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ePaper created 2017-03-17, 10:24:23 | version 1.38.0
Figs. 5a–c (a) The long axis of the implant corresponds to the incisal edge of the future restoration, allowing a physiological EA. (b) The long axis of the implant corresponds to the cingulum of the future restoration. (c) The implant is placed more palatal, creating an unfavorable undercut that will make very di(cid:3)cult the cement removal. Figs. 6a–c (a) Failing implant-sup- ported porcelain-fused-to- metal crown on tooth #26. (b) Radiographic evalua- tion. (c) The crown removed along with the implant. The presence of undetected cement was the reason for the failure. Fig. 5a Fig. 5b Fig. 5c Fig. 6a Fig. 6b Conventional guidelines for implant placement have been conceived and widely adopted for restorative abutments made with a horizontal preparation (shoulder or chamfer). However, as can be seen in Figure 5, placing an implant with a shoulderless abutment with a cin- gular (Fig. 5b) or palatal (Fig. 5c) position would lead to a crown with an EA and cervical contour far from the anatomical ones described by Wheeler and Du.17, 20 However, when the implant is slightly more buccally positioned, as in Figure 5a, the EA and cervical contour look much more natural and physiological. Currently, there is no evidence that an excessive artificial cervical contour is either beneficial or detrimental to soft- tissue stability, even though, accord- ing to the authors’ clinical experience, some adverse soft-tissue behavior has been noted when such crown contours are designed (Fig. 4f). However, increas- ing the convexity of the subcritical con- tour will create an undercut which will ultimately make cement removal, for a cemented crown restoration, much more difficult. Leaving residual cement inside the gingival sulcus is more likely to occur with restorations such as those illustrated in Figures 5b and c, thus placing the implant at great risk of periimplantitis and possible loss21 (Figs. 6a–c). Whenever a shoulderless preparation is the geometry of choice, it is therefore advisable to change the position of the implant in a more vestibular direction, with the long axis corresponding to the incisal edge of the future restoration or of the adjacent teeth. This position will allow the creation of physiological crown profiles and angles closely re - sembling those of a natural tooth 22 (Figs. 7–9). 60 — issue 2017 Advanced Implant Esthetics Article Fig. 6c