In many cases, cracks in teeth resulting from root canal treatment can require full coverage with a crown in order to restore them to their original strength. With an ever-increasing number of patients with older fillings coming into our offices, this procedure has become very common. Prior to preparing the teeth for crowns, the root canal access must be sealed and “built up.”
This article presents the technique and materials I have used to build up a tooth that has had prior endodontic treatment and prepare it for a full crown.
CASE REPORTS
Case No. 1
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| Figure 1. Original condition of tooth. | Figure 2. Removal of temporary and decay. Note multiple cracks in pulpal floor. |
The patient came to see me to restore a tooth that had previously had root canal therapy. After removing the temporary filling, several cracks were evident in the tooth (Figures 1 and 2). While the root canal access was conservative, because of the cracks and the patient”™s occlusion, I prescribed a buildup followed by full coverage with a crown. I started the buildup preparation by removing a small amount of decay I found under the temporary. I tried to preserve as much of the existing tooth structure as possible.
Materials and Technique
Although there are numerous core materials available, I choose LuxaCore Dual (Zenith/DMG) because it is a very efficient and durable composite material that is particularly useful for this type of procedure. Its palm-held Smartmix delivery system takes little effort on the part of the assistant or dentist to build up a tooth prior to preparing it for a crown, and the automix syringe delivers a consistent mix every time.
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| Figure 3. Application of Contax. |
Before LuxaCore can be injected into the preparation, the tooth must be conditioned for bonding. It is etched and primed using Contax Bonding Agent (Zenith/DMG). Contax is aself-etching, self-conditioning bonding system that can be used in a wet, moist, or dry oral environment. My assistant places a single drop of Bottle A (Contax Primer) into a dappen dish. I then apply the first layer for 20 seconds. It is important to continue rubbing the layer for a full 20 seconds. This layer is etching the tooth along with placing a layer of primer. The second layer from Bottle B (Contax Bond) is then applied in the same manner. While you do need to rub the material with a microbrush for longer then nonetching primer systems, the total application time is the same for both methods. (Figure 3). Contax is thicker than conventional primer and adhesive systems, so care must be taken not to let it “pool” in the preparation, but if you follow the recommendation of a full 20 seconds of application of each layer, this is not a problem. After rubbing the second layer for a full 20 seconds, I cure it for 20 seconds with my PAC light (American Dental Technologies). The tooth should have a “wet” appearance at this time. Now I am ready to inject the LuxaCore Dual.
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| Figure 4. Smartmix syringe tip inside prep. |
LuxaCore Dual comes in 3 different shades-natural, white, and blue. A composite buildup material must be very strong but also easy to apply to the tooth. This system makes building up a tooth very simple and efficient. As soon as the prep is primed, my assistant simply hands me the Smartmix syringe and I inject it into the tooth; I do not have to wait for her to mix anything or load it (Figure 4). LuxaCore Dual is not very viscous and flows very easily into the prep, ensuring complete adaptation to the preparation walls. It does not slump. When injecting it into the tooth, I place the plunger of the syringe into the palm of my hand. I do not use my thumb to depress it. This gives me greater control. I do not let the intraoral tip of the syringe become imbedded in the material as it flows out. If this happens, a void could be created. I start at the bottom of the prep and lift the syringe out of the tooth as I back fill. If I am worried about slumping, I will simply stop and cure the material for 5 seconds, then continue injecting with the same syringe. After the prep is filled, I cure it for 20 seconds with my PAC light. I am not concerned about fully curing the material since it is dual- cured and will set by itself.
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| Figure 5. Final prep. |
I can now begin preparing the tooth for a crown. I do this with the rubber dam (Ultradent) still in place. This provides both my assistant and me with a clear view and access to the preparation and keeps the patient from swallowing any of the tooth and dust. Preparing as much of the tooth as I can with the rubber dam still in place has greatly increased my efficiency. I prepare the occlusal using depth guides, followed by a wheel diamond. The wheel is easier to use for preparing both the buccal and lingual occlusal surfaces. I then prepare the sides of the tooth as far as the rubber dam will allow. If multiple teeth are isolated, I will split the dam so I have access to the entire tooth. After I prepare all that I can, I then remove the rubber dam and finalize my preparation. Notice in Figure 5 that 95% of the preparation is completed at this point. It is a simple step to refine my gingival margins and check to make sure I have enough occlusal reduction. By using the rubber dam for the preparation, I have saved both the patient and me considerable time and made it easier for the patient during the procedure.
Case No. 2
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| Figure 6. Original condition of tooth. |
The patient presented with a crown that came off over the weekend. The tooth had originally been built up with amalgam. There was extensive decay, and I assumed that the crown had been leaking for some time. The tooth was decayed well below the gum line, which would make access difficult and isolation virtually impossible (Figure 6). I always restore teeth with a rubber dam when possible, but not in this case. Because of the shape of her mandible, I could not even position the rubber dam clamp over the tooth. I did talk to the patient about the difficulty of the case and the benefits of an implant or at the very least crown-lengthening. She preferred to try to restore the tooth with a crown, and if that failed, she would consider an implant.
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| Figure 7. Removal of decay. |
After I removed the amalgam and cleaned up the tooth, it was clear that bonding to this tooth was going to be a challenge. The preparation was well below the gum line, and access was inadequate because of the tooth”™s position and the limited opening of the patient (Figure 7). This is a case where Contax is particularly useful. Because we could not use a rubber dam, traditional bonding methods would be unpredictable at best. Even washing off the etchant and keeping the patient from closing and contaminating the etched tooth would have been a major challenge. With the use of a self-etching primer, this step could be avoided.
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| Figure 8. Application of Contax. |
I removed all the decay with a round bur until I found solid tooth structure. I did not like leaving some of the staining, but the tooth structure was solid, and I was pretty far into the tooth. The last thing I wanted was to perforate the floor of the preparation. Contax Primer was applied for 20 seconds with constant rubbing (Figure 8) followed by Contax Bond, then light-curing for 20 seconds.
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| Figure 9. Buildup with Luxacore Blue. Note easily visible neon color. |
I chose to use the blue-colored LuxaCore Dual for this case. The color is light blue when it comes out of the syringe but turns almost neon blue after it is cured. The color makes it very easy to see even in the most difficult situations. I did not use a matrix band to isolate the preparation because I was afraid it would induce bleeding. So, I just filled the prep with blue LuxaCore (Figure 9). The floor of the pulp chamber was 4 to 6 mm into the tooth, so I was not worried about retention of the core.
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| Figure 10. Evaluation of final prep. Note how easy it is to see some Luxacore on distal margin. |
I then removed some gingival tissue from the distal of the tooth in order to expose my margin. I knew I was going to have trouble seeing the margin, even with magnification. I then completed my crown preparation. Note in Figure 10 how the blue LuxaCore is easily seen on the distal margin, even with the bleeding tissue. This was then easily removed and impressions were taken.
CONCLUSION
Two cases have been presented that required a core buildup and full crown in teeth that had previous endodontic treatment. The materials and technique for placing the core buildup and preparing the teeth for full coverage restorations were discussed.
Dr. Soileau is a general dentist from Lafayette, La. His practice focuses on restorative rehabilitation and cosmetic enhancements. He lectures nationally and internationally on the use of digital photography and computer assistance for diagnosing, treatment planning, and performing comprehensive dental procedures. He is a consultant for several technology-based dental manufacturers and beta tests many of their products. When Dr. Soileau is not lecturing, he is a consultant to several pageant coaches throughout the country. He has judged and worked with local and national Miss USA, Miss Teen USA, Miss America, and Mrs. America contestants. He is co-director of Digital Photography for GenR8TNext Digital Photography Courses and has taught digital photography at the Institute of Oral Art and Design in Tampa and the Pacific Aesthetic Continuum (PAC~Live) in San Francisco. His dental and photography skills can be seen on his Web site at smilesbysoileau.com, and he can be contacted at (337) 234-3551 or tony@smilesbysoileau.com.
