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ePaper created 2014-11-20, 16:14:55 | version 1.30.01
case report _ double crowns I I 23CAD/CAM 4_2014 joints etc. Since the original material has a dark colour, it initially appeared to be not suitable for dental appli- cations. However, one succeeded to vary the colour of the material so that it could also be used for temporary restorations and abutments(Kirsch,2002). Todaythefollowingindicationsare cited: full crown caps for single crown copings, full anatomical bridges, scaf- folds for veneer bridges, primary crowns,inlays,inlaybridgesandMary- landbridges.Sofar,theapprovalofthe material was limited to removable or conditionally removable (screwed) dentures.Thismeansthatwiththede- scribed material metal-free dentures, secondary parts, over structures with combined dentures, implant-sup- ported full crowns in the posterior re- gion and conditionally removable, screw-retained bridgescanberealised. AdistinctionhastobemadebetweenpurePEEKand PEEK with additives. Recently, industrially manufac- turedblanks(Fig.4)areavailablewithanauthorization fordefinitiveandremovabledentures(e.g.dentaldiscs “Tizian PEEK Blanks” Schütz Dental Ltd., Germany). The material has no additives and is used in medicine for manyyearsnow.Sincethehighlypure PEEK material contains no additives— suchasbariumsulfate—itisnotvisible on X-ray control images (Fig. 6). Other manufacturers,however,useadditives such as barium sulfate deliberately for aradiographicdisplay. Also, a so-called white-PEEK is of- fered in the field of dental prosthetics from different companies. This mate- rialismixedwithupto20percenttita- nium dioxide which makes the colour lighter or whitish. In this method, the hardness(flexuralstrength)ofthema- terialisraised,butatthesametimethe sliding property is deteriorated. An- other disadvantage is that from the material titanium dioxideionsgoinsolutionandworklikeaventilationel- ementafteracertainperiodofwear.Thiscanleadtodis- colouration of the gingiva. Therefore, pure, medical PEEK for prosthetic parts processing is rather recom- mended. Fig. 7 Fig. 8bFig. 8a Fig. 6a Fig. 6cFig. 6b Fig. 3a Fig. 3b Fig. 5 Fig. 4 Figs. 3a & b_Full denture with Teflon secondary crowns (Vollmer, R. & Vollmer, M. 1996). Fig. 4_PEEK prosthetic parts milled from so-called blanks (dental discs Tizian PEEK Blank, Schütz Dental Ltd., Germany). Fig. 5_Applications of PEEK in the human body (Source: elements 39, issue 2/2012). Figs. 6a–c_CNC machined PEEK abutment (Dental lab/milling center Anger, Remagen, Germany). No radiological visibility of the PEEK secondary part. Fig. 7_Prefabricated primary parts of different angulations (Schütz Dental Company Ltd., Rosbach, Germany). Figs. 8a–c_Clinical situation with more severe atrophy of the mandible in the posterior region (a); production of total mandibular denture before implant exposure (b); marking the implant positions (c). CAD0414_20-30_Vollmer 14.11.14 13:37 Seite 3 CAD0414_20-30_Vollmer 14.11.1413:37 Seite 3