The Implant Supracrestal Complex and its significance for long term
successful clinical outcomes
Published in: International Journal of Prosthodontics, January 2021
Mattheos N 1,2, Vergoullis I 3,, Janda M 4, Miselli A 5.
1. Department of Oral and Maxillofacial Surgery, Faculty of dentistry Chulalongkorn
university, Bangkok, Thailand
2. Department of Dental Medicine, Karolinska Institute, Sweden
3. Department of Periodontics, Louisiana State University, USA
4. Department of Prosthodontics, Malmö University, Malmö, Sweden
5. Department of Prosthodontics, Universidad Central de Venezuela, Caracas, Venezuela
Corresponding author: Nikos Mattheos, DDS. MASc, Ph.D.
Department of Oral and Maxillofacial Surgery, Faculty of dentistry, Chulalongkorn University,
34 Henri Dunant Road, Wangmai, Patumwan, Bangkok, Thailand 10330
Keywords: implantology, peri-implant tissues, implant supra-crestal complex, implant
DO I: 10.11607/ijp.7201
Emerging evidence points towards significant interrelations between the condition of the peri-
implant tissue and the implant-abutment-prosthesis complex. A new paradigm is essential,
where the peri-implant tissues will be studied in close interrelation with the implant, abutment
and prosthesis complex, under the presence of oral biofilm. The aim of this paper is to introduce
the concept of the “Implant Supra-crestal Complex” (ISC) and describe the critical elements
that define it as a unique anatomic, and functional system of human tissues, mechanical
components and oral bacteria / biofilm. The paper reviews recent evidence to identify the
impact of design features on both short-term clinical outcomes, as well as on the long-term
health of the peri-implant bone and soft tissues. Prosthetic-driven implant placement is the
prerequisite for the proper design of the ISC, which in turn can indirectly influence the structure
and dimensions of the peri-implant soft tissues. Design features of the implant-prosthesis-
abutment complex such as the Emergence Profile (EP), Emergence Angle (EA) and Cervical
Margin (CM), as well as the design of the implant-abutment and abutment-prosthesis junctions
and their location in relation to the tissues of the ISC can have significant impact in the
maintenance of stable and healthy peri-implant tissues in the long term.
A multitude of terms has been utilised to describe the peri-implant tissue coronal to the
marginal bone. Initial terms were a direct extrapolation of periodontal terms from the concept
of the “Biologic Width” (1) to the recently introduced “Supracrestal Tissue Attachment” (2).
The significant anatomic and structural differences however between periodontal and peri-
implant tissues, (with the latter displaying “attachment” only at the level of the junctional
epithelium), do not allow for a direct extrapolation of terms from the periodontium.
Consequently, the terms “Peri-Implant Soft Tissue Barrier” (3), “Peri-implant Mucosa” (4),
“Implant Mucosal Tunnel” (5) and most recently the specific “Peri-implant Phenotype” (6)
have been suggested to describe the peri-implant tissues.
Although such definitions appear adequate to describe the soft peri-implant tissues, there is an
increasing body of evidence pointing towards significant interrelations between the condition
of the peri-implant tissue and the implant-abutment-prosthesis complex, all this under the
constant presence of oral bacteria. Emerging evidence suggests that factors such as the type of
implant-abutment junction and prosthesis design and retention can have significant influence
on both short-term clinical outcomes as well as the long-term health of the peri-implant bone
and soft tissues (7,8).
Consequently, a new paradigm is essential, where the peri-implant tissues will be studied in
close interrelation with the implant, abutment and prosthesis complex, under the presence of
oral biofilm, as one multi-element, anatomic and functional unit. In such a system of close
anatomic and functional interaction of the mechanical components and the human tissues,
deficiencies or problems in one of the parts might manifest problems clinically through
complications in any of the other. Such a paradigm is well aligned with the emerging concept
of health and chronic disease being perceived as Symbiosis or Dysbiosis, the outcome of
complex interactions between human, tissues medical devices such as dental implants and
The aim of this paper is to introduce the concept of the “Implant Supra-crestal Complex” (ISC)
and describe the critical elements that define it as a unique anatomic and functional system of
human tissues, mechanical components and oral bacteria / biofilm. Furthermore, this paper
aims to review the current evidence on critical design features of the Implant Supracrestal
Complex, which can contribute to long term sustainable and healthy outcomes or introduce
A. Anatomy and components of the Implant transmucosal complex.
The anatomic structures of the human tissues, the mechanical components of the Implant,
abutment and prosthesis and the oral bacteria are closely interrelated towards maintaining
health, as expressed through clinically stable long-term outcomes. In this capacity, the Implant
Supracrestal Complex displays elements of homeostatic regulation and the tissues of the ISC,
are in close anatomic and functional relation to mechanical components through the interface
of osseointegration and epithelial attachment. Homeostasis can be thought of as a dynamic
equilibrium rather than a constant, unchanging state, where tissues and cells respond to
constant internal and external changes in order to maintain long term anatomic integrity and
1) Anatomic structures of human tissues in the ISC
From apical to coronal in vertical direction, the tissues of the Implant Supra-crestal Complex
are defined by the Marginal Bone (MB), the Connective Tissue (CT), the Junctional Epithelium
(JE) and the Sulcus (S) with the sulcular epithelium.
CT in implants appear with no vascular supply close to the abutment and very few fibroblasts,
resembling more a scar tissue; this is likely attributed to lack of the PDL vascular complex (3).
Blood vessels originating from the supra-periosteal complex are located in the lateral borders
of CT and JE zone. These blood vessels are the origin of the immune response to bacteria in
the sulcus (12,13). Similar to teeth, peri-implant crevicular fluid is produced, which flows into
the sulcus through the junctional epithelium. Analysis of peri-implant crevicular fluid (PICF)
for protein biomarkers such as pro-inflammatory cytokines, chemokines and bone turnover
markers can reveal clinical and sub-clinical inflammation (14).
Although the great majority of histomorphometry available comes from animal studies, human
studies point to the zone of the connective tissue and the junctional epithelium occupying
between 3 and 4.5 mm (3,15) in a vertical dimension. This zone previously called “Biologic
Zone” or “Biologic Width” (3) might be genetically determined. Although individual studies
have suggested small differences in the dimensions of the JE and CT dimensions when different
surfaces were used (3, 16), or when 2-piece were compared with one-piece implants (17), at
present no intervention, surface or implant design has been shown to predictably achieve any
morphological or structural changes of these tissues (18,19). As with all anatomic structures it
is reasonable to assume that the dimensions of the CT and JE could present with natural, limited
variation between different individuals, different anatomic locations (20) or sites of the peri-
In contrast to the JE-CT zone, the peri-implant sulcus varies significantly in depth depending
on the local anatomy, the implant position, or between different sites around the same implant,
especially in the anterior maxilla (21,22). Unlike natural teeth, where the healthy sulcus extends
between 0.5-1.5 mm in depth, peri-implant sites might present with much deeper sulcus. The
natural scalloping of the gingival tissues observed around teeth is a result of the corresponding
scalloping of the underlying bone and the corresponding shape of the cementoenamel junction
(Figure 1). Such scalloping of the tissues has not been possible to maintain around implants
and the use of scalloped dental implant resulted in increased bone loss (23). Consequently, the
scalloping of peri-implant soft tissues - primarily pronounced in the aesthetic zone - is only
possible with a peri-implant sulcus depth of 3-5 mm at interproximal sites, while the same in
the buccal sites of the implant could be as little as 0.5-1.5 mm. It is therefore evident that the
concept of Supracrestal Attachment as described around natural teeth cannot be applied to the
peri-implant tissues. Similarly, a peri-implant sulcus deeper than 3 mm is not to be confused
with a periodontal pocket. The former is the outcome of tissue healing around a clean
biomaterial surface, while the latter is the result of slow apical migration of the junctional
epithelium, due to the challenge of biofilm induced chronic inflammation.
Taking into consideration the above information it becomes important to establish a minimum
peri-implant supra-crestal vertical tissue height of about 3 to 4.5 mm which will accommodate
adequately the biologic demands of sustainable health. In cases where the vertical height of the
peri-implant tissue is less than 3mm, marginal bone resorption has been often reported around
the implant platform. This might be a physiological remodeling, resulting in re-establishing the
vertical dimensions required to accommodate the soft tissues at the expense of the crestal peri-
implant bone. Several researchers have correlated this pattern of early bone resorption, to the
pre-operative supra-crestal gingival tissue height (24-25).
2) Characteristics of Implant – Abutment – Prosthesis
The critical design characteristics of the Implant-abutment-prosthesis complex (IAP), which
have been shown to impact the configuration of the peri-implant marginal bone and soft tissues,
will be discussed separately for Bone level and Tissue Level implants. As Tissue level implants
the authors consider all implants with a smooth transmucosal collar which varies from 0.5 to 3
mm in vertical height. Bone level implants on the other hand are implants without a
transmucosal part and which are intended to be placed with bone contact for their entire length ,
while the transmucosal part is facilitated through a detachable abutment. Furthermore, as
Platform Switching is defined a horizontal discrepancy between the diameter of the implant
shoulder of bone level implants and the diameter of the corresponding abutment (26).
Two critical design features of the IAP intended to be in close contact with the peri-implant
soft tissues are the Emergence profile (EP) and the Cervical Margin (CM). The shape, position
and dimensions of both the EP and CM could significantly influence the short as well as long-
term outcomes of implant treatment.
Furthermore, the IAP contains two important interfaces, the Implant-abutment junction (IAJ)
and the abutment-prosthesis junction (APJ).
Understanding the influence such design choices can have on the healing and the long-term
configuration of the bone and soft tissues is essential for successful clinical outcomes.
i. Emergence Profile (EP)
The term Emergence Profile (EP) is defined in the 9th edition of the Glossary of Prosthodontic
terms 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”. No differentiation is being made in this definition with regards to implants and teeth,
while the emphasis is placed in its interrelation with the “circumscribed soft tissues”. For the
purpose of this paper and based on the implant literature so far, we would further define the EP
as the entire transmucosal part of the IAP, which extends from the most coronal part of the
peri-implant mucosa to the implant platform of a bone level implant, or to the most coronal
intraosseous segment for the Tissue level implant respectively (Figure 1). In the case of Tissue
Level implants, the soft tissue collar of the implant constitutes the apical end of the emergence
profile. The function of the emergence profile is to ensure a proper transition from the implant
to the Cervical Margin, while allowing for adequate space for the peri-implant tissues.
Emergence Angle likewise, was defined as “the angle between the average tangent of the
transitional contour relative to the long axis of a tooth, dental implant, or dental implant
abutment.” Emergence Angle has been initially defined on natural teeth and was calculated by
bringing the tangent line on the crown to the point corresponding to the gingival margin. Thus
as defined on natural teeth, EA presented the angle of the tooth or prosthesis crown at the exact
“point of emergence” through the gingival tissues (27,28).
Two recent studies (7,29) have measured the EA mesial and distal of implant restorations,
using periapical radiographs. The major limitation of the radiographs however is that it does
not allow for estimation of the soft tissue margin, thus calculation of the EA was conducted
without any relevance to the actual “point of emergence”, which was invisible in the
radiographs. Instead, two points were defined, one in the shoulder of the bone level implant or
the collar of the tissue level implant and a second in a selected point of the profile of the
prosthesis and the tangent line was drawn. The clinical relevance of defining the emergence
angle in this manner and what does it actually represent remains to be further clarified. Such
measurements include a significant risk of subjective judgement, as the convexity or concavity
of the emergence profile might influence the position of the second point and consequently the
tangent line. Furthermore, the true emergence and level of the soft tissues is not considered in
the calculation of the EA, which might reduce the clinical relevance. Finally, when
measurement is conducted on tissue level implants the first point is placed in a different
location of the supracrestal complex than when in bone level implants, which could also
seriously affect the calculation of the EA.
Bone level implants allow for the design of the emergence profile in its entirety and the angle
of the emergence can be determined by the prosthetic abutment. Although “prefabricated” or
“catalogue” abutments offer very little variation of the Emergence profile, current CAD/CAM
custom made abutments allow for individual design of critical elements such as emergence
angle and convexity/concavity. Even prefabricated abutments today in many implant systems
come with different cuff height, thus allowing the selection of different angles for the
Emergence profile. The additional ability of platform switching on bone level implants
facilitates further customisation of the EP.
The Emergence profile of Tissue level implants starts with the implant smooth collar, which
corresponds to the apical part of the abutment of bone level implants. This smooth collar
provides the surface for CT adhesion and, depending on height of collar, possibly the whole or
part of the JE attachment. Both the angle and height of the soft tissue collar varies significantly
between different implant systems, or even implants of different types within the same system.
Consequently, the design of the Emergence Profile is predetermined for the most apical couple
of millimetres, as height and angle is defined by the design and dimension the soft tissue collar.
This prefabricated microgeometry together with the lack of platform switching could limit our
options when designing the Emergence Profile in such implants. Two studies (7,29)
investigating the impact of the Emergence Profile in Peri-implantitis prevalence, have however
excluded the transmucosal collar when calculating the Emergence Angle in Tissue Level
implant reconstructions. This might lead to inconsistency when attempting to assess the impact
of the Emergence Profile between Bone and Tissue level implants.
ii) Cervical Margin
The term Cervical Margin of the Prosthesis (CM) refers to the circumferential margin where
the most coronal border of the peri-implant mucosa receives the most apical visible portion of
the prosthesis or “cervix”. Terms as “restoration contour” or “soft tissue contour” have been
used interchangeably in the past to describe this margin. The authors however would like to
emphasize that the term Cervical Margin is a feature of the implant prosthesis, which is subject
to the planning and design of the clinician, while the peri-implant soft tissue margin is the
respective feature of the peri-implant mucosa, formed in response to the CM. Around natural
teeth, the Cervical Margin will coincide with the most coronal part of the periodontal sulcus.
In implant supported prosthesis, the CM is a prosthetic concept which is defined by the visible
portion of the implant crown (Figure 2). Again, the Cervical Margin ideally coincides with the
most coronal part of the peri-implant sulcus.
iii) Implant-abutment junction
The interface between the implant and the abutment is probably the most studied and best
documented junction, which has evolved significantly as a result. The original configuration
of an external hex, flat-to-flat connection of the Brånemark implants, has been followed by a
wide arrange of designs, most notable changes being the internal, tapered connections and the
concept of platform switching. The original flat-to-flat external connection was reported to
allow wider micromovement (30) and also potential microleakage (31). The fact that in this
configuration the implant-abutment junction was placed at the bone level, might have been the
reason for the marginal bone resorption or remodeling observed during the first months post-
surgery, which might have led to the wide acceptance of 1.5mm marginal bone loss during the
first year post surgery as a biologic consequence of bone remodeling (32). Bacterial and fluid
microleakage has been related to oral malodour, inflammation and marginal bone loss, apart
from the potential technical implications it could have for the long-term tight fit of the
connection (33,34). On the other hand, implants with an internal tapered connection and
platform switching have been shown to increase connection fit and stability (30, 35),
effectively prevent microleakage (36), while interface gaps are found to be no more than 1-2
μm (Figure 3) (37). Albeit implants with such configurations have demonstrated clinically less
marginal bone remodeling during the first and also consecutive years post-surgery (38, 39),
microbiological investigations have shown bacterial contamination of the implant abutment
junction in both external and internal connection types after 5 years in function (40). Seen
collectively, such results suggest that although the connection design might influence bacterial
activity levels qualitatively and quantitatively, no design has been shown to be clinically
completely immune to effects of microleakage in the long term. At the same time, it should be
noted that not all implant configurations might achieve very tight fit of the implant-abutment
junction, in particular when third party prosthetic components are used (Figure 4)
Tissue level implants are not designed to have an implant-abutment junction at the bone level,
but more coronally in the ISC, depending on the height of the implant soft tissue collar. In the
time of flat-to-flat external hex connections, the absence of an implant-abutment junction on
Tissue level implants was considered by many a “safer” configuration, as it eliminated the risks
associated with the junction being close to the marginal bone. Nevertheless, the height of the
soft tissue collar is an important parameter, seen under the light of the current understanding
of essential vertical dimensions of soft tissue. A soft tissue collar of less than 2mm might be
too short to properly accommodate the adequate soft tissue vertical dimensions. Furthermore,
the implant-abutment junction on tissue level implants is less precise, even if tight. As the
abutment sits externally on the implant collar, minor vertical discrepancies are shown to result
in a significant “undercut” of 50-100 μm (Figure 5) (41), which if populated with biofilm might
turn into a plaque retentive point. As this junction almost always is located in the apical section
of the sulcus, continuous apical migration of the biofilm reaching this point could exacerbate
the vicious circle of peri-implant tissue inflammation. This might reduce our ability to disinfect
the implant after being affected by Mucositis, if this junction is placed deep in the ISC (5).
iv) Abutment-prosthesis junction
The abutment-prosthesis junction (APJ) can be present in both bone and tissue level implants
but varies significantly between implant systems and types of restoration. In certain “one piece”
APJ configurations (e.g. precious alloy abutments where the prosthesis is being cast on the
abutment) this junction might not be detectable clinically, as the abutment and the prosthesis
are fused. When present, the abutment-prosthesis junction is intended to be within the sulcus
and thus it is of high clinical significance.
The interface between the implant and the prothesis is commonly structured in four different
ways (Figures 6-7 / a,b,c,d):
a. Prosthesis cemented on an extra-orally cementable, screw-retained abutment, such as a
In this configuration, the often milled or CAD/CAM prothesis will be cemented outside the
mouth. The prosthesis-abutment complex is then polished and placed in the mouth as a one-
piece, screw retained restoration (42)
The extraoral cementation eliminates the risk of cement rests, yet a thin layer of cement is very
likely to be exposed in the abutment-prosthesis junction, even at ideal conditions (Figure 8)
(43). Even when tight, the interface between abutment and prosthesis in such cases can result
in some discrepancies that can act as plaque retention points. A alternative configuration is
prosthesis cast on top of a base abutment, which will result in a one-piece restoration without
any clinically detectable interface between abutment and prosthesis.
b. Prosthesis cemented on an intraorally cementable, screw-retained abutment
In this configuration, the prothesis will be cemented in the mouth typically due to aesthetic
requirements when the implant angle is not optimal. In such cases the abutment-prosthesis
junction coincides with the cementation level, so it is important to place it as close to the sulcus
opening as possible. The risk of cement rests increases significantly when this junction is
placed deeper in the sulcus (44). Cement rests can constitute a major long term risk either being
pushed under the junctional epithelium jeopardizing the integrity of the ITC and/or through
acting as plaque retention points (45).
c. Prosthesis retained by a screw on an intermediate abutment.
This configuration will result in a reconstruction with one or two screws for every
implant. Tight fit of both the implant-abutment and abutment-prosthesis junctions is
paramamount to prevent microleakage and plaque retention.
d. Prosthesis directly to the implant (without an intermediate abutment).
A typical example would be a milled bridge on implant level. This will result in one screw
retaining the prosthesis on each implant. Studies have shown prostheses of that type on bone
level implants to present with increased risk of bone resorption (46), possibly related to
increased risk of misfit. The tight fit of this junction as well as the absence of misfit,
discrepancies and gaps is of paramount importance, otherwise bacterial products through
microleakage and / or plaque retention will directly affect the sulcus. In-vitro studies have also
documented that even small misfit in bridges with this configuration can have detrimental
effects to the veneering as well (46). Certain laboratory manufacturing processes resulting in
an oxidation layer on surface of the prosthesis might affect the tight fit, as the oxidation layer
has to be often removed with sandblasting, thus altering the prosthesis surface which connects
with the implant (41) .
3) Bacteria – Oral Biofilm
Plaque accumulation is detrimental for the health of peri-implant tissues. Studies of
experimental peri-implant mucositis in humans have shown that undisturbed plaque
accumulation will lead to inflammation of the peri-implant tissues within three weeks without
any exceptions (5, 48-50). At this point it is important to emphasize that detrimental peri-
implant inflammation is not caused by the presence of bacteria in the sulcus in planktonic status,
but rather the result of accumulation of mature pathogenic biofilm. Biofilm formation requires
a solid hard surface and a liquid environment infected with bacteria. As both conditions are
met on the surface of the prosthesis, Biofilm forms first on the part of the prosthesis exposed
in the oral cavity and it first interacts with the soft tissues at the Cervical Margin. Establishment
of a mature, pathogenic biofilm at the Cervical Margin will require at least 7-14 days, after
which it will provoke the immune response and lead to inflammation of the oral mucosa (5,48-
50). In the case of oral mucosa not in proximity to implants, the inflammation remains limited
superficially in the mucosa, as for example under an uncleanable prosthesis pontic or a denture.
However, biofilm accumulation in close proximity with the peri-implant sulcus leads to
inflammatory response from the peri implant soft tissue margins and the sulcular epithelium,
leading to peri-implant mucositis, kickstarting a vicious circle eventually resulting to apical
migration of the junctional epithelium, peri-implantitis and formation of peri-implant pocket.
There is at present no evidence that the depth of sulcus will influence the initiation of peri-
implant mucositis. On the contrary, a study of experimental mucositis (5) showed that peri-
implant tissues around shallow and deep sulci remained equally healthy with the application of
professional maintenance care and patient performed oral hygiene, thus maintaining the
cervical margin free of biofilm. The same study however, suggested a less favorable pattern
of resolution when peri-implant mucositis was initiated in tissue level implants with a deeper
B. Clinical implications for the design of the Implant Supra-crestal Complex
i) ISC and plaque induced peri-implant inflammation
Recent evidence has demonstrated that peri-implant tissue in particular mounts a greater host-
inflammatory response to plaque accumulation than those at teeth (51), suggesting that plaque
control around implants may be of critical importance in averting the cascade of destructive
inflammatory peri-implant disease. There are two main factors that can expose the peri-implant
sulcus to the detriments of biofilm accumulation: deficient oral hygiene and improper design
of the Cervical Margin. The former one requires the proper training and motivation of the
patient, while the latter is an iatrogenic condition. When the Cervical Margin coincides with
the coronal margin of the peri-implant sulcus, oral hygiene can efficiently remove the biofilm
from the proximity of the sulcus (Figure 2). On the contrary, a non-anatomical Cervical Margin,
as this is created by the commonly used, cylindrical in shape, stock abutments, can be located
away from the sulcus resulting in a horizontal discrepancy between cervical margin and sulcus
or “Ridge Lap”. Plaque accumulation in proximity of the sulcus can then proceed with little
or no inhibition from oral hygiene, posing a significant risk and increasing the prevalence of
peri-implantitis (52). The wider the prosthesis the bigger this Ridge Lap becomes; in particular
as we move from the anterior to the posterior site restorations, since the lateral size of the
prosthesis increases. An improper Cervical Margin could furthermore inhibit monitoring of the
health of peri-implant tissues, preventing efficient probing or resulting in false negative
probing depth, thus underestimating the extent of bone loss (53). As the design of the Cervical
Margin is a key for access to oral hygiene and sustainability, calculation of the Emergence
Angle in implant prosthesis for exactly this location might be a much more clinically relevant
measurement, as it was conducted on natural teeth. A tangent line to the Cervical Margin of
the implant prosthesis might reflect the ability to maintain oral hygiene much more precisely
than a line drawn for the whole Emergence Profile. A wide Emergence Angle there would
approximate a ridge lap and inhibit Oral Hygiene, while a narrow one will resemble the
emergence angles reported for natural teeth (27,28). To do such a calculation on implants
however, we will require a precise location of the mucosal margin, which cannot be done
Avoiding the need for a ridge lap design necessitates the placement of the implant in the
optimal restorative position, angle and depth (Figure 9). Katafuchi et al showed a correlation
between the depth of placement of bone level implants and the emergence angle, with the latter
being more favorable when implants were placed subcrestally (29). This indicates that
although subcrestal placement of bone level implants should not be seen as a norm, it might be
essential if directed by the need to create the desired prosthesis contour, cervical margin and
ii) ISC and implant -abutment / prosthesis junctions
Attention needs to be paid to the risks presented by any “gaps” within the supra-crestal complex,
as the ones that might be created in the implant-abutment or implant-prosthesis junctions. Such
interfaces -if not tight enough- might facilitate microleakage and circulation of bacterial
products into the ISC, while micromobility of the components might also contribute to
problems. Furthermore, gaps within the ISC might act as retention points when infected with
biofilm, possibly inhibiting disinfection efforts through professional means and oral hygiene
and complicating the resolution of inflammation. Modern bone level implant systems with
internal connection, can achieve a very tight fit in the implant-abutment junction, which can be
at the level of 1-2 μm. In addition, in the case of bone level implants with platform switch, the
implant-abutment junction remains well apical of the junctional epithelium, thus potentially
protected by direct plaque contamination in the early stages of mucositis. Nevertheless, screw
loosening of the healing, temporary or prosthetic abutment at the bone level implant could
potentially be more detrimental to the bone margins and the tissue health than in the case of a
The implant-abutment junction of tissue level implants presents with a different configuration,
still however the fit of the components can be equally tight in the range of 1-2 μm (Figure 5).
Depending on the height of the smooth collar, this junction is in most cases exposed in the
sulcus coronal of the junctional epithelium, or close to the sulcus opening, thus more easily
accessible through oral hygiene. Abutment loosening in this case might be less detrimental than
in the case of bone level. Nevertheless, if this interface is deep in the sulcus as in the case of
increased vertical dimension of the soft tissues or in subcrestal placement, this area could act
as a difiicult to disinfect retention point, if colonized with biofilm. It is therefore advisable to
avoid the placement of tissue level implants at sites with increased vertical soft tissue height,
which would result in placing the implant-abutment junction several millimetres under the
Cervical Margin. Subcrestal implant placement is well documented in the case of platform
switching Bone level implants, but should be avoided with Tissue level implants, as it would
result in the placement of the less precise implant-abutment-prosthesis junction (Figure 5) deep
under the supracrestal complex tissues.
The authors accept that the use of these terms and the definition of the respective anatomical
and morphological structures correspond to a configuration during ideal conditions. For
example, in the case of subcrestal placement of a bone level implant, the Supra-crestal complex
will be established from below the implant crest, thus seemingly contradicting the term. The
term “Supra-platform implant Complex” was thus proposed to address such a configuration,
the authors however acknowledged that such a term will be confusing in the case of Tissue
Level implants, where the “platform” is already some millimeters coronal of the bone crest in
the Complex. Consequently, the authors have decided to describe the anatomic and
morphological landmarks of importance which will be present in most common Implant-
Abutment-Prostheses configurations, while acknowledging that some very specific implant
systems or configurations might not fall exactly within this terms. The terms have been thus
described for bone and tissue level two-piece implants which are being placed for axial loading.
Even within this category of implants, significant diversity of the design persists, for example
in the height and angle of the transmucosal collar of tissue level implants, or the presence and
extent of platform switching in bone level implants. The authors also acknowledge that there
exist a significant diversity of implant systems, connections and combinations, with potentially
different level of precision and fit of components. The samples that have been used for
discussion in this paper originate from specific published research in peer-reviewed journals
and is only addressing the conditions and results of these investigations. The use of different
material for the sub-mucosal components, such as titanium, gold alloys, ceramics and also the
use of non-original prosthetic components and screws might also impact the tissues and
configuration of the Supra-crestal complex.
Furthermore, the authors believe that as with any anatomic feature, the dimensions and
structure of the peri-implant tissue can present with significant, physiological variation
between individuals or different anatomic sites in the same person (20). Histological studies in
humans are scarce and typically based on very few samples. Even so, the means describing the
dimensions are accompanied by high standard deviations, suggestive of significant variation.
The authors would like to thank Professor Lisa Heitz-Mayfield for her critical review and
important feedback to the writing of this paper.
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Figure 1. Natural scalloping of the periodontal tissues corresponding to the interdental
papilla is a result of the corresponding bone anatomy and root morphology of the natural
teeth. Simulating this interproximal scalloping with implants, in particular in the aesthetic
zone is only possible through a deep peri-implant sulcus at the interproximal sites. The
Emergene Profile remains the transition from the bone crest to the cervical margin, regardless
if Bone or Tissue level implants are utilised. Interproximal view of the Connective Tissue
(CT) and Junctional Epithelium (JE) space, Emergence Profile (yellow line), the Cervical
Margin (red line) and interproximal sulcus depth (probe) for bone (left) and tissue level
(right) configurations of the Supracrestal Complex.
Figure 2. Tissues of the Emergence Profile in a typical Implant-Abutment-Prosthesis
complex in the aesthetic zone. Subcrestal placement of this bone level implant (in relation to
mesial and distal bone level on neighbouring teeth) has allowed for maintaining the desired
scalloping of the soft tissues, but resulted in increase of sulcus depth in the mesial and distal
area. Observe that implant position and the design of the Emergence Profile allows for the
Cervical Margin to coincide with the most coronal part of the sulcus, as in natural teeth.
Figure 3. Implant abutment junction under the Scanning Electron Microscope of Bone level
implants. a,b Astratech Morse Taper internal connection at 32x(a) and 120x(b). c,d Strauman
Bone Level Crossfit connection at 20x(c) and 55x(d) magnification. The tight fit at the
implant shoulder in both cases allows for a gap of less than 2 μm.
Figure 4: Straumann bone level implant restored with a,b) Straumann Cares abutment and
c,d) third party abutment at 20x(a, c), 40x(b) and 27x(c) magnification. Deficient fit of the
abutment in the coronal part of the internal connection is evident in c,d.
Figure 5. Implant abutment junction under the Scanning Electron Microscope of Tissue level
implants. a,b Strauman Tissue Level Synocta connection with Gold abutment at 30x (a) and
100x(b) magnification. c,d Strauman Tissue Level Synocta connection with third party
Titanium abutment at 13x (c) and 100x (d) magnification. Observe the tight fit between the
implant and abutment at the shoulder which in both cases allows for a gap of less than 2 μm,
but also the horizontal discrepancy which in both cases creates an “undercut” exceeding 50
Figure 6. Common current types of implant-abutment-prosthesis configurations. Schematic
representation on Bone Level implants. a) Prosthesis cemented on an extra-orally cementable
abutment such as a Ti-base. b) Prosthesis cemented on an intraorally cementable abutment c)
Prosthesis retained by a screw on an intermediate abutment. d) Prosthesis directly to the
implant (without an intermediate abutment).
Figure 6a,b,c,d. Details of IAP interface of a) prosthesis cemented extra-orally on abutment,
b) Prosthesis cemented on an intraorally cementable abutment c) Prosthesis retained by a
screw on an intermediate abutment. d) Prosthesis directly to the implant (without an
intermediate abutment) for Bone Level implants. Red line: Peri-implant soft tissues and
emergence profile. Red line: Peri-implant soft tissues and emergence profile. Blue line:
Prosthesis-abutment junction. Yellow line: Implant-Abutment junction.
Figure 7. Common current types of implant-abutment-prosthesis configurations. Schematic
representation on Tissue Level implants. a) Prosthesis cemented on an extra-orally
cementable abutment such as a Ti-base. b) Prosthesis cemented on an intraorally cementable
abutment c) Prosthesis retained by a screw on an intermediate abutment. d) One piece
prosthesis cast on abutment.
Figure 7a,b,c,d. Details of IAP interface of a) prosthesis cemented extra-orally on abutment,
b) Prosthesis cemented on an intraorally cementable abutment c) Prosthesis retained by a
screw on an intermediate abutment. d) Prosthesis cast on the abutment for Tissue Level
implants. Red line: Peri-implant soft tissues and emergence profile. Red line: Peri-implant
soft tissues and emergence profile. Blue line: Prosthesis-abutment junction. Yellow line:
Figure 8. Slice of Prosthesis after extraoral cementation on a titanium abutment and polish. A
thin layer of cement is present in the interface between the prosthesis and the abutment, while
the undercut between implant and abutment is also visible. Magnification 40x at the Scanning
(Figure 9). Placement of this Bone Level implant in a shallow and palatal position has
resulted in the need of a ridge lap in order to fulfil the aesthetic requirements of the
prosthesis. a) vertical height between implant shoulder and most apical part of the peri-
implant mucosa margin is only 1.5 mm b) Ridge lap of the cervical margin of the prosthesis,
inhibiting the access of plaque control to the opening of the sulcus buccally.
Red line on the crown indicates the Cervical Margin.