expensive.
I rarely do full crowns, for I believe that peeling off the only structurally sound part of the tooth is not necessarily the best idea.
I therefore do much more inlay and inlay type restorations.
I need a reverse undercut for proper insertion of the inlay, but believe in the properties of modern cements as well.
In case of a deep Cl V, I do remove the filling, but lease the overhanging coronal sound tissue. I trust my lab to block this out and accept this to be filled by the cement that I use.
I rarely do a build up in composite, but instead trust the prosthesis material, cement and ferrule to give me a structurally sound prosthesis. And I try to get my margins to be supra gingival if not directly visible.
There are many reasons never to use Impregum ever again. I worked with hydrocolloids, VPS, zinc oxide, alginate and hot hydrocolloids. But the low angle VPS and the trusted alginate -machine mixed are fantastic. Optical impressions, nice, but rarely used in my practice. I like dentistry and am very happy with what my technician makes.
I use cord in the front and for Cl V restorations, but mostly electrosurgery at a very low setting.
Again different to what you do, but it seems to work as well.
And yes, the round bur, cervical margin first, stuck by the shank technique works well, be it that cooling is tricky and overheating is a danger.
It sounds like you’ve got your “systems” and techniques worked out and working well for you. That’s all that matters. If it helps the patient and it works predictably… I like to say, “I can’t argue with success!” 😀