Letters to the Editor

February 9, 2010

Dear Dr. DiTolla,

I am a fourth year dental student at the University of Florida and I love watching your clinical videos from Glidewell. I am interested in trying out your Reverse Preparation Technique bur block. Roughly how many uses can you get out of each bur on typical crown and bridge cases before it starts getting dull and needs to be replaced?

– Anis Elkhechen, Dental Student
University of Florida

Dear Anis,

Nice to hear from you! Well, the workhorse bur is the 856-025 and I probably get three or four preps out of it. If I do the occlusal reduction with the football bur instead of the 856-025, I can get more uses out of the 856-025. I order the 856-025 in batches of 100 and just rotate it into the Reverse Preparation Kit as needed. I use the depth cutters slowly with light pressure to keep them from clogging and dulling quickly. I hope that helps!

– Dr. DiTolla

Dear Dr. DiTolla,

I’m not sure if I’ve come to the right place to contact you on an educational level. I’m graduating this year and have recently been watching your clinical videos, which I love! They are outstanding and very educational. I wanted to ask you a couple of questions. If you find the time to answer them, I would appreciate it.

1) For porcelain (nonmetal) restorations I’ve been taught a shoulder margin is required. Should I use a flat end bur for the 90-degree shoulder or is it appropriate to use a rounded torpedo bur?

2) You use a round bur in one of your videos to prepare the finish line for a veneer. Is it OK if I stick with a round-ended taper bur?

3) We work with light body and heavy body silicone two-stage impression for preps. After the putty impression, my teachers make grooves and channels in the impression. Is this necessary and what is the point, really? Why do you take both phases at once?

4) With regards to the retraction cord, will we leave the retraction cord for the first stage and remove it for the light body stage? I’m not really sure when to leave the retraction cord in or take it out. I always assumed to leave it in for however long was required, then take it out and take the impression whether it’s one stage or two. What are your views? Thank you very much, and if you manage to answer any I am grateful.

– Alidad Daftari, Dental Student
London, United Kingdom

Dear Alidad,

Thanks for your kind words! To answer your questions…

1) For porcelain restorations, it is preferable to have a rounded internal line angle rather than a 90-degree shoulder. The KR burs will achieve this, and my favorite, the 856-025, will do it as well. Both of these burs are not quite as pointed as a torpedo bur.

2) Yes, of course you can use a round end taper bur for your margin formation. I just find it really fast and easy to use the 801-021 bur and then use the round end taper (856-025) to blend the margin with the rest of the axial reduction.

3) The relief that your teachers are having you put in the putty material is to ensure the entire preparation is surrounded with light body material from the tray being able to seat completely. I don’t use putty at all, actually; I use medium body as my syringe material and heavy body in the tray. Using putty is simply a cost-saving method that leads to more problems than it is worth. Taking a simultaneous impression where both materials set together prevents several different problems from occurring and is the preferred method for taking quality impressions, although they may be slightly more expensive.

4) I refuse to take two-stage impressions. It makes no sense to me. I pack two different retraction cords: a size 00 cord goes in the sulcus first while I am preparing the tooth, and the second cord (size 2 typically) goes in when I am done with the preparation. The size 2 cord stays in for eight to 10 minutes and then is removed, leaving the 00 cord in the sulcus while I syringe the medium body material around the tooth. At the same time my assistant expresses heavy body material into the tray and then I seat that in the patient’s mouth. The 00 cord is removed either after the impression or after the temps are cemented.

– Dr. DiTolla

Dear Dr. DiTolla,

I am concerned with not sealing exposed dentin, even for a short period of time. With dentinal tubules numbering in the tens of thousands per square millimeter and bacteria numbering in the billions in the oral cavity, not sealing this with some sort of temporary luting agent for any period of time seems unwise. Dr. Charlie Cox and others have shown the seal is the deal to prevent pulpitis, whether temps break or not. Do you agree? I am obviously an endodontist. I do a lot of RCTs on previous virgin teeth from “veneers,” 15 out of 20 on one patient — all teeth virgin to start with and then necrotic with radiolucencies within three to six months, with the dentist making her (a 24-year-old) a long-term dental cripple. I see you do try to emphasize that you are not prepping into dentin as much, but most dentists need to have the idea of protecting the pulp jammed into their brains. Remember, whatever you tell them will get applied to almost any restorative situation!

– Anonymous

Dear Anonymous,

I am concerned with not sealing exposed dentin as well; it has always been a shortcoming to the prepped veneer/shrink-wrap temp technique. As time went on, I began to apply a bonding agent to the dentin prior to temporization, even though I knew it could theoretically affect fit. I personally have a case where I prepped 10 virgin teeth for veneers into the dentin as I was taught, and three of them ended up needing endodontic therapy. After that case, I drew a mental “line in the sand” and decided not to expose dentin unless I could care for it properly. Fortunately, at the same time we introduced Prismatik ThinPress™ ceramic material, which made 0.3 mm veneers a reality and made it unnecessary to remove all of the facial enamel.

Are we really being conservative if we are able to prepare teeth less, but protect them less during provisionalization and subject them to possible pupal death? Conservatism needs to apply to the pupal tissues as well as the enamel, and today I believe that by removing only enamel for my veneers (and many times no enamel on half the teeth), I may make a small sacrifice in the pursuit of ultimate esthetics to protect the long-term health of the teeth. I doubt many patients would say they want lobe development and incisal translucency in their veneers, even if it meant that some of their teeth might need endo.

– Dr. DiTolla