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been used in semiconductor tech- nology for a long time. This prop- erty also offers benefits for use in the oral cavity. The pharmaceutical industry uses PEEK in production. Parts in contact with the product are made of PEEK owing to its low discol- orationandhighresistancetowear and corrosion. Both properties are also very useful for dental tech- nology. PEEK is indicated for removable, as well as conditionally removable, prostheses. Therefore, bridges, crowns, telescopic dentures and attachments, as well as screw- retained superstructures, can be fabricated. The material has very good sliding properties and pa- tients report that it is extremely comfortable to wear. There are two different methods of manufacture. One is injection moulding and the other is CAD/CAM milling. The minimum thickness of telescopes is 0.6 mm. The minimum thickness of frame- works and bars is distinctly higher, but varies depending on the de- sign and the size of the telescopic prosthesis, as well as the number of available telescopes. Generally, aPEEKtelescopicprosthesiswillbe a little thicker than a metal tele- scopic prosthesis. It is an absolute necessity that the primary crown be made of zirconia, as abraded metal particles would otherwise collectunderthesecondarycrown. The veneer bond strength was tested in a study at the University of Regensburg, Germany, in 2012. In order to pass the test, a value of 5 MPa had to be achieved. Of all the veneering systems tested, PEEK scored 10 MPa and above and passed all of the bond strength tests. In other tests, such as discol- oration and shear strength, it also achieved very positive results, con- firming the suitability of PEEK for use in the oral cavity. When sub- jected to load at fracture tests, a PEEK bridge achieved 2,354 N and was far su-perior to a ceramic bridge, with 1,702 N. Hence, PEEK can withstand higher loads in the oral cavity than can ceramic mate- rial, and so wide-span telescopic dentures can be made of PEEK. It is necessary when handling telescopic dentures of PEEK to apply ceramic guidelines because the material could otherwise be weakened owing to crack propa- gation. In addition, the prosthetic designmustfollowcertaincriteria. Forexample,aprosthesiswithouta transversebarmustalwaysinclude a backing plate in the secondary part to provide sufficient stability. Dental technicians required to make non-metal telescopic pros- theses should therefore receive sufficient training and instruction so that the required high-quality levelcanbemaintained.Thosewho workwithPEEKonlyrarelyandwho therefore lack experience are ad- visedto have telescopic prostheses of PEEK designed and cut in a spe- cialised laboratory. Even in our laboratory, we have come across PEEK prostheses with cracks, but these have invariably been due to manufacturing mistakes. Prosthe- ses made correctly exhibit no cracks. Cracks and spalls of the veneering of PEEK dentures can be found about as often as in tele- scopicprosthesesofmetal—thatis, rather seldom. PEEK is extremely resistant to plaqueandinerttoacidsandchem- icals; therefore, the denture can be cleaned with a chemical dental cleaner. Frictionisoneofthemostcritical characteristics of telescopic pros- theses. The friction of PEEK is very good and can be controlled ex- cellently with expansion plaster. However, most important is that frictionispermanent.Wemadeour first telescopic prostheses of PEEK about five years ago and we have not observed any loss of friction in that time (Figs.7–13). Conclusion Our laboratory has the experi- enceofhavingmadeover300non- metal telescopic prostheses over the course of 11 years. After initial problems and several tests, PEEK has finally proven a suitable mate- rial for telescopic dentures in the long term. Non-metal telescopic prostheses are in no way inferior to metal telescopic dentures, pro- vided they are made profession- ally. On the contrary, the light weight, the high wear comfort and the absence of metal, in particular, arecompellingargumentsforden- tal technicians and patients alike. 15 Dental TribuneAsia Pacific Edition | 1+2/2016 TRENDS&APPLICATIONS Claudia Herr- mann is owner and CEO of Dental-Labor Herrmann in Bad Tölz in Ger- many. She can be contacted at abt@dl-herrmann.de. Endodontic & Restorative Excellence at the Apex of Africa Christine Berthold (Canada) Elio Berutti (Italy) Arnaldo Castellucci (Italy) Bernard Friedland (USA) James L Guttman (USA) Markus Haapasalo (Canada) Sergio Kuttler (USA) Martin Levin (USA) Tara Mc Mahon (Ireland) Francesco Mangani (Italy) John Meechan (UK) Yoshitsugu Terauchi (Japan) Martin Trope (USA) Peet van der Vyver (South Africa) The South African Society of Endodontics & Aesthetic Dentistry 3-6 June 2016, Cape Town, South Africa www.ifea2016.com SPONSORS SPEAKERS DIAMOND BRONZE SILVER AD DTAP0116_14-15_Hermann 12.02.16 13:00 Seite 2 DTAP0116_14-15_Hermann 12.02.1613:00 Seite 2