Crown prep and build-up tip!

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 facial abfraction and large amalgam with cracks evident.  Tx Plan:  Build-up and crown.

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:

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20 Responses to Crown prep and build-up tip!

  1. Victor Martel says:

    Great minds think alike!

  2. 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!

  3. Brad Blair says:

    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.

  4. Madmike says:

    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

  5. Alex says:

    Very nice pictures !
    What camera do you use ?

    • The Dental Warrior says:

      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.

  6. John L says:

    Me Likey!! Great tip Mike!

  7. The Dental Warrior says:

    I can’t believe this post is currently the 3rd most popular!

  8. Beth says:

    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.

    • The Dental Warrior says:

      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).

  9. falk burger says:

    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.

  10. Dr.Farzin says:

    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

  11. Michel Raad says:

    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.

  12. reshma says:

    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

    • The Dental Warrior says:

      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!

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