Emergence Contours for Single-Unit Implant Provisionals in the Esthetic Zone

The shape of an implant restoration from the point at where it connects to the head of the implant to where it emerges from the soft tissue is commonly called the "emergence contour" (Figure 1 through Figure 3). The specific shape, size, position, texture, and stability of this prosthetic area are critical factors to maximizing the health and esthetics of the peri-implant gingiva. Numerous authors have contributed to the development of guidelines for clinicians' understanding of the peri-implant environment in the provisional and immediate loading stages.^1-13 As practitioners attempt to better understand the prosthetic emergence contours and their effect on tissues, it must be understood that even highly scientific and generalizable guidelines will be limited due to the multiple factors and variables involved with each specific case or study. Nonetheless, it can be beneficial to lean heavily on the expertise of experienced and knowledgeable clinicians for guidance on best practices, protocols, indications, advantages, and limitations.

It is well established that ideal implant selection, position, and placement are the first of many steps toward maximizing the potential for a successful outcome in the esthetic zone. Other factors include:

• appropriate implant depth, generally 3 mm to 4 mm below the desired gingival zenith^9,14-16
• existence or creation of sufficient facial bone and gingiva thickness^{1,3,5,9,12,14-16}
• appropriate implant size for the space (ie, not too wide of an implant diameter) and functional demands of the site (ie, not too narrow)¹⁷
• sufficient implant stability for immediate loading and support of the soft-tissue architecture^18,19 (it is easier to preserve than to recreate)
• adjacent teeth and supporting tissues being in good health

This article focuses on the design of the emergence contours (Figure 1 through Figure 3) for provisional restorations placed at the same time as implant placement (ie, immediate loading). If implant stability or patient compliance are deemed insufficient, the fabrication and use of a custom healing abutment is indicated (Figure 4 through Figure 7). There are significant esthetic and biological gains to be had through the use of an immediate loading protocol, notably preservation or enhancement of the soft tissues.^{1,3,5,6,10-12} However, this procedure is not indicated for every single-tooth implant site. Notably, immediate loading is contraindicated when implant stability is insufficient or functional loads are expected to be excessive. Cautious and thoughtful balancing of the risks and rewards can minimize the chances of implant failure.

Table 1 lists general goals and requirements of the use of a provisional in immediate-loaded single-unit implant treatment. This is a relatively advanced technique and should be executed by an experienced and skilled team. While the use of an immediate-loaded provisional on a single implant is well tested it does produce a slight increase in the risk of implant failure.^20,21 Nonetheless, the use of a well-designed immediate provisional is instrumental in preserving and shaping the soft tissues around the implant. In the authors' experience, without this preservation and shaping, or with poor contours, the soft-tissue form and volume is much more likely to be compromised (Figure 8 through Figure 11).

Surgical requirements for immediate loading have been well established in the scientific literature. They include appropriate implant size, design, and position, sufficient stability (typically tested via torque or implant stability quotient), stable prosthetic connection, systemic and oral health, and patient compliance, just to name some.^2,6,9,10,16

Various abutment materials are available for the intraoral fabrication of an immediate provisional, including titanium, polyether ether ketone (PEEK), and PEEK/titanium hybrids. The authors' clinical preference is to use screw-retained provisionals with titanium temporary abutments because there is no need to use cement and because of their lack of margins, superior seal at the implant-abutment junction, resistance to breakage, and biocompatibility in a wound healing environment. Some key experts, however, have demonstrated repeated exceptional results with PEEK abutments, notably Chu and Kan.^2,3,5,6

There are also many methods and materials that may be used to fabricate and attach the crown form to the abutment. The authors prefer the use of a composite resin shell connected to the titanium temporary abutment with composite. These materials and techniques offer superior strength,^22,23 excellent esthetics, and ease of use in a surgical environment (compared with chemical cure polymethyl methacrylate). However, exceptional results may be achieved with other materials as well, including PEEK abutments,^2,3,5,6 so the miniscule differences between the materials may be of little consequence clinically.

The emergence contour should be smooth and clean before insertion of the crown. The provisional should be appropriately torqued, although care must be exercised to not rotate the implant body during tightening. Anecdotally, 8 Ncm to 12 Ncm has been clinically sufficient for single-unit provisionals. Torqueing to 30 Ncm or 35 Ncm may rotate the implant in immediate placement scenarios. Use of hemostats or forceps to hold the crown portion of the provisional during torqueing will minimize rotational forces to the implant.

Most modern implants in use for single units in the esthetic zone include some degree of a platform-switch design (ie, abutment narrower than implant neck). As such, this creates an initial narrow emergence contour that is already biologically oriented toward a successful outcome. As a general guideline, the emergence contour should emerge from the neck of the implant in a narrow manner that smoothy transitions to the circumference and shape of the tooth at the gingival margin. In the deeper areas of the abutment emergence contour (ie, "subcritical" area) there is no need to add more bulk or thickness of material. This area should be kept as narrow as possible to allow room for biologic graft materials, native tissues, blood clot, and swelling.

In cases of soft-tissue recession beyond what might be esthetically ideal, the use of a provisional with an undercontoured facial surface might be able to rescue the case without the need for additional grafting (Figure 12 through Figure 15). The papilla area (gingival embrasure) should be left open in the provisional during the healing and maturation stages. This will allow the tissues the possibility of migrating to a more favorable coronal position. If the embrasure is closed fully in the healing or maturation stage, it will not be able to migrate to a better position. The provisional must leave space for the tissues. Once the tissues are mature, any remaining open embrasure space can be closed with a longer interproximal contact in the definitive restoration. The provisional should be kept in position without removal for the duration of the integration window (in immediate implant placement) or for 6 weeks for soft-tissue maturation (in delayed implant placement).

The provisional restoration serves as an extremely useful tool to test four key variables in challenging implant treatment: esthetics, phonetics, function, and hygiene. When the emergence contour is properly designed as described here, it is also the most reliable way to allow for the hard and soft tissues around an implant to reach their maximum viable volume and positions (Figure 16 through Figure 23).

Only when the emergence contour of the provisional reaches near the gingival margin should it begin to transition to a wider form. If the deeper area of the abutment emergence is overcontoured it will place excessive pressure into the hard and soft tissues around the implant and may lead to bone loss and gingival recession.^2-4,8,12 In the critical contour area (within 1 mm to 2 mm of the gingival margin), over- and undercontouring can be used to refine the soft-tissue architecture. The amount of refinement of gingival positions possible varies, but it is generally modest. Clinicians should not expect that minor additions or removal of contour will produce drastic results. In cases of severely flattened bone or gingiva around an implant, changes to the emergence contour will generally prove futile in resolving the deficiency.

The slight increase in risk of implant failure due to immediate loading must be weighed carefully against the significant advantage in creating more ideal soft-tissue esthetics. When properly performed, the immediate-load implant protocol can aid clinicians in achieving impressive results. This is contingent on a team of skilled and thoughtful clinicians using this technique only when and where appropriate. (A custom healing abutment is a wise alternative when indicated.) The emergence contour of the provisional is the link between the surgical and prosthodontic workflows, and its proper execution will maximize the likelihood of a successful outcome.

The authors thank Barry P. Levin, DMD, for the invitation to contribute this article, Sam Alawie, MDT, for his talent and expertise in the laboratory support for these clinical cases, and Peter K. Moy, DMD, for his talent and expertise in the surgical stages of the clinical cases in Figure 8 through Figure 11 and Figure 16 through Figure 23.

Todd R. Schoenbaum, DDS, MS
Clinical Professor, Dental College of Georgia at Augusta University, Augusta, Georgia

Young K. Kim, DMD, DMSc
Clinical Assistant Professor, Department of Prosthodontics, New York University College of Dentistry, New York, New York; Private Practice, New York, New York

Faris Khalifa, BDS
Implant Fellow, Tufts University School of Dental Medicine, Boston, Massachusetts