**3. Emergence profile**

The ninth edition of the Glossary of Prosthodontic Terms (GPT9) defines 'emergence profile' and 'emergence angle' identically for natural teeth and implant prosthesis [19]. Emergence profile is defined as the contour of a tooth or restoration, such as the crown on a natural tooth, dental implant or dental implant abutment, as it relates to the emergence from circumscribed soft tissues. Emergence angle is the angle between the average tangent of the transitional contour relative to the long axis of a tooth, dental implant or dental implant abutment.

However, extrapolating these words to implant prostheses remains ambiguous at the moment, as there are no established outcome metrics or protocols to support quantitative measurements. Emergence profile and emergence angle are currently defined in terms of 'circumscribed soft tissues'. While these can be clearly characterized and quantified in the relatively narrow periodontal sulcus, they present considerable complications when it comes to implant measurements [20].

The term 'implant supracrestal complex' has been recently proposed in order to describe the anatomic complex of human tissue, mechanical components and bacteria extending through the transmucosal part of an implant prosthesis. The paradigm of the 'implant supracrestal complex' aims to describe the human tissue in parallel with the design features of the implant-abutment-prosthesis complex and assists in identifying the role of design elements in health and disease of the peri-implant tissue [21]. The

review article by Mattheos et al. investigated seven focus questions regarding emergence profile, emergence angle and/or 'implant supracrestal complex' [21]:


The conclusions from this review article can be summarized as follows:


Additionally, the authors state that there are insufficient data with bone-level implants to conclude that a large emergence angle in combination with a convex abutment or prosthesis may result in peri-implantitis. Additional study is necessary to characterize the emerging profile in respect to the real degree of peri-implant soft tissue and to interpret these results more accurately. A single randomized clinical study found no difference in the risk of peri-implant mucositis between tissue- and bone-level implants. Prosthesis modification may be an effective and necessary adjunct to anti-infective therapy for periimplant mucositis in implant-supported prostheses with limited access to oral hygiene. At the moment, there are no data to suggest that increasing the vertical height of the peri-implant soft tissues alone increases the risk of peri-implantitis. However, it has been shown that treating established peri-implant mucositis is more difficult in the presence of a deep peri-implant sulcus. It has not been shown that the presence or absence of a prosthetic abutment, or the material of the abutment (Titanium or Zirconia), alters the risk of peri-implantitis. The evidence relating the kind of prosthesis retained and the risk of developing peri-implantitis is equivocal.

From a clinical standpoint, properly shaped dental implant restorations are critical for the treatment's aesthetics and biological success. The primary challenge is the shift from a round dental implant to the cervical shape of the missing tooth. This transition is accomplished through the use of implant abutments. Su et al. [22] characterized this contour as having two adjacent but distinct zones within the dental implant abutment and crown, an apically located subcritical contour zone and a coronally located critical zone. The critical zone refers to the portion of the dental implant abutment and crown that lies between the free gingival margin and the deeper subcritical zone. This zone is circumferential in form, approximately 1 mm wide in the apicocoronally direction and is often convex or flat in shape. The critical zone may or may not contain a variety of restorative materials, depending on the kind of restoration (cemented or screw-retained). The subcritical zone is positioned apically to the critical zone and may be concave, convex or flat in shape. Changes in the shape of the critical and subcritical contour zones should be planned carefully in accordance with the dental implant site, soft tissue thickness and materials used. If the crown form cannot be

adjusted, reshaping the subcritical zone can improve both the aesthetic and biological success of the treatment.

There are numerous strategies for peri-implant soft tissue conditioning, including immediate temporary restorations, custom-made healing abutments and gradual remodelling of soft tissues through modification of critical and subcritical zones of the temporary implant crown. **Figure 5** shows the emergence profile shaping with custommade temporary PMMA crown on PEEK abutment after the implant was integrated.

In clinical cases like the one shown in **Figure 5**, additional challenge may emerge during copying and transferring emergence profile shape to either digital or conventional stone cast model. In both ways, the clinician needs to act fast due to fast tissue begin to collapse immediately after removing temporary crown (or custom-made healing abutment). In conventional prosthodontics impression, fast and predictable

#### **Figure 5.**

*Emergence profile shaping with temporary PMMA crown on PEEK abutment. Upper-left: initial clinical appearance with stock healing abutment; upper-right: size and shape of soft tissue emergence profile after removal of stock healing abutment; middle-left: lateral view of temporary PMMA crown on PEEK abutment; middle-right: frontal view of temporary PMMA crown on PEEK abutment; lower-left: clinical appearance 2 months after temporary crown delivery; lower-right: newly formed and shaped emergence profile with soft tissue maturation.*

#### *Prosthetic Concepts in Dental Implantology DOI: http://dx.doi.org/10.5772/intechopen.104725*

way is open tray pick-up transfer customization intraorally or extra orally with flowable composite resin material. This technique with intra oral customization with flowable composite resin material is shown in **Figure 6**.

Additionally, the significance of the emergence profile and the interest of clinicians and researchers have increased significantly in recent years. Gomez-Meda et al. [23] defined a more detailed classification of emergence profile surfaces and areas. This article discusses the esthetic biological contour concept (EBC), which consists of distinguishing important zones of emergence profiles and recommending detailed design principles for those zones. The clinical significance of EBC is that it promotes aesthetic outcomes and a favourable biological response to implant-supported restorations when designed properly. The EBC concept denotes three zones that correspond to the subgingival contour of an implant restoration's emergence profile (**Figure 7**). Each of these zones will come into contact with a distinct type of tissue and therefore must be designed differently.

The EBC concept is divided into three zones:

• E Zone (esthetic zone) is a subgingival area that is 1 mm wide and located apical to the free gingival margin. It should be shaped similarly to the crown of the extracted or contralateral tooth to resemble a natural crown. Its contour should be convex and support the free gingival margin in the proper

#### **Figure 6.**

*Left: intraoral customization of open tray pick-up transfer and final impression with preserved emergence profile size and shape for final crown fabrication.*

#### **Figure 7.**

*Schematic presentation of three zones of EBC concept: E—esthetic zone (blue), B—bounded zone (green) and C—crestal zone (red).*

position, establishing the implant crown's cervical morphology. This zone is adjacent to sulcular epithelium, a type of stratified squamous epithelium.


Each of the zones described in the EBC concept serves a distinct purpose in the emergence profile's design. Understanding the significance and unique design features of the EBC zones enables the provision of aesthetic and biologically sound interim and definitive implant restorations.
