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IMPLANT POSITION IN THE ESTHETIC ZONE<br />
of the implant position can be manifested in the four<br />
dimensionally sensitive positioning criteria: mesiodistal,<br />
labiolingual, and apico-coronal location, as well as implant<br />
angulation. 3 The ultimate goal is not only to avoid adjacent<br />
sensitive structures, but to respect the biological principles<br />
that have been established to achieve esthetic results.<br />
MESIODISTAL CRITERIA<br />
Correct implant position in a mesiodistal orientation allows<br />
the clinician to avoid iatrogenic damage to adjacent critical<br />
structures. Maintaining adequate distance from adjacent<br />
teeth also helps preserve crestal bone and interproximal<br />
papillary height. When placing an implant adjacent to a<br />
tooth, it has been shown that crestal bone peak is based on<br />
and maintained by the bone level of the teeth adjacent to<br />
the missing space. A minimum distance of 1.5 mm between<br />
implant and existing dentition has been determined to<br />
prevent damage to the adjacent teeth and to provide proper<br />
osseointegration and gingival contours 4–6 (Fig. 1a). Implants<br />
placed too closely together can reduce the height of the<br />
inter-implant bone crest, and a distance of less than 3 mm<br />
between two adjacent implants leads to increased bone<br />
loss. It has been shown that a distance of more than 3 mm<br />
between two adjacent implants preserves the interproximal<br />
bone peak and results in 0.45 mm of resorption on average,<br />
giving a better chance of proper interproximal papillary<br />
height (Fig. 1b). If the space between implants is 3 mm<br />
or less, the average resorption of the interproximal bone<br />
peak increases to 1.04 mm, compromising support for the<br />
interdental papilla. 4,7 As a result, wide-bodied implants less<br />
than 3 mm apart in the esthetic zone would compromise<br />
the desired outcome.<br />
LABIOLINGUAL CRITERIA<br />
Labiolingual implant position is often determined by the<br />
gingival biotype, occlusal considerations of opposing teeth,<br />
and desired emergence profile. An implant placed too far<br />
labially can cause bone dehiscence and gingival recession<br />
leading to exposure or show-through of the implant collar.<br />
An implant placed too far lingually can cause prosthetic<br />
difficulties with ridge-lap restorations that can be unhygienic<br />
and unesthetic. A thickness of 1.8 mm of labial bone has<br />
been determined to be critical in maintaining an implant soft<br />
tissue profile and increasing the likelihood of an esthetic<br />
outcome 8 (Fig. 2). Labially oriented implants compromise<br />
the subgingival emergence profile development, creating<br />
long crowns and misalignment of the collar with respect to<br />
the adjacent teeth. 9<br />
APICO-CORONAL CRITERIA<br />
Peri-implant crestal bone stability plays a critical role in the<br />
presence of interdental papilla. 10 Many factors contribute<br />
to crestal bone resorption, including existing anatomy, surgical<br />
trauma, overloading, peri-implantitis, implant surface<br />
characteristics, microgap at the implant-abutment junction,<br />
Figure 1a: Minimum distance of 1.5 mm between implant and existing dentition<br />
Figure 1b: Minimum distance of 3 mm between two adjacent implants<br />
Figure 2: Proper labiolingual placement with 1.8 mm thickness of labial bone<br />
28<br />
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