What Are the Keys to Managing the Gingival Margins for Esthetic Implant Crowns?

Many guidelines exist in the literature regarding implant placement and management of the implant site. By following these guidelines clinicians can improve the predictability of developing desired FGMs. The faciolingual angulation of the implant should be through or palatal to the incisal edge of the restoration. The mesiodistal angulation should be parallel to adjacent teeth or implants. The buccal bone thickness should be no less than 2 mm to preserve vertical bone height and minimize the risk of midfacial recession.¹

Facial bone deficiencies should be treated with regenerative therapies. Repeated surgical interventions, however, have been associated with decreased papillary height.² Non-platform-switched implants should be placed 1.5 mm to 2 mm from adjacent teeth. The prosthetic platform should be placed at least 3 mm below the intended position of the zenith of the FGM. The minimum distance between non-platform-switched implants is 3 mm.³ Platform-switched implants may be closer.⁴ Applying these protocols should create a bone and implant foundation that will support an esthetic soft-tissue architecture.

Attention to detail with respect to handling the soft tissues is critical. Thin periodontal phenotypes tend to have shorter interdental papillae (IDP) than thicker phenotypes following single-tooth implant placement. Minimally invasive surgical techniques, including atraumatic extraction and immediate implant placement, protect the IDP and can limit treatment to only one surgical intervention. When the soft-tissue architecture is inadequate, grafting becomes necessary. Connective tissue grafting can be used to convert thin phenotypes to thick ones and minimize potential apical movement of the FGM. Tunneling soft-tissue grafting techniques protect the IDP and enhance the esthetic results.^5,6Periodontal probing depths of 2.5 mm to 4 mm should provide enough vertical distance to develop an esthetic EP.

Ideal surgical management is not sufficient to successfully manage the FGM. The final outcome is determined by the EP of the restoration. The use of custom abutments and provisional restorations can be extremely beneficial in the development of a stable and pleasing soft-tissue architecture. A concave facial EP promotes increased tissue volume and a stable FGM. Conversely, a prominent and convex facial EP results in the apical movement of the FGM. The interproximal contours should resemble those of a natural tooth and promote the presence of an IDP that fills the embrasure space.

In summary, a natural-appearing soft-tissue architecture is essential for an esthetic implant restoration. Stable FGMs are the result of thoughtful planning and proper management of the implant site. Expertise in both the surgical and restorative phases of treatment is needed to achieve predictable outcomes.

Achieving satisfactory esthetic and functional outcomes with dental implant restorations in the esthetic zone is dependent on, but not limited to, a variety of factors, including appropriate 3-dimensional implant body positioning, adequate soft-tissue volume, a provisionalization phase for tissue profile development, the emergence profile (EP), and definitive restorative considerations.

To attain stable hard tissue and sufficient soft tissue to manage and manipulate restoratively, bone-level-designed implants need to be positioned at least 3 mm apical to the future midfacial gingival margin and lingually to maintain a minimum of 1.8 mm of bone facial to the implant platform (prosthetic screw access in the cingulum/incisal edge area of the future restoration). Implants need to be positioned 1.5 mm to 2 mm from adjacent teeth and adjacent implant restorative platforms, 3 mm apart to achieve interproximal soft-tissue volume and peaks that resemble the shape of natural interdental papillae.^7-11 Implants with an internal/conical connection and platform switch placed 2 mm apart have demonstrated stable interproximal bone levels.^12,13 However, if the interproximal restorative platforms/abutments are less than 3 mm apart, the soft-tissue begins to flatten out, losing its triangular peak and architecture.

By avoiding adjacent implants in the anterior zone, except for the central incisor positions, clinicians can minimize the unpredictability of developing interproximal peaks of soft tissue. Other strategies such as interproximal partial root extraction therapies have recently been reported to aid in the maintenance of interproximal tissue peaks between adjacent anterior implants.^14,15

Development of the EP at the outset with a provisionalization phase is critical in shaping soft-tissue profiles and also maintaining crestal bone levels around dental implant platforms. Excessive emergence direct from the implant platform may result in remodeling of the circumferential implant-bone interface (bone resorption) to accommodate adequate connective tissue and epithelium around an overcontoured abutment. Adherence to a "zero-to-minimal" EP for the first 1 mm to 1.5 mm of the restorative abutment as it exits the implant platform from provisionalization to definitive abutment is critical to maximize the biologic width potential of the implant platform design and implant-restorative interface, thereby maintaining hard- and soft-tissue stability.

Soft-tissue architecture around an appropriately positioned implant body is determined by the shape and volume of the abutment within the tissue cuff. Change to the overall tissue profile can be affected by modification of the last 1.5 mm of the submergence abutment/crown profile as it exits the tissue cuff. Adding or removing contour will affect change of soft-tissue profile, both interproximally and faciolingually. This, in combination with a zero-to-minimal emergence for the first 1 mm to 1.5 mm often results in a desired modified "S"-shaped facial abutment/crown profile.

After appropriate soft-tissue profiles and architecture are achieved in the provisional phase, material selection for the definitive restoration will be based on which material allows for identical EP considerations depending on the implant system used. Screw-retained designs are preferred over intraoral cemented restorations to minimize the potential for iatrogenic-induced peri-implantitis from excess luting cement.

Esthetic parameters for implant restorations are based on many variables beginning with ideal surgical planning and placement of the implant. For the restorative dentist, who serves as the quarterback of the team, the most critical factors are: (1) pre-assessment, which comprises an analysis of the patient's risk factors, including the patient's general health, habits, lip position, lip mobility, periodontium, and shape and position of the adjacent teeth; (2) impression-making; and (3) the provisional and final restorations.

Pre-assessment determines the level of risk for esthetics. Patients with comorbidities, poor oral hygiene, and/or smoking are at higher risk. High lip mobility and short lip length also create increased risk. Assessment of the existing periodontium by sounding to bone is critical. The distance from the facial osseous crest to the free gingival margin ideally should be 3 mm or less. This results in minimal bone loss with careful extraction and at least 1 mm of facial bone thickness.¹⁶If this distance measures more than 3 mm, bone loss can be expected. The interproximal bone should be about 4 mm; this is measured on the adjacent tooth, not the tooth to be extracted. A depth of more than 4 mm will result in papilla loss and black triangles.¹⁷

Tooth shape also influences the position and volume of the interproximal gingiva. Normal and square teeth are the most forgiving, while triangular-shaped teeth, with more incisal interproximal contacts, are more difficult to manage, as black triangle issues often result. This can be resolved by restoratively treating the adjacent teeth.

As part of pre-assessment, photography is critical. Den­tists need to record, eval­uate, and discuss esthetics prior to performing any treatment, and patients' expectations must be addressed preoperatively.

The choice of provisional restoration is another restorative key. The space may be managed in either a fixed or removable manner during the integration phase. A fixed provisional is preferable to maintain the existing tissue profile; healing is more predictable because the loss and reshaping of the tissue is minimized. Undercontouring of the provisional at the gingival emergence profile area will help prevent migration of tissue in the cervical area during healing. The provisional serves as both an esthetic template for the final restorative prosthesis and a communication tool for the laboratory and patient. Since the papilla is supported by the bone on the adjacent tooth, it may still take at least 3 to 12 months to fill into the embrasure space.

Finally, proper impression-making is crucial. In my experience, the open-tray pick-up coping technique is superior to the closed-tray pick-up coping technique. My goal is to accurately replicate the volume and position of the tissue and keep it at a level that matches the other teeth in the esthetic zone. If there is concern about accurately capturing the volume of tissue space, the impression coping may be lined and cured with flowable composite before proceeding to impression-making.

Douglas H. Mahn, DDS
Private Practice limited to Periodontics and Implantology, Manassas, Virginia

Aldo Leopardi, BDS, DDS, MS
Private Practice limited to Prosthodontics, Greenwood Village, Colorado

Rena Vakay, DDS
Clinical Instructor, Kois Center, Seattle, Washington; Member, American Academy of Restorative Dentistry; Accredited Member, American Academy of Cosmetic Dentistry; Private Practice, Centreville, Virginia