IM0110

I 17 case report _ CAD/CAM I implants1_2010 supraconstructions guarantee high patient satisfac- tion. Thanks to their low rate of technical complica- tions,theyrequirelessmaintenanceeffortthanalter- native fitting elements (MacEntee et al. 2005), which isanimportantcriterionforthelong-termsuccessof the prosthesis. High maintenance requirements re- quire more practice visits and take the time of both, the patient and the care provider. Further, if there are technicalcomplicationsthathaveledtothefailureof supra construction elements, an intervention by a dental technician might be needed for the new con- struction or the replacement of individual compo- nents. This is also connected with further costs in order to maintain the function. When evaluating overdenture attachment con- structions as fitting means, consideration must be giventothevarioustypesandformsthereare.Onthe one hand, there are individually shaped bar attach- ments, and on the other hand, there is the classic roundbar,whichcanbemanufacturedeitherbycast- ing or by combination of pre-fabricated elements. The overdenture attachment sitting on four im- plantsisaclassicfittingelementforapurelyimplant- supported coverdenture prosthesis in a toothless upper or lower jaw. A retrospective study with 51 pa- tients compared individually shaped bar attachments and round bars for the fitting of coverdenture pros- theses (Krennmair et al.2008). 26 patients were equipped with round bars, while 25 patients received a supraconstruction with an individual bar attach- ment, on four implants each. After a surveillance pe- riodoffiveyears,thesurvivalrateoftheimplantswas 100%.Largertechnicalcomplications,whichrequired a renewal of the mounting elements, occurred in the round bars only, in form of fractures in the extension areas.Thefracturesontheextensionsoftheoverden- ture attachments, which were exposed to high me- chanicalstress,weredueeithertoporositiesinthecast object,ortoinhomogeneitiesintheareaofthepoints of attachment. Further, it was determined that low- gradecomplications(activationofhanks)wouldcome up three times as often in the round bars as in the bar attachments. Basically, two causes of defects can be derived from that: Firstly, defects due to faults in the manufacturing technique (casting and joining processes), and secondly, defect causatively con- nected with the design of the supra-construction. For the fitting of attachments in the toothless up- per jaw, the literature describes two versions. The fit- ting of attachments on four implants in the anterior segment, and the fitting of two attachments on three tofourimplantsonthelateralsegmentsofthetooth- lessupperjaw(mostlyafteraprevioussinusflooraug- mentation).Alsofortheapplicationofattachmentsin thetoothlessupperjawdatafromclinicalstudieshave been published (Krennmair et al. 2008). Both attach- mentconceptsfeaturedalmostidenticalsurvivalrates afterfiveyears—98.4%fortheattachmentsinthean- terior segment, and 97.4% for the attachment fitting on six to eight implants in the lateral segments of the upper jaw. In particular the fitting by bar attachments seems tobeatherapymeanswithguaranteedsuccessforthe fitting of purely implant-supported coverdenture prostheticsintheupperandlowerjaw.Itexcelswitha lowrateoftechnicalcomplicationsand,withthat,low maintenance requirements. Hence, bar attachments constitute clinically tested fitting elements for im- plant-retained and implant-fitted removable supra- constructions in the toothless upper and lower jaw. Clinical data for the fitting of removable supra-con- structions in the toothless upper jaw are missing for magnetsaswellasforball-headattachments.Alsothe application of so-called locators for the fitting of re- movable implant supraconstructions cannot be con- sideredtobebasedonevidence,accordingtothecur- rentdataprovided,asnoresultsofclinicalstudieshave been presented by now for this fitting element. Telescopes as fitting elements for removable supraconstructions are popular particularly in the German-speakingcountries,astheyareveryhygienic and easy to expand. However, these advantages are opposedbythehightechnicalrequirementsandcosts at manufacture. Clinical studies on the suitability of double crowns as fitting elements in implant pros- theticsshowthattheyaregenerallysuitable,andthey point out the advantage of combining the natural teethwithimplantsforthefittingofaremovablecon- struction, as opposed to attachments. Fig. 2_Fracture of a bar attachment construction manufactured by cast- ing, in the area of the extension. Fig. 3_Casting of the implants in the pick-up technique with a high- strength casting material. Fig. 4_Tooth arrangement produced on the work model. Fig. 5_Virtual construction of the bar attachment construction with distal attachments. Fig. 2 Fig. 3 Fig. 4 Fig. 5