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TK1 – A viable alternativeto conventional dentures

Educational aims, objectives and outcomes

■ 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

■ 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

A prosthesis supported by telescopic crowns. By Dr Bernard Martin Mayston & DTM Ulrich Heker

This article features a case solved withTK1 telescopes in cooperation with Ulrich Heker, a German dental technicianwhose work has been featured in TheTechnologist previously.

The techniques presented are not new: Iused to provide telescopic crowns in mypractice over 20 years ago but I stoppedusing them because of the constraints ofthe NHS contract – at the time, the costsseemed relatively high. I also struggled tofind a local British dental technician whocould produce the high quality, precisionfit necessary to achieve the desired result.

Today, things are different in several ways.More dental treatments are providedprivately and if the necessary skills are notavailable within the UK, I can accessthose techniques from further afield – inthis case, Germany. The article on Skypethat featured in the last issue of TT

illustrates perfectly how technology makesour world a lot smaller and moreaccessible. In Germany they seem toprovide this treatment more frequently,and so have perfected the telescopecrown-retained prosthesis technique morethan we have in the UK. In fact, it is oftencalled the German crown technique.

The caseA 69-year-old man presented with afailing upper arch of teeth. He hadextensive crown and bridge work,provided about 20 years before, toreplace a conventional denture that hehad been unhappy with. Over the last fewyears he had lost several posterior teeth.This lack of posterior support meant thatthere was an increasing amount ofpressure on his large upper anteriorbridge. The large upper anterior bridgehad recently worked loose a couple oftimes and required root canal treatmentand a post at his upper left canine tooth(tooth 23), which had weakened theabutment at the left side of the anteriorupper bridge. The posterior bridge on hisupper left side had recently beensectioned when the mesial abutment(tooth 24) had failed and had to beremoved, leaving the pontic cantileveredoff the molar (tooth 26). This upper leftmolar (tooth 26) had infection in thetrifurcation area (between the roots) andso was failing.

A case report: the use oftelescopic crowns to restore anupper arch of teeth

Patients in many Europeancountries are increasinglyconscious of the aesthetic

potential, practicality and costeffectiveness of precision connectingelements, such as telescopic crowns andattachments.

These methods are within the reach ofmany UK dental practitioners withrecourse to dental technicians, and thisarticle gives an illustrated overview of thebasic principles of these techniques.

Fig. 1: Showing the suboptimal arrangementof existing gaps.

Fig. 2: The upper bridges still look reasonably good after 20 years, but the abutment teeth are failing underneath.

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acceptable to the patient. Sometimesthere is insufficient bone and frequentlythere is poor bone quality in the uppermolar areas which leads to compromisesin the final prosthesis. This usually leadsto a shortened dental arch with only tenanterior teeth. Some specialists feel thatthis lack of posterior support can upsetthe temporomandibular joint. Lastly, thecosmetic results can sometimes bedisappointing with an implant-retainedprosthesis, as the prosthetic teeth oftenhave to be made very long or misshapedto fit into the bone and the space wherethe implants can be placed. This is moreof a problem in patients with a high lipline.

A conventional bridge would have beenpossible, but was consideredinappropriate because there wereinsufficient abutment teeth to support abridge, no distal abutment tooth on theupper right side and, with a history offailing abutment teeth, this option wasdoomed to fail. If one abutment toothbecame a problem – as we suspected itwould – then it might cause the failure ofthe whole bridge.

A telescope-retained full upper prosthesiswas considered the best option, as thisrestored the full upper arch of teeth,without covering the palate (as a denturewould) and would be a much better fitthan a denture. This option would costless than implants, involve less invasivetreatment and deliver a quicker resultthan implants. It would also have the feelof a bridge that the patient was used toand happy with.

Importantly, if there is ever a problemwith an abutment tooth underneath, thetelescope-retained prosthesis is easilyremoved to treat the problem tooth andthen replaced. If one abutment tooth fails,then it will not usually cause the failure ofthe whole prosthesis. We felt that this wasa major benefit of this treatment.

PretreatmentIn one long appointment we removed theold failing bridges and treated anyinfection and disease in the abutmentteeth. This included root canal treatmentin the upper right canine tooth andremoving the mesial root on the upperleft first permanent molar tooth in orderto clean out the infection in thetrifurcation area, whilst keeping the distaland palatal roots for an abutment.After some briefings with the lab inGermany we estimated a treatment timeof 5 weeks from the preparation day,including try-ins and finishing.

A cost-effective alternative to gold telescopic crownsThe classic way involves constructingprimary & secondary crowns made of goldalloy. The secondary crowns are solderedto the chrome-cobalt frame of theprosthesis. The friction necessary to holdthe prosthesis in position is based on themechanical properties of the gold alloy.

The gold alloy adds considerable cost tothe prosthesis. Therefore, the TK1method has been developed, whereprimary and secondary crowns are madein a cheaper chrome-cobalt alloy. Thissaves the cost of the gold alloy and, asthe secondary crowns can beincorporated into the casting of thechrome-cobalt frame of the prosthesis,also saves the stage where the secondarycrowns are soldered to the prosthesis.

Here the friction is adjustable andcontrolled by the TK1 elements that arepositioned beside the primary innercrown elements.

Discussing all the options:Dentures, bridges or implantsDentures are usually the quickest, easiestand cheapest way to replace missingnatural teeth. All that’s needed is animpression of the mouth and a fewmeasurements, such as the way the teethbite together. The dental technician thenmakes the dentures and they are usuallyready to be fitted within a few weeks. Thepatient did not want to have his palatecovered with a denture. He hadexperience of wearing a denture before.Previous dentures had been loose and hefound that he did not enjoy eating hisfood as much when he was wearing adenture. On a partial denture, sometimesclasps can spoil the cosmetic appearanceof the prosthesis and, with heavily restorednatural teeth, it can be difficult to get agood colour match with the denture teeth.

Implants seem to be a good option butadd considerable financial cost to thetreatment and not all patients can affordthe extra expense. Implants also involvemore complex and invasive treatment anda much longer treatment time (usually atleast 4 to 6 months), which is not always

Fig. 3a: X-rays of the failing bridge.

Fig. 3b: The lower jaw, another field.

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We made the temporary bridge thickerand stronger than usual, as it had to last alittle longer and be removed and re-cemented at the ‘try-in’ stages.

We then had a series of appointments totry-in the inner telescope crowns and takea locating impression with the innertelescope crowns in position. Then tryingin the whole prosthesis at the wax upstage before the final fitting appointment.

The lab workHow the TK1 element worksa) Before duplication, in order to get the

investment material model, the tinyblack placeholder has to be positionedseamlessly and parallel to the primarycrowns. It must be removed from thesilicone mould before casting.

b) On the investment model, themoulded placeholder is completelycovered by the wax up.

c) After finishing the prosthesis, the TK1elements are inserted in this space(see Fig. 11).

d) The first few turns of the tiny screwsecure its hold in the TK1; furtherturns then expand the retention toadjust the friction.

e) Every TK1 element can be easilyexchanged by reversing this procedure,while the patient is sitting in the chair.

Fig. 4: The starting point. The situation afterremoving the old bridges showing the lack oftooth structure, confirming why we felt thatconventional bridges would be unsuccessfulin the long term.

Fig. 5: The abutment teeth were preparedand a Impregum impression was taken and atemporary bridge made.

Fig. 7: After the first try-in, including a pickupimpression for the following master model –the milled and polished primary crowns. Wecan clearly see the milling angle of 2°.

Fig. 8: Like Fig. 7, seen from above.

Fig. 6: How the TK1 element works.

Fig. 9: The one-cast metal frame for theprosthesis.

Fig. 10: The metal frame set on the primarycrowns on the model.

Fig. 11: The finished prosthesis.

Fig. 12: Placing the finished prosthesis on the model.

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After cementing the primary crowns, weinitially fit the prosthesis loosely, so thepatient can get used to fitting andremoving it themselves. A few days laterat a follow-up appointment, we adjust thescrews in the TK1 attachment to get therequired tightness of fit.

DiscussionIn this case we went straight from thefailing fixed bridges to the telescopecrown-retained prosthesis. This put a lotof pressure on the dentist to fix whateverwe found underneath the bridges andmake a good temporary bridge at onelong appointment. I now think that insome cases it might be worth removingthe old bridges and having a temporarydenture made and fitted.

This would allow a better assessment ofthe abutment teeth before we commit toa treatment plan (some teeth might beworse than expected and be un-repairable and spoil the treatment plan).More appointments can then be allocated

How to: When cementing the primary innercrowns, if any one crown does not sitcorrectly, it will spoil the fit of theprosthesis. It is therefore worth placingthe primary inner crowns in the prosthesisso they are held in the correct orientationand, if possible, cementing them all at thesame time, to be assured that they all sitcorrectly and do not spoil the fit.

In this case, we cemented the bondedcrown on tooth 12 separately becausethe angulation of this tooth and the pathof insertion made it impossible to cementit at the same time as the other crowns.

The prosthesis should be carefullysmeared with Vaseline® so that anyexcess cement will not cement theprosthesis in, will not foul the attachmentscrews and can easily be removed fromthe prosthesis.

Fig. 13: The finished work on its model.

The upper right lateral incisor was tippedat an angle which made it impossible toget it parallel with the other telescopecrowns. Therefore, it was restored with abonded porcelain crown and the palatalside was made parallel with the othertelescopes.

Fig. 14: Inner telescope crowns in position:Telescopes on 23, 26, 13, 14 and the bondedporcelain crown on 12.

Fig. 15: Finally, placing the prosthesis,locating it on the primary inner crowns.

Fig. 16: Prosthesis seen from below. Noticethe two TK1 elements in position.

Fig. 17: The tiny screws are easy to adjustwith a small screwdriver and give strength tothe friction fit of the prosthesis.

Fig. 18: The prosthesis in position.

Fig. 19: No clasps necessary and with a fullarch prosthesis, no problems with colourmatching.

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to treat the abutment teeth at aconvenient time. Also, if a patient has hadto tolerate a temporary acrylic denture fora while then they appreciate the benefitsof the superior telescope crown-retainedprosthesis much more.

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)

ConclusionIncreasingly we are seeing older patientswho have lived through the ‘drill and fill’years of dentistry, who have heavilyrestored mouths and consequently a lackof good tooth structure to work with. Astheir teeth start to fail, the decision onhow to restore their mouths can beincreasingly difficult. I find that a lot ofthese patients do not want to wear adenture and either cannot afford the costof implants or do not like the idea of theinvasive treatment involved with implanttreatment. All general dental practitionerswill have the skills necessary to providethis treatment, so this may save having torefer to an implant specialist. Obviouslycase selection is very important, but I feelthat a telescope crown-retained prosthesiscan be a useful alternative option to offersome of these patients. In the UK this isan option that we often forget to offer.

As the cost of dental treatment increases,patients want to know how longrestorations will last, so they can assess ifthey are going to get good value for theirmoney. As clinicians we know that it isalmost impossible to guarantee anydental work and heavily restored teethtend to be the most unreliable. For me,the fact that the telescope crown-retainedprosthesis is easily removed means that Iam confident that I can sort out aproblem with an abutment toothunderneath. Also, if there are severalabutment teeth available to accept thetelescope crowns, then if one tooth failsand we have to extract it, then usually wedo not lose the whole prosthesis. Theprosthesis will usually hold pretty wellwith one less abutment tooth. So whilst Icannot guarantee that the patient will nothave a problem, I am much moreconfident that I will be able to fix it if ithappens.

I also think that the telescope crown-retained prosthesis can be a bettertransition towards a full denture.

Fig. 20: A successful treatment.

Fig. 21: A satisfied patient.

About the authors

Dr Bernard Martin Mayston BDS London is the principal/owner ofDiss Dental Care Centre.Member of www.norwichden-tistsstudygroup.co.ukDr Mayston has been caring for hispatients in Diss and its surrounding areafor over 28 years.

Dr Bernard Martin MaystonDiss Dental Care Centre, Oxford House127 Victoria Rd, Diss, Norfolk IP22 4JN UKPhone: +44 1379 643 789Email: dissdentalcarecentre@hotmail.co.uk

Ulrich Hekeris the owner-manager of Ulrich HekerDental Laboratory founded in 1996 withthe strap line TEETH ‘R’ US.As a qualified master craftsman (GermanMaster Dental Technician) since 1991, hehas over 26 years’ experience both at thebench and in running a successfulbusiness. Ulrich lives in Mülheim on theriver Ruhr and is an accomplished‘western-style’ rider in his spare time.Ulrich is fluent in English and can becontacted at:

Corneliastr. 17, D-45130 Essen, GermanyPhone: +49 201 797 955Video skype: teeth.are.us Web: http://www.teethrus.deEmail: ulrich@teethrus.de