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I 17 case report _ toothless jaws I CAD/CAM 2_2010 Fig. 8_Good fit with a CAD/CAM-manufactured attachment construction made of pure titanium. The jig must then fit onto the implants in the mouth without causing tension or shifting around. For the exactdeterminationoftheaccuracyofthecastingfit, itisadvisabletoperformtheSheffieldTest.Ascrewis mounted and fastened on the post on one side of the distalimplant.Whenfasteningthescrew,thetransfer jig must not lift off the other implants. Furthermore, there must not be any gaps. If the screw can be fas- tened without making the transfer jig move, it can be concludedthattheimpressionhasexactlycopiedthe situation in the mouth. In case of a negative result, a transfer defect can be assumed. In this case, the transfer jig should be separated and all posts should be fastened with screws so that a new impression casting can be taken. Once an exact impression has been secured and the tooth arrangement has been adjusted, the CAD/ CAM manufacture of the superstructure 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 according to the specifications of the dentist(s) and dental technician(s). In the present case, a bar at- tachment construction made of titanium with distal attachments (Preci-Vertix, CEKA) was chosen. The tooth arrangement determines the space available for the superstructure and alignment to- wards the chewing area. This information then con- stitutes the foundation for CAD of the superstruc- ture, the CAD process. For this purpose, special scan posts are initially screwed onto the implants, in order to determine the position of the implants withafirstscan.Then,asecondscanisdonewiththe waxarrangement,inordertodeterminetheavailable space and the orientation of the superstructure. Thereafter, the desired superstructure is designed with the help of special software. This constitutes the basis for the manufacture of the superstructure utilising the CNC process (Fig. 5). Dental technicians and care providers will then receive the construction suggestion of the Compar- tis ISUS Planning Centre by e-mail with a request for release or for advice regarding changes. As soon as the release is obtained, the manufacture of the attachment begins. The Compartis ISUS system uses moderncuttingmachinesandspecialcuttingstrate- gies and ensures perfect quality of the surfaces, ren- dering manual post-processing dispensable (Fig. 6). The dental laboratory can now commence with the fabrication of the secondary construction. In the presentcase,asecondarystructurewasinitiallymade by means of electroplating (Solaris, DeguDent) and the plastic matrix for the Preci-Vertix retaining ele- ments was incorporated. Thereafter, a cast tertiary structure was made of a Co-Cr alloy and bonded withthegalvanoplasticstructure.Thesuperstructure wascompletedusingtheexistingtootharrangement (Fig.7).Severalinvitroexaminationshaveproventhe excellent accuracy of fit in these CAD/CAM-manu- facturedconstructions(Fig.8).Inacomparisonoffive different techniques for the manufacture of implant superstructures, the CAD/CAM structures demon- strated a median accuracy of fit of 25 µm, while cast structures had median gap widths of 78 µm.13 However, the advantage of the CAD/CAM technology is not only the highly precise manufacture of superstruc- tures made of pure titanium and Co-Cr alloys, but also its applicability to a broad range of indications. Starting from the scan data, virtual construction allows for a wide rangeofvariationsintermsofvariousformsofsuper- structures,fromthesimpleroundbartoretainingele- ment attachments or to a bridge frame for fixed con- structions. With a CAD/CAM system, it is also possible tovirtuallyincorporateactiveholdingelementssuchas extra-coronalretainingjoints,barsandpressbuttons. In summary, it can be said that CAD/CAM tech- nology is also ideal for the processing of alternative materials on titanium and non-precious metal basis. It provides the following advantages: _high mechanical resilience due to homogeneous pore-free materials; _tension-free fit due to precise CNC-manufacturing technology; and _suitability for a large width of indications due to individual CAD. Theintegrationofvirtualdesignsupplementsthe trusted manufacturing technology based on cutting and hence opens up possibilities for new indications foralternativematerialsinimplantprosthodontics._ Editorial note: A complete list of references is available fromthepublisher. Dr Sven Rinke Geleitstr.68 63456 Hanau Germany rinke@ihr-laecheln.com CAD/CAM_contact Fig. 8