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ePaper created 2014-08-26, 21:44:32 | version 1.30.01
I 39 case report _ restoration of atrophied maxillae I CAD/CAM 3_2014 Implants). The dental technician can use the free ATLANTIS ISUS Viewer software in the laboratory to view in 3-D and finalise digitally the bar design proposed by the milling centre. The bar was then milled from cobalt–chromium at the milling cen- tre and the restoration shipped to the dentist’s private laboratory. Owing to the precision of the impression and industrial fabrication, the bar frameworkexhibitedatension-freefitandserved as the basis for fabricating the final superstruc- ture in the laboratory. In the final session, before positioning the finished restoration, the fit of the bar in the pa- tient’s mouth was checked using the Sheffield test.Thefitofthebaragainappearedtensionfree, allowing the bar to be permanently screwed to the implants (Figs. 22–24). The primary splinting of the implants by the bar gives the restoration great stability in the augmented bone in particular. Owing to the uni- form distribution of the implants in the ridge and creation of a large support polygon, good force distribution across the implants is possible, which in turn achieves a good long-term result. Because the bar construction is screw-retained, the risk of leaving excess cement in the peri- implant region, which poses the risk of peri- implantitis and should not be underestimated, according to the latest studies, is avoided.4 The removable palate-free prosthesis is pro- vided with latches (MK1 attachment) on both sides to anchor the prosthesis to the bar firmly. The latches counteract pull-off forces and pre- vent abrasive wear on the bar when the canine guidance is set and the resulting friction loss of the bar-latch design (Figs. 25 & 26). _Conclusion Owingtoprimarysplintingoftheimplantswith a bar construction and the large support polygon created, maximum stability is achieved directly in the augmented bone. In atrophied maxillae, it is often observed that the maxillae are smaller than the mandible owing to centripetal shrinkage. The advantage of the bar restoration over a telescopic restoration with regard to this problem is the de- couplingoftoothandimplantposition.Thebarcan be placed in front of the alveolar ridge and, despite anunfavourableinitialsituation,stillachievegood occlusion and lip support. The bilateral latches for this restoration give the patient direct control of the anchoring of the restoration and thus a feeling of security. In addi- tion, access for cleaning is not affected in any way because the restoration is removable. The use of latches takes into account the patient’s desire for a fixed restoration and the requirement for long- term stability, which is the basis of the easy-to- clean design. Furthermore, the removable restora- tion allows quick and easy repair, and chipping is never an issue because ceramics are not used. Unlike a fixed restoration, no aesthetically or phonetically compromising cleaning channels are required. The cleaning channels of fixed im- plant bridges often make it difficult for patients to form the ‘s’ sound. This can bring into question the success of the entire restoration because it can make the patient feel uncomfortable and in- secure owing to speech impediment. In contrast, the restoration presented here does not affect pronunciation at the buccal plate. Thefinalrestorationexhibitsafunctional,aes- thetically pleasing, and phonetically unimpaired result that meets the patient’s wishes. There- fore, this treatment concept is a good option for restoration of edentulous atrophied maxillae._ Editorial note: A complete list of references is available from the publisher. Fig. 26_The integrated bar-latch restoration. Dr Frank Zastrow is in private practice inWiesloch in Germany.He can be contacted at www.frankzastrow.com. CAD/CAM_about the author Fig. 26 CAD0314_34-39_Zastrow 22.08.14 14:29 Seite 6