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I 19 case report _ CAD/CAM I implants1_2010 nationoftheaccuracyofthecastingfititmakessense to perform the so-called Scheffield test. For this test, a screw is mounted and fastened on the post on one side of the distal implant. When fastening the screw, the transfer jig must not lift off the other implants. Further, there must not be any gaps. If the screw canbefastenedwithoutmakingthetransferjigmove the conclusion can be drawn that the impression has exactlycopiedthesituationinthemouth.Incasethat the test has a negative result a transfer defect can be assumed.Insuchacase,thetransferjigshouldbesep- arated, and all posts should be fastened with screws, so that a new impression casting can be taken. Onceanexactimpressionhasbeensecuredandthe tooth arrangement has been adjusted, the CAD/CAM manufacture of the supraconstruction can begin. First, the work model and the tooth arrangement are sent to a Compartis ISUS Planning Centre. There, the virtual construction of the attachment is made ac- cordingtothespecificationsofthedentist(s)andden- taltechnician(s).Inthepresentcase,abarattachment construction made of titanium with distal attach- ments(Preci-Vertix,CEKAGermany)hasbeenchosen. The tooth arrangement determines the space avail- able for the supraconstruction and the alignment to- wards the chewing area. This information then con- stitutesthefoundationforcomputer-assisteddesign of the supraconstruction, the CAD process. For this purpose, first, special scan posts are screwed into the implants,inordertodeterminethepositionoftheim- plants with a first scan. Then a second scan is done with the wax arrangement, in order to determine the available space and the orientation of the supracon- struction. Then, the desired supraconstruction is de- signed with the help of special software. This consti- tutes the basis for the manufacture of the supracon- struction utilising the CNC process (Fig. 5). Dentaltechniciansandcareproviderswillthenre- ceive the construction suggestion of the Compartis ISUSPlanningCentrebyemailwiththerequestforre- lease or for advice of possibly required changes. As soonasthereleaseisobtainedthemanufactureofthe attachment begins. The Compartis ISUS system en- sures, particularly by applying modern cutting ma- chines and special cutting strategies with all the ma- terials, a perfect quality of the surfaces which dis- pensewiththeneedformanualafter-processingalso asfarastheretainingelementsareconcerned(Fig.6). Then the dental laboratory can commence with the manufacture of the secondary construction. In the present case, first, a secondary structure was madebymeansofelectroplating(Solaris,DeguDent), andtheplasticmatrixforthePreci-Vertixretainingel- ements was incorporated. After that, a cast tertiary structure was made of a cobalt-chromium alloy and bondedwiththegalvanoplasticstructure.Thesupra- construction was completed using the already exist- ingtootharrangement.Severalin-vitroexaminations prove the excellent accuracy of fit in these CAD/CAM manufactured constructions. In a comparison of five different techniques for the manufacture of implant supraconstructions,theCAD/CAMstructuresshowed a median accuracy of fit of 25 µm, while cast struc- tures had median gaps of 78 µm width (Torsello et al. 2008; Fig. 7). However,theadvantageoftheCAD/CAMtechnol- ogy is not only the highly precise manufacture of suprastructuresmadeofpuretitaniumandCo-Cral- loys; there is also its applicability to a broad range of indications. Starting out from the scan data, the vir- tualconstructionallowsforawiderangeofvariations intermsofvariousformsofsupraconstructions,from the simple round bar to retaining element attach- ments or to a bridge frame for fixed constructions. WithaCAD/CAMsystem,itisalsopossibletovirtually incorporate active holding elements such as extra- coronal retaining joints, bars and press buttons. Insummary,itcanbesaidthattheCAD/CAMtech- nology is also ideal for the processing of alternative materials on titanium and NEM basis. It provides these advantages: _Highmechanicalresiliencethankstohomogeneous pore-free materials; _Tension-free fit thanks to precise CNC manufactur- ing technology; _Suitability for a large width of indications thanks to individual computer-assisted design. The integration of the virtual design supplements thetrustedmanufacturingtechnologybasedoncut- ting and hence opens up possibilities of new indica- tions for using alternative materials in implant prosthodontics._ Editorial note: Bibliographical reference is immedi- ately available for download at www.zwp- online.info/fachgebiete/implantologie. Dr med dent Sven Rinke,MSc,MSc Geleitstr.68 63456 Hanau,Germany E-mail:rinke@ihr-laecheln.com _contact implants