april 2014 9
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TK1 – A viable alternative to conventional dentures A prosthesis supported by telescopic crowns. By Dr Bernard Martin Mayston & DTM Ulrich Heker
■ To provide an understanding of the reasons for and methods of creating a telescopic retained prosthesis using a device to adjust the friction between the telescopic components
A case report: the use of telescopic crowns to restore an upper arch of teeth
P
atients in many European countries are increasingly conscious of the aesthetic potential, practicality and cost effectiveness of precision connecting elements, such as telescopic crowns and attachments.
The techniques presented are not new: I used to provide telescopic crowns in my practice over 20 years ago but I stopped using them because of the constraints of the NHS contract – at the time, the costs seemed relatively high. I also struggled to find a local British dental technician who could produce the high quality, precision fit necessary to achieve the desired result. Today, things are different in several ways. More dental treatments are provided privately and if the necessary skills are not available within the UK, I can access those techniques from further afield – in this case, Germany. The article on Skype that featured in the last issue of TT
These methods are within the reach of many UK dental practitioners with recourse to dental technicians, and this article gives an illustrated overview of the basic principles of these techniques. Fig. 1: Showing the suboptimal arrangement of existing gaps.
illustrates perfectly how technology makes our world a lot smaller and more accessible. In Germany they seem to provide this treatment more frequently, and so have perfected the telescope crown-retained prosthesis technique more than we have in the UK. In fact, it is often called the German crown technique.
The case A 69-year-old man presented with a failing upper arch of teeth. He had extensive crown and bridge work, provided about 20 years before, to replace a conventional denture that he had been unhappy with. Over the last few years he had lost several posterior teeth. This lack of posterior support meant that there was an increasing amount of pressure on his large upper anterior bridge. The large upper anterior bridge had recently worked loose a couple of times and required root canal treatment and a post at his upper left canine tooth (tooth 23), which had weakened the abutment at the left side of the anterior upper bridge. The posterior bridge on his upper left side had recently been sectioned when the mesial abutment (tooth 24) had failed and had to be removed, leaving the pontic cantilevered off the molar (tooth 26). This upper left molar (tooth 26) had infection in the trifurcation area (between the roots) and so was failing.
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■ CPD aims and objectives are to: – understand the main features of a telescopic retained prosthesis – identify the various components of the actual patient’s case as described – recognise why and how a friction device such as TK-1 might be used – gain an understanding as to how a telescopic retained prosthesis might be constructed
This article features a case solved with TK1 telescopes in cooperation with Ulrich Heker, a German dental technician whose work has been featured in The Technologist previously.
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Educational aims, objectives and outcomes
Fig. 2: The upper bridges still look reasonably good after 20 years, but the abutment teeth are failing underneath.
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Importantly, if there is ever a problem with an abutment tooth underneath, the telescope-retained prosthesis is easily removed to treat the problem tooth and then replaced. If one abutment tooth fails, then it will not usually cause the failure of the whole prosthesis. We felt that this was a major benefit of this treatment. Fig. 3a: X-rays of the failing bridge.
Fig. 3b: The lower jaw, another field.
Discussing all the options: Dentures, bridges or implants Dentures are usually the quickest, easiest and cheapest way to replace missing natural teeth. All that’s needed is an impression of the mouth and a few measurements, such as the way the teeth bite together. The dental technician then makes the dentures and they are usually ready to be fitted within a few weeks. The patient did not want to have his palate covered with a denture. He had experience of wearing a denture before. Previous dentures had been loose and he found that he did not enjoy eating his food as much when he was wearing a denture. On a partial denture, sometimes clasps can spoil the cosmetic appearance of the prosthesis and, with heavily restored natural teeth, it can be difficult to get a good colour match with the denture teeth. Implants seem to be a good option but add considerable financial cost to the treatment and not all patients can afford the extra expense. Implants also involve more complex and invasive treatment and a much longer treatment time (usually at least 4 to 6 months), which is not always
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Pretreatment acceptable to the patient. Sometimes there is insufficient bone and frequently there is poor bone quality in the upper molar areas which leads to compromises in the final prosthesis. This usually leads to a shortened dental arch with only ten anterior teeth. Some specialists feel that this lack of posterior support can upset the temporomandibular joint. Lastly, the cosmetic results can sometimes be disappointing with an implant-retained prosthesis, as the prosthetic teeth often have to be made very long or misshaped to fit into the bone and the space where the implants can be placed. This is more of a problem in patients with a high lip line. A conventional bridge would have been possible, but was considered inappropriate because there were insufficient abutment teeth to support a bridge, no distal abutment tooth on the upper right side and, with a history of failing abutment teeth, this option was doomed to fail. If one abutment tooth became a problem – as we suspected it would – then it might cause the failure of the whole bridge. A telescope-retained full upper prosthesis was considered the best option, as this restored the full upper arch of teeth, without covering the palate (as a denture would) and would be a much better fit than a denture. This option would cost less than implants, involve less invasive treatment and deliver a quicker result than implants. It would also have the feel of a bridge that the patient was used to and happy with.
In one long appointment we removed the old failing bridges and treated any infection and disease in the abutment teeth. This included root canal treatment in the upper right canine tooth and removing the mesial root on the upper left first permanent molar tooth in order to clean out the infection in the trifurcation area, whilst keeping the distal and palatal roots for an abutment. After some briefings with the lab in Germany we estimated a treatment time of 5 weeks from the preparation day, including try-ins and finishing.
A cost-effective alternative to gold telescopic crowns The classic way involves constructing primary & secondary crowns made of gold alloy. The secondary crowns are soldered to the chrome-cobalt frame of the prosthesis. The friction necessary to hold the prosthesis in position is based on the mechanical properties of the gold alloy. The gold alloy adds considerable cost to the prosthesis. Therefore, the TK1 method has been developed, where primary and secondary crowns are made in a cheaper chrome-cobalt alloy. This saves the cost of the gold alloy and, as the secondary crowns can be incorporated into the casting of the chrome-cobalt frame of the prosthesis, also saves the stage where the secondary crowns are soldered to the prosthesis. Here the friction is adjustable and controlled by the TK1 elements that are positioned beside the primary inner crown elements.
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We made the temporary bridge thicker and stronger than usual, as it had to last a little longer and be removed and recemented at the ‘try-in’ stages.
e) Every TK1 element can be easily exchanged by reversing this procedure, while the patient is sitting in the chair.
We then had a series of appointments to try-in the inner telescope crowns and take a locating impression with the inner telescope crowns in position. Then trying in the whole prosthesis at the wax up stage before the final fitting appointment.
Fig. 9: The one-cast metal frame for the prosthesis.
Fig. 10: The metal frame set on the primary crowns on the model.
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Fig. 5: The abutment teeth were prepared and a Impregum impression was taken and a temporary bridge made.
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Fig. 4: The starting point. The situation after removing the old bridges showing the lack of tooth structure, confirming why we felt that conventional bridges would be unsuccessful in the long term.
The lab work How the TK1 element works a) Before duplication, in order to get the investment material model, the tiny black placeholder has to be positioned seamlessly and parallel to the primary crowns. It must be removed from the silicone mould before casting. b) On the investment model, the moulded placeholder is completely covered by the wax up. c) After finishing the prosthesis, the TK1 elements are inserted in this space (see Fig. 11). d) The first few turns of the tiny screw secure its hold in the TK1; further turns then expand the retention to adjust the friction.
Fig. 7: After the first try-in, including a pickup impression for the following master model – the milled and polished primary crowns. We can clearly see the milling angle of 2°. Fig. 11: The finished prosthesis.
Fig. 8: Like Fig. 7, seen from above. Fig. 12: Placing the finished prosthesis on the model.
Fig. 6: How the TK1 element works.
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12 april 2014
denturealternatives How to:
Fig. 13: The finished work on its model.
The upper right lateral incisor was tipped at an angle which made it impossible to get it parallel with the other telescope crowns. Therefore, it was restored with a bonded porcelain crown and the palatal side was made parallel with the other telescopes.
When cementing the primary inner crowns, if any one crown does not sit correctly, it will spoil the fit of the prosthesis. It is therefore worth placing the primary inner crowns in the prosthesis so they are held in the correct orientation and, if possible, cementing them all at the same time, to be assured that they all sit correctly and do not spoil the fit.
After cementing the primary crowns, we initially fit the prosthesis loosely, so the patient can get used to fitting and removing it themselves. A few days later at a follow-up appointment, we adjust the screws in the TK1 attachment to get the required tightness of fit.
In this case, we cemented the bonded crown on tooth 12 separately because the angulation of this tooth and the path of insertion made it impossible to cement it at the same time as the other crowns. The prosthesis should be carefully smeared with Vaseline速 so that any excess cement will not cement the prosthesis in, will not foul the attachment screws and can easily be removed from the prosthesis.
Fig. 18: The prosthesis in position.
Fig. 14: Inner telescope crowns in position: Telescopes on 23, 26, 13, 14 and the bonded porcelain crown on 12. Fig. 19: No clasps necessary and with a full arch prosthesis, no problems with colour matching.
Fig. 16: Prosthesis seen from below. Notice the two TK1 elements in position.
Fig. 15: Finally, placing the prosthesis, locating it on the primary inner crowns.
Fig. 17: The tiny screws are easy to adjust with a small screwdriver and give strength to the friction fit of the prosthesis.
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Discussion In this case we went straight from the failing fixed bridges to the telescope crown-retained prosthesis. This put a lot of pressure on the dentist to fix whatever we found underneath the bridges and make a good temporary bridge at one long appointment. I now think that in some cases it might be worth removing the old bridges and having a temporary denture made and fitted. This would allow a better assessment of the abutment teeth before we commit to a treatment plan (some teeth might be worse than expected and be unrepairable and spoil the treatment plan). More appointments can then be allocated
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Fig. 21: A satisfied patient.
The TK1 arguments in a nutshell ■ Invisible prosthesis by the elimination of unaesthetic clasps ■ Very easy to insert (> 2° milling) ■ A sleeker design by using non-precious alloy ■ Better force distribution to supporting teeth ■ Durable (no solder, no other joints) ■ Very short adaptation phase ■ The friction of every single telescope can be adjusted simply ■ Improved comfort and chewing efficiency ■ Very easy, fast and inexpensive to extend ■ A very good price/performance ratio (no precious alloy and solder)
Increasingly we are seeing older patients who have lived through the ‘drill and fill’ years of dentistry, who have heavily restored mouths and consequently a lack of good tooth structure to work with. As their teeth start to fail, the decision on how to restore their mouths can be increasingly difficult. I find that a lot of these patients do not want to wear a denture and either cannot afford the cost of implants or do not like the idea of the invasive treatment involved with implant treatment. All general dental practitioners will have the skills necessary to provide this treatment, so this may save having to refer to an implant specialist. Obviously case selection is very important, but I feel that a telescope crown-retained prosthesis can be a useful alternative option to offer some of these patients. In the UK this is an option that we often forget to offer. As the cost of dental treatment increases, patients want to know how long restorations will last, so they can assess if they are going to get good value for their money. As clinicians we know that it is almost impossible to guarantee any dental work and heavily restored teeth tend to be the most unreliable. For me, the fact that the telescope crown-retained prosthesis is easily removed means that I am confident that I can sort out a problem with an abutment tooth underneath. Also, if there are several abutment teeth available to accept the telescope crowns, then if one tooth fails and we have to extract it, then usually we do not lose the whole prosthesis. The prosthesis will usually hold pretty well with one less abutment tooth. So whilst I cannot guarantee that the patient will not have a problem, I am much more confident that I will be able to fix it if it happens.
Dr Bernard Martin Mayston BDS London is the principal/owner of Diss Dental Care Centre. Member of www.norwichdentistsstudygroup.co.uk Dr Mayston has been caring for his patients in Diss and its surrounding area for over 28 years. Dr Bernard Martin Mayston Diss Dental Care Centre, Oxford House 127 Victoria Rd, Diss, Norfolk IP22 4JN UK Phone: +44 1379 643 789 Email: dissdentalcarecentre@hotmail.co.uk
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Fig. 20: A successful treatment.
Conclusion
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to treat the abutment teeth at a convenient time. Also, if a patient has had to tolerate a temporary acrylic denture for a while then they appreciate the benefits of the superior telescope crown-retained prosthesis much more.
Ulrich Heker is the owner-manager of Ulrich Heker Dental Laboratory founded in 1996 with the strap line TEETH ‘R’ US. As a qualified master craftsman (German Master Dental Technician) since 1991, he has over 26 years’ experience both at the bench and in running a successful business. Ulrich lives in Mülheim on the river Ruhr and is an accomplished ‘western-style’ rider in his spare time. Ulrich is fluent in English and can be contacted at: Corneliastr. 17, D-45130 Essen, Germany Phone: +49 201 797 955 Video skype: teeth.are.us Web: http://www.teethrus.de Email: ulrich@teethrus.de
I also think that the telescope crownretained prosthesis can be a better transition towards a full denture.
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