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