implants UK - the journal of oral implantology

I 19implants1_2011 research_ Toothless jaws I Fig.8_Good fit with a CAD/ CAM-manufactured attachment construction made of pure titanum roots Dr Sven Rinke Geleitstr. 68 63456 Hanau Germany rinke@ihr-laecheln.com _contact distal implant. When fastening the screw, the transfer 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 concluded that the impression has exactly copied the situation in the mouth. In case of a negative result, a transfer defect can be assumed. In this case, the transferjigshouldbeseparatedandallpostsshouldbe fastenedwithscrewssothatanewimpressioncasting canbetaken. Onceanexactimpressionhasbeensecuredandthe tooth arrangement has been adjusted, the CAD/ CAM manufactureofthesuperstructurecanbegin. First,the work model and the tooth arrangement are sent to a CompartisISUSPlanningCentre.There,thevirtualcon- struction of the attachment is made according to the specificationsofthedentist(s)anddentaltechnician(s). In the present case, a bar attachment construction madeoftitaniumwithdistalattachments(Preci-Vertix, CEKA)waschosen. Thetootharrangementdeterminesthespaceavail- ableforthesuperstructureandalignmenttowardsthe chewing area. This information then constitutes the foundation for CAD of the superstructure, the CAD process.Forthispurpose,specialscanpostsareinitially screwed onto the implants, in order to determine the positionoftheimplantswithafirstscan.Then,asecond scanisdonewiththewaxarrangement,inordertode- termine the available space and the orientation of the superstructure. Thereafter, the desired superstructure is designed with the help of special software. This con stitutes the basis for the manufacture of the super- structureutilisingtheCNCprocess(Fig.5). Dental technicians and care providers will then receive the construction suggestion of the Compartis ISUS Planning Centre by e-mail with a request for releaseorforadviceregardingchanges.Assoonasthe releaseisobtained,themanufactureoftheattachment begins. The Compartis ISUS system uses modern cut- ting machines and special cutting strategies and en- suresperfectqualityofthesurfaces,renderingmanual post-processingdispensable(Fig.6). The dental laboratory can now commence with the fabrication of the secondary construction. In the present case, a secondary structure was initially made bymeansofelectroplating(Solaris,DeguDent)andthe plastic matrix for the Preci-Vertix retaining elements was incorporated. Thereafter, a cast tertiary structure wasmadeofaCo-Cralloyandbondedwiththegalva- noplasticstructure.Thesuperstructurewascompleted using the existing tooth arrangement (Fig. 7). Several in vitroexaminationshaveproventheexcellentaccuracy of fit in these CAD/CAM-manufactured constructions (Fig. 8). In a comparison of five different techniques for the manufacture of implant superstructures, the CAD/CAM structures demonstrated a median ac- curacyoffitof25μm,whilecaststructureshadmedian gap widths of 78 μm.13 However, the advantage of the CAD/CAM technol- ogy is not only the highly precise manufacture of su- perstructuresmadeofpuretitaniumandCo-Cralloys, butalsoitsapplicabilitytoabroadrangeofindications. Starting from the scan data, virtual construction al- lows for a wide range of variations in terms of various forms of superstructures, from the simple round bar to retaining element attachments or to a bridge frame for fixed constructions. With a CAD/CAM system, it is also possible to virtually incorporate active holding elements such as extra-coronal retaining joints, bars andpressbuttons. In summary, it can be said that CAD/CAM tech - nology is also ideal for the processing of alternative materialsontitaniumandnon-preciousmetalbasis.It providesthefollowingadvantages: _highmechanicalresilienceduetohomogeneous pore-freematerials; _tension-freefitduetopreciseCNC-manufacturing technology;and _suitabilityforalargewidthofindicationsdueto individualCAD. The integration of virtual design supplements the trusted manufacturing technology based on cutting and hence opens up possibilities for new indications foralternativematerialsinimplantprosthodontics._ Editorialnote:Acompletelistofreferencesisavail- ablefromthepublisher. Fig. 8