Oral Health Group
Feature

Economical Single Appointment Resin Crowns for Clinical Problem Solving

July 1, 2010
by Mark I. Malterud, DDS, MAGD


Problem solving issues that present in our offices nearly every day is what makes the pursuit of continuing education and learning new techniques imperative to providing consistent quality care to our patients. Whether it is in an article like this, lectures, hands-on classroom training or sitting around with a group of dental friends discussing what we do in our practices, we can pick up tidbits of information that we can take back to our offices to help problem solve the many issues that we encounter daily. Many times in our lives as Dentists, we run into situations that dictate decisions to provide levels of care that differ from what our desires are to deliver for our patients. With the recent downturn in the economy, we are seeing more and more people respond to the suggestion that the best restorative option for a diseased tooth is a crown with a quick reply that they just can’t afford a crown at this time. Many times this is a values issue but more frequently now it is an economic reality.

Other scenarios set up with our senior population that require either placement of a crown due to a large failing restoration or replacement of a crown due to caries created by low salivary flow rates induced by the many drugs our seniors are taking to have a better quality of life. Once this diagnosis for a crown is made, the patient states that either they can’t afford the crown on their fixed income or they don’t believe that they will live long enough to feel comfortable with putting out the funds to pay for the crown. The problem doesn’t stop there, with the numbers of patients we are seeing lately that have nearly 360 degree caries around their teeth due to dietary and lifestyle issues. We are hard pressed to find a way to matrix and restore some of these teeth without creating a full crown and a significant number of these patients are young adults who don’t have the financial wherewithal to have a definitive crown placed to restore these teeth. Even if they did, without first establishing some verifiable lifestyle changes, are we doing them a favor by placing those definitive restorations.

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Another scenario plays out with cancer patients who may question the quality or quantity of life that they have ahead of them and yet they present to your and my offices with distinct dental needs that many times involve the crowning of some of their teeth. These are just some of the scenarios that present that we need to problem solve to help our patients get to a better point in their life or give them the dignity and quality of life to enjoy their final years.

The need for a simple long-term provisional crown is ever-present in our daily treatment of our varied patient base. This article will describe how to effectively use a new product that is based on a variation of a temporization technique that we delegate to our assistants or support staff daily to provide short-term temporaries and this process takes less than an hour to accomplish. Recently, a new product based on a pre-manufactured crown shell came on the market that will allow us as dentists to problem solve many of the issues that were painted as scenarios in the opening paragraph of this article. The technique involves a very inexpensive impression that is poured up with a fast setting hard Vinyl Poly Siloxane die material and then a prefabricated crown sell is fit to the die on this model to create a very inexpensive quick restoration that can be either bonded or cemented to the prepared tooth in a single appointment. These crown shells called DC2 from Direct Crown come in a kits that allows sizes of each of the 16 posterior teeth based on first and second bicuspids and first and second molars in each of the 4 quadrants of the mouth. The DC2 Crown shells are designed for Temporary applications and are made of a heat and pressure cured composite. An updated version called Natural 1 crown shells to be launched pending final FDA marketing approval are created in a neutral enamel shade so that the liner added to the shell will impart the color to the tooth to get a lifelike appearance and will be designed as a long term provisional application. The Natural 1 crown shells are made of a nanohybrid composite to have advanced physical properties and will have 3 sizes of each of the 16 crown shells to allow for nearly all applications we will encounter in our practices. The DC2 has 16 shells which cover all posterior teeth and 8 shells for all of the anterior applications. In my 17 years of fabricating and bonding indirect resin restorations in a single appointment for my patients utilizing various in office lab systems such as Artglass, Belleglass, Solidex, Targis, Cristobal, Sinfony, Gradia Direct, Premise and various direct placement materials used in an indirect technique, I have come to appreciate the ability to fabricate quick accurate working dies to create these restorations. This DC2/ Natural 1 technique actually utilizes this same indirect technique in that the crown shell is lined with direct restorative materials on a firm but flexible vinypoly siloxane die material. This crown system if used intraorally, would, upon polymerization, lock into the interproximal undercuts and any preparation undercuts that may exist and this would lock your restoration onto the prepared tooth. The company and my advice is to never try to fabricate these restorations directly in the mouth as you will lock them on and consequently have to cut them off and refabricate the restoration on a working die.

Once the decision has been made that a crown is the best treatment of choice for the patient and you have established that a long-term provisional crown (Fig. 1) is appropriate for the situation that presents, the tooth is prepared (Fig. 2) and a good quality alginate impression is taken. It needs to be made perfectly clear that for a system like this to work effectively in a dental office, auxillaries need to be utilized. From the time immediately after the impression is placed in the patients mouth, until the polished restoration is brought back to the mouth, an assistant, staff member or in office lab technician can execute the entire process that is being described in this technique. Everything in this process is being done outside the mouth and in essence is a lab fabrication of a long-term provisional restoration. Having the doctor see other patients during this fabrication time is much more effective use of the doctor’s abilities and time.

The final impression of the prepared tooth is done preferably with an alginate over impression of a hydrocolloid wash (Fig. 3) such as Dux Dental’s IDS Syringeable® system to get as much detail as possible. When this simple hydrocolloid/alginate system is used you can take a very fast impression and immediately pour the working die utilizing a very fast setting and accurate vinyl polysiloxane die material such as the Mach 2® or Mach Slo® material from Parkell. In this case Mach Slo is used (Fig. 4) and within three minutes of pulling the alginate/hydrocolloid impression from the mouth you can pour up the impression and have a working die upon which you can fabricate your crown. (On a side note here, there will be a tendency of readers to think that they can use a VPS or Polyether impression of the prepared teeth to achieve a detailed impression and I would caution you that without spraying that impression with a mould or die separator, that in itself will impart a degree of inaccuracy, the VPS die material and bite registration mounting materials will stick to either the VPS or Polyether impression. The Alginate/Hydrocolloid system is ultimately cheaper and gives less problems with the impression and die sticking together.) By using a hinged articulator such as this Die Maker Articulator® from Accubite and available through Patterson Dental, you can establish a fairly decent occlusal pattern by mounting the dies to the articulator using a fast set bite registration material such as Parkell’s BluMousse ®. Once the final articulated (Fig. 5) model is set and ready for use, an appro
priate crown shell is selected (Fig. 6) that fits the buccal lingual size of the prepared tooth. The crown shell is then customized to remove any overextensions that may prevent the shell from being seated or allowing full closure of the articulator. Occlusion is checked (Fig. 7) and if the 20 degree cuspal inclines that the teeth are manufactured with makes the teeth too long for the patients current cuspal situation then some occlusal adjustment is in order to get the articulator fully closed. Once the crown shell can sit passively on the die with the articulator closed, you are ready to line the crown shell. In order to achieve the highest bond with the crown shell to the lining material you will need to air abrade (in this case with a Danville Microetcher®) the surfaces that you want the lining materials to bond to and paint them with the proprietary surface activating resin (Fig. 8). This proprietary material for the DC2 is Parkell’s Add-N-Bond and for the Natural 1, Composive ®. These surface activating materials will increase the bond between the shell and the lining material that you choose.

Air abrading the surface not only creates a microscopically roughened surface texture but it also increases the surface energy to allow a better bond. The Composive® is painted on with a microbrush ensuring that all surfaces to be bonded are covered with a light layer of Composive® resin. Utilizing a strong curing light polymerize the Composive® for 10 seconds. The next step is to add the lining material (Fig. 9) that will fill the void between the passively fitting crown shell and the die of the prepared tooth. As you look at the crown shell you will see that the interproximal areas are cut out to allow the lining composite to take on the shape of the adjacent tooth structure so that the person fabricating the final crown will be able to create an ideal contact for the patients particular situation. The fabricating auxiliary has perfect control of the buccal/lingual size and position along with the occlusal / gingival size and position. The final benefit is that the auxiliary will be able to control the marginal ridge size also with the lining resin. The Composive® lined crown shell is now filled with a fine composite resin such as Ivoclar’s Tetric®, 3M’s Supreme Ultra® or Kuraray’s Majesty Posterior® making sure that you don’t touch the cured Composive lining with anything other than the composite to avoid contaminating the thin oxygen inhibited surface. Being careful to add the lining material into the shell to avoid any air entrapment will create a stronger restoration. The filled crown form is then inverted onto the die and the excess lining resin is removed and any of the margins and contours are refined to approach the final form that is trying to be achieved. Once the final shape of the restoration is settled upon polymerize all surfaces thoroughly. With a very strong curing light such as the Valo® from Ultradent that is used here, polymerize the restoration on the die after the occlusion has been verified. 10 seconds on the mesiobuccal, 10 seconds on the Buccal and then 10 seconds on the Distobuccal and continue around the lingual at those same three points and finish the external cure with 10 seconds on the occlusal. Remove the crown form from the flexible die material and verify that the interproximal material has set.

If you note that there is unpolymerized material interproximally, section the die to expose the interproximal margins place the crown back on the die, reaffirm marginal integrity and then cure the lined crown form on the now single tooth die with the light aimed directly at the interproximals. This doesn’t occur very often but if a darker or more opaque liner is used even a very strong curing light may have difficulty reaching these margins. Once the fully lined crown is removed from the die, give the internal aspect of the crown a 10 second final cure to be sure that any potentially unpolymerized material is set. The fabricator of the crown is now ready to final shape and polish the restoration (Fig. 10, 11). Any good silicone diamond polishing wheel on a low speed straight handpiece will make rapid work of the contouring of the external surface of the tooth to achieve the final contours and refine the margins. Moving to a finer polishing grit will impart a luster that can then be taken to a high shine with a gentle buffing with a cotton disk or goat hair polishing brush. The DC2/Natural 1 crown is now ready to take back to the patient to verify the fit, contacts and contours. If all of the parameters are achieved the restoration is bonded to the prepared tooth or one of the self etching resin cements is used to affix the crown to the prepared tooth. This particular crown was placed using 3M’s Unicem®. The final cemented/bonded crown is checked for final occlusion and any adjustment areas are polished interorally with a finishing polish point such as the Vivadent Astropol® that was used here. The final restoration is completed in less than an hour, generally in about 45 minutes, and the patient has an extremely accurate resin crown (Figs. 12, 13) that will allow them to get to that other point in their life that they discussed with you when their original diagnosis dictated coronal coverage. By having this problem solving Direct Crown DC2 and eventually Natural 1 NanoHybrid crown shell kit in the office, dentists are able to help a wide variety of patients who may not be able to afford the more definitive treatments that have been offered to them and the office can feel good about providing a very viable and longer term solution for the particular problem presented. The economics of providing these types of indirect resin crowns creates and opportunity to help a wide segment of our population that is struggling with managing their money and still be profitable to keep a dental practice healthy. The breakdown of expenses for all the materials necessary to provide this type of service is around $35 US per unit and doesn’t require the lease or loan payment for an expensive milling machine or their blocks of milling blanks. This truly is an inexpensive problem solving solution to many of the situations that we see daily in our busy dental practices. OH

Dr Malterud practices general and family dentistry in St. Paul, MN, along with being a faculty member of the University of Minnesota Continuing Dental Education Department. Dr. Malterud’s practice focuses on comprehensive cosmetic dentistry incorporating Minimally Invasive Dental Procedures. Dr. Malterud is an active member of the American Dental Association, and its state and local components, Academy of General Dentistry (where he is currently the Minnesota Immediate Past President and Chairs The AGDs Dental Education Council and some task forces). Dr. Malterud also consults with various other dental manufacturers on product development and testing.

Oral Health welcomes this original article.