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ePaper created 2014-10-07, 09:31:41 | version 1.30.01
special _ 3-D planning for implants I bone topography (Figs. 6a & b). The amount of bone to be removed can be visualised as shown in Figure 7a and then as- sessed with realistic man- ufacturer-specific implant placement in the bone (Fig. 7b). The occlusal and facialviewsrevealthenew width of available crestal bone for implant place- ment (Figs. 8a & b). The visualisation of the bone crest can aid in the deter- mination of ideal implant recipient sites. However, it must be noted that all other views must be con- sidered to appreciate ad- jacent vital anatomical structures and the re- maining topography of the anterior mandible be- fore any plan can be fi- nalised. Several different options can be quickly simulated and then discussed with the patient and all members of the implant team. The use of a bone reduction template can facilitate the accurate removal of bone and the immediate placement of implants, eliminating the need for two separate surgical interventions and thus minimising patient morbidity. The initial plan in the case demonstrated was for the patient to receive an implant-retained overdenture. Therefore, recipient sites were de- termined based upon the available bone in the mandibular symphysis between the right and left mental foramina, which were assessed in the axial and cross-sectional views. While it is possible to fabricate an overdenture design with implants in the posterior region of the mandible, the usual position of implants is within the symphysis re- gion.Thechoicesweretoplacetwoimplants,three implants, or four implants between the two men- talforamina(Figs.9a–d).Thesymphysisareaisnot free from risk. A cross-sectional view is necessary for an appreciation of the thickness of the facial and lingual cortical bone plates, and for assess- ment of the trajectory and topography of the an- terior mandible. In addition, there are important vessels in the region that have been shown to cause severe haemorrhaging if perforated. These vessels may differ from patient to patient and underscore the importance of a 3-D diagnosis. In this case, two such vessels were found in the midline area of the symphysis (red arrows) as seen in the cross-sectional view, which also revealed the extensive bone loss surrounding the hopeless teeth (yellow areas; Fig. 10). Virtual realistic implants were simulated in the residual alveolar bone (Figs. 11a–d). A simulated surgical template was fabricated for the desired implant positions and rested on the reduced bone both facially and lingually. At the midline, where thevitalvesselsresided,itwaselectednottoplace an implant to avoid potential surgical complica- tions (Fig. 12). The simulated bone-borne surgical template was visualised in various 3-D recon- structed volumes (Figs. 13a–c). The first two re- vealed a midline horizontal stabilisation screw (Figs. 13a & b) and the last showed a standard bone-borne template without fixation (Fig. 13c). Had additional implants been required for im- proved stability or had a fixed detachable hybrid restoration been indicated, supplementary recipi- ent sites could have been located based upon the available anatomy. In order to demonstrate the capabilities of the new digital paradigms, five virtual implants were placed into the initial anterior alveolar ridge after the teeth had been extracted virtually (Fig. 14a). The positions of implants can be further en- hanced by placing yellow abutment projections that extend above the occlusal plane. Using se- lective transparency, the various structures can be adjusted in opacity and translucency. Using advanced software simulation, horizontal osteo- I 37cone beam3_2014 Fig. 12Fig. 11dFig. 11c Fig. 11bFig. 11aFig. 10 CBE0314_34-39_Ganz 30.09.14 14:17 Seite 4