The long-term functional success of implant treatment depends on the stability of the crestal bone around the implant platform. The esthetic result is achieved by adequate quality and quantity of soft tissue in the peri-implant area. The soft tissue creates the buffer area that ensures the mechanical and biological protection of the underlying bone. Therefore, it is necessary to maintain in the long term, not only implant osseointegration, but also the integrity of the soft tissue around the sub- and suprastructures of the implant restoration. To create the protective soft tissue area, it is necessary to ensure 3 criteria. This treatment approach will be defined as TWS–soft tissue management: T for thickness, W for width, and S for stability. There are many ways to achieve the first 2 criteria, which are described in the literature. Achieving the third criterion of stability has become possible only recently because of the development of digital treatment planning, surgically guided, and prosthetic-assisted technology that uses a 1-time abutment and its implementation into the dental practice. The purpose of this article is to present with clinical cases a detailed description of each criterion.

Dental implantology is one of the most widespread methods of rehabilitation for patients with single, multiple, or full-arch loss of teeth. The foundations of modern dental implantology were laid by Branemark.1  This applied method of treatment should be successful not only in the short term but also in the long-term perspective. The definitions of success criteria in implantology were published by several authors starting in the late 1970s.26  This criterion assumes the absence of the following: (i) implant mobility, (ii) radiolucency of peri-implant tissues, (iii) pronounced resorption of the bone in the proximal area of the implant platform, and (iv) infection and patient discomfort. In addition to the above-mentioned factors, the esthetic rehabilitation and satisfaction became a new criteria consideration for the anterior edentulous space. However, restorative therapy whether a composite, an inlay/onlay restoration, a single or multiple individual implant restoration(s), or a multi-unit fixed bridge is intimately tied to periodontal principles and requirements. Any attempt at restorative therapy in the absence of periodontal health is doomed to eventual failure. Therefore, daily oral hygiene by the patient and regular professional maintenance are prerequisites for long-term stability of periodontal health around any implant restoration.

Successful implant treatment depends not only on the periodontal health of the patient but also on genetic and immunologic factors such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β levels. The latter have been defined as the genomic and innate markers that determine treatment success.7  It should be mentioned that uncompensated parafunctions, unhealthy lifestyle, uncontrolled diabetes, lack of vitamin D, depressed immune function, obesity, periodontal disease, smoking, and unsatisfactory oral hygiene can negatively influence the treatment results and success.

Long-term periodontal, functional, and esthetic success in implantology, especially in the anterior zone, is achieved by and dependent on 4 factors8:

  1. Periodontal health and daily oral hygiene by the patient and regular professional care and monitoring

  2. Bone stability proximal to the implant and particularly adjacent to the implant connection

  3. Quantity/quality of the peri-implant soft tissue to create a proper emergence soft tissue profile initially with the temporary restoration(s) that considers the pink esthetic score (PES)

  4. A perfect permanent (definitive) implant supported restoration, duplicating the previous temporary crown that also respects PES parameters

Additionally, the soft tissue creates the buffer area that ensures the mechanical and biological protection of the underlaying bone. Thus, it is necessary to not only achieve osseointegration of the implant but also mucogingival integration of the soft tissue adjacent to the implant's sub- and suprastructure.

The protective function of the soft tissue is necessary because of the oral cavity's aggressive environment regarding pathogenic microorganisms. The underlying bone must be protected from the invasion and presence of pathogenic microorganisms. There is 1 function of great importance and that is the soft tissues should maintain a long-term hermetic seal to the implant and its restoration. The seal mechanism will be formed progressively around teeth and implants. This seal forms following a tooth's eruption or the placement of the implant's restoration. A faulty mucosal tissue seal around teeth or implant(s) permits aggressive microflora access to the underlying bone. When such conditions exist, there should be the formation of a protective mechanism to separate the outside world from the inside of the body. In 1961, Gargiulo et al9  named this seal the dento-gingival junction, and in 1977, Ingber et al10  named it the “biological width.” It can be considered the protective soft tissue biologic buffer area. The soft tissue biological buffer area is formed around the implant and its sub- and superstructure.

This biological width should be considered among the similar characteristics found between the soft tissue components around teeth and implant(s); however, there are some soft tissue differences such as size and placement of collagen fibers.11 

The protective biological width in the peri-implant zone consists of the epithelial attachment and connective tissue attachment. The gingival sulcus does not belong to the biological seal. The epithelial hemidesmosomes attachment ensures a biological protective function. Microorganisms at the epithelial attachment stimulate an immune response from the host and are eliminated by the immune cells (immunocytes). This area exhibits a small degree of inflammation even in normal noninflammatory conditions. Additionally, the connective tissue attachment performs its mechanical protective function by protecting the underlying bone from mechanical mastication trauma during the chewing process. Normally, this area is never contaminated.

To form the protective soft tissue buffer area, it is necessary to apply a special treatment protocol that ensures 3 criteria. The authors refer to this treatment protocol as soft tissue management WHS: W, width; H, height; S, stability.

Width

Berglundh and Lindhe12  performed a study in dogs that found to form the protective soft tissue buffer area, a certain amount of the soft tissue thickness is necessary. If the thickness is not enough, there will be resorption of the cervical implant bone.

In 2009, Linkevicius et al13  determined the effect of the gingival thickness on the degree of bone resorption around implant connections. This study found that the thickness of the gingiva had a significant effect on the stability of the marginal bone around implants. One year after implant placement, when the gingival thickness was 2 mm or less, bone loss adjacent to the implant platform may reach 1.45 mm.

Therefore, to ensure the prevention of the cervical bone resorption, it is necessary to have a crestal gingival thickness of ≥3 mm above the implant connection.

First Clinical Case (Figures 1 Through 9)

A 43-year-old male patient in good health and without any confounding habits presented at the clinic to replace his missing mandibular right molar. The patient noted that 7 years earlier an implant was placed in the position of the missing tooth #30, but 5 months later, the implant had to be extracted because of an osseointegration failure.

When treatment planning for the new implant, a radiographic analysis was performed, and the gingival width was 2.5 mm (Figure 1); thus, the crestal presurgical gingival thickness was not enough to form an adequate soft tissue buffer area. During the procedure, once the implant was placed, an augmentation of the soft tissue was provided by a connective tissue graft that was harvested from the palate using a single-incision technique14  (Figures 2 and 3). The achieved radiographically evaluated crestal soft-tissue thickness was 6 mm (Figure 4).

The height of the soft tissue after placement of the healing abutment had a width of 4 mm and height of 6 mm (Figure 5). A screw-retained temporary zirconium dioxide crown was placed. The gingival height around the temporary restoration measured at 1 year after placement was also 6 mm. The radiograph demonstrated the absence of implant cervical bone resorption (Figure 6). The absence of the resorption is explained by there being enough soft tissue width and height present to form the protective soft tissue buffer area. The permanent crown was made of multilayer zirconium dioxide and screw retained to the implant (Figure 7). The clinical and radiographic images of the permanent crown 1 year after placement demonstrates no implant cervical bone loss (Figure 8).

In this present clinical case, the soft tissue width and the height of the attached gingiva were initially at a minimum. The case was performed based on the present authors original 2013 published methodology.15  The purpose of this method was to increase the width and height of the soft tissue adjacent to the platform area at the time of implant placement. A detailed video was recorded based on this clinical case. It can be viewed at the provided link (Figure 9).

Height

Adibrad et al16  provided a study evaluating 66 functioning implants with the goal of defining the relationship between the width of the keratinized gingiva and the condition of the tissues adjacent to the implant and its prosthesis. Findings demonstrated that when the width of the attached gum is less than 2 mm, the complications of the implant treatment were more significant than in cases with wider zones of the attached gingiva. Lin et al17  provided a literature review, from 1965 to 2012, that related the important role of keratinized gingiva in the success of the implant treatment. The authors concluded that a small amount of keratinized gingiva (<3 mm) had a negative impact on the success of the implant treatment. Therefore, to prevent the recession of the peri-implant soft tissue and bone resorption, it is necessary to create an area of the keratinized gingiva of no less than 3–4 mm in width.

Second Clinical Case (Figures 10 Through 15)

A 43-year-old female patient, in good health and without confounding habits, came into the clinic with complaints of moderate pain arising from pressure on the mandibular right first molar (tooth #30). From the patient's anamnesis: 10 years earlier, tooth #30 was endodontically treated, and then 4 years ago, it was re-treated; the remaining tooth structure was restored using a fiberglass post and subsequently a cement retained crown. A week before this consultation, while eating, she experienced severe pain at tooth #30; subsequently, this pain increased with an associated pressure. The diagnostic examination revealed a tooth fracture at the tooth's bifurcation.

Tooth #30 was extracted, an implant was placed, and the healing abutment was installed. At 3 months, before the start of the prosthetic phase of treatment, a depression of the soft tissue was observed on the buccal side of the implant. The ridge was modified by the normal biological healing process of the socket with its usual biological decrease in the vertical and horizontal dimension.18  The ridge was also affected by the chronic mechanical trauma to the soft tissue because of the absence of an optimal band of keratinized gingiva on the buccal side (Figure 10). It was decided a few weeks after the implant uncovering to graft the buccal ridge site with a free epithelial connective tissue graft (FECTG). The procedure was performed to create an optimal band of attached keratinized gingiva (Figure 11). This method is known for predictable outcomes provided surgical prerequisites are followed.

The method became widespread in 1968 after Sullivan and Atkins,19  Gordon et al,20  and Sullivan and Atkins21  published a 3-article series describing in detail the principles of the applied method. It should be mentioned that apart from some modifications, the information presented in those articles remains relevant today.

Two months following graft surgery, full regeneration of the donor-site soft tissue was demonstrated. At the recipient site area, a sufficient width and height of attached keratinized gingiva was formed to prevent damage from the trauma of chewing to the peri-implant soft tissue (Figure 12). The permanent implant restoration was an abutment of a titanium base combined with added zirconium dioxide and a crown made of the multilayer zirconium dioxide fixed to said abutment using a permanent cement (Figure 13).

During a regular postrestorative examination, an acceptable clinical state was observed. The obtained width and height of the attached gingiva were more than 5 mm with no observed mechanical trauma or irritation (Figure 14). Thus, the formed soft tissue protective buffer area fully performs its intended biological and mechanical protective functions for the underlying bone. The radiographic examination demonstrated the absence of bone resorption adjacent to the implant platform (Figure 15).

Stability

In 1997, Abrahamson et al22  provided morphology for a dog study. Results revealed that the more frequently prosthetic suprastructures were disconnected from the implant bodies, the more significant was implant related crestal bone loss. In 2018, a literature review was conducted to determine the degree abutment disconnections and reconnections affect bone resorption and soft tissue healing in the peri-implant area. After a detailed analysis of 14 articles (535 patients with 994 implants), the authors determined that repeated abutment disconnections and reconnections of prosthetic superstructures: (1) negatively affected the stability of peri-implant tissues, (2) increased the degree of peri-implant bone resorption, and (3) promoted the formation of buccal soft tissue recessions.23 

Therefore, to prevent these phenomena, it is beneficial to avoid the disconnection of the abutment(s) and restoration(s) (temporary or permanent) from the implant connections at all stages of the treatment. At the time of surgery, a 1-time abutment should be placed and never unscrewed or removed.

Third Clinical Case (Figures 16 Through 32)

A 57-year-old female patient in good health without confounding habits presented to the clinic complaining about the progressive loosening of the crowns on the maxillary right and left central incisors (teeth #8 and #9; Figure 16). The patient reported that a few years ago, she had ceramic-metal crowns placed on these teeth; the tooth structures of both teeth were restored with metallic cores. Clinical and radiographic examinations revealed a longitudinal fracture of tooth #9 and a mid-root perforation of tooth #8. During the surgical procedure, the crack in the root of tooth #9 (Figure 17) and perforation at the mid-third of the root of tooth #9 (Figure 18) were visualized.

Treatment indications for teeth #8 and #9 were extractions The treatment plan included the following: (1) simultaneous teeth extractions, (2) immediate implant placements using a digitally designed surgical guide, (3) placement of prefabricated individual abutment to each implant, and (4) fixation of prefabricated temporary crowns to the abutments at the subgingival level.

A virtual model was created before the surgery to (1) show the bone level, (2) show the soft tissue contours, (3) aid in providing the ideal 3-dimensional (3D) positioning of implants (Figure 19), and (4) to create the surgical guide that will then be fabricated using a 3D printer. A digital impression was taken from the virtually installed implants and sent to the dental laboratory. The permanent individual abutments and temporary crowns were made using Computer-Aided Design/Computer-Aided Manufacturing technology. During the surgery, teeth #8 and #9 were extracted using a minimally invasive approach. Then debridement of the alveolar sockets was performed (Figure 20).

The surgical guide was fixed to the teeth. The accuracy of guide placement on the teeth was checked using the existing control teeth openings (Figure 21). Implants were placed through the same guide using 2 implant drivers. The first driver ensured the preliminary positioning of the implants in 3D space, and the second driver placed the implants in the desired 3D position at the optimal depth. Their antirotation elements were fixed in a strict position by combining special location elements of the surgical guide with the implant drivers (Figures 22 and 23).

The laboratory fabricated permanent 1-time individual abutments, and temporary crowns were fixed to the implants with screws torqued to 35 Ncm (Figure 24). It is necessary to note that during all prosthetic stages and to exclude any trauma to the new emergence soft tissue profile, the unscrewing of these abutments was not planned (Figures 25 and 26). Temporary crowns were fixed to the abutments with permanent cement. The temporary crowns were splinted to each other and therefore served as accuracy markers of the presented method. If there was any inaccuracy in 3D positioning (depth and/or orientation of antirotation element) of the implants, the splinted temporary crowns would not fit the abutments properly (Figures 27 and 28). Before the placement of the permanent prothesis, a Cone Beam Computed Tomography image of the bone was taken (Figure 29). The permanent crowns were provided at the abutment level and constructed from multilayer zirconium dioxide. These crowns were fixed to the 1-time abutments with permanent cement (Figures 30 and 31).

The digital 1-time dental implant installation navigation implantation method used in this treatment was developed in 2016 and patented in 2018. The protocol is a digital protocol for navigation implantation and is named DDS (Digital Date Save).24  The technology digitally creates the ideal soft tissue emergence profile around the permanent individual abutments that ensures the stability of the bone level in the region adjacent to the dental implant platform.25,26  A surgical video of the DDS procedure can be found at the link provided in Figure 32.

Osseointegration is no longer the sole long-term principal objective of implant therapy. The contour and quality of the soft tissues plus the prosthesis emergence profile, shape, and shade must mirror the adjacent teeth as closely as possible.27 

To achieve the successful result of any implant treatment from a long-term functional and esthetic aspect, it is necessary to ensure the stability of the hard and soft tissues adjacent to the implant and its superstructure. Soft tissue grafting techniques are commonly used to improve esthetics on the buccal (labial) surface of the implant(s). The modified roll flap has the benefit of an enhanced blood supply that can ultimately result in faster healing because of it being a vascularized pedicle donor with superior gingival color.27 The bone level adjacent to the implant platform connection is 1 of the key indicators of treatment success.6  It is accepted that design features of implants can affect the degree of bone loss. Additionally, there is a micro-gap (interface) that occurs at the connection of the abutment to the implant.

The effect of the micro-gap for 1-component and 2-component implants related to the (1) initiation of inflammation in peri-implant soft tissues and (2) degree of bone resorption were studied in detail in comparative animal studies.28  Two-component implants with different micro-gap (interface) dimensions between the implant body and abutment that were either welded together or retained by a trans-occlusal screw were evaluated.29  Data revealed that the size of the micro-gap is 1 of the main factors for bone loss adjacent to the implant platform. The level of the crestal bone is also influenced by the presence of a polished neck surface on the implant and the level of its insertion into the bone.30,31 

In 1995, Ericsson et al32  published the results of a study suggesting that the crestal bone in the postoperative period underwent remodeling because of (1) surgical bone stress and (2) existing localized inflammation in the connection area between the implant and abutment. Formation of infiltrate is the protective response to the pathogens colonizing in the micro-gap. Lazzara and Porter33  published an article that described the concept of platform switching based on the “shift” of the implant/abutment connection area in the centripetal direction relative to the axis of the implant. This “shift” is caused by the use of a narrower diameter abutment connection than the implant platform. Thus, the area of localized inflammation shifts away from the bone crest while circumstances to diminish the level of bone resorption relative to the implant platform are created. Subsequent studies confirmed the effectiveness of using the displaced platform (aka platform switching or “shift”) concept to prevent bone resorption.3436 

Linkevicius et al37  published the results of a study that examined if thin mucosal tissues affect crestal bone stability adjacent to implants using platform switching. According to the “zero bone loss” hypothesis, implants with platform switching would be associated with less crestal bone loss compared with implants with traditional interface. There were 2 main criteria for a patient's inclusion: (1) thin mucosal tissues (≤2 mm) that covers the edentulous alveolar ridge and (2) an edentulous gap large enough for at least 2 implants in any region of the mouth, with a minimum of 3 mm between implants and a minimum of 1 mm between implant(s) and adjacent tooth/teeth. The results of this pilot study demonstrated that platform switching modification does not prevent crestal bone loss if mucosal tissues are ≤2 mm thickness at the crest of the edentulous ridge before implant placement. Test and control implants had very similar amounts of marginal bone resorption; the differences were not statistically significant.37  Therefore, platform switching alone is not enough to prevent crestal bone loss. Based on the results of the above experimental and clinical cases,12,13,37  it may be concluded that the formation of a protective soft tissue requires a minimal thickness of soft tissue above the implant platform.

In 2015, Linkevicius et al38,39  evaluated the effect of soft tissue thickness on crestal bone height for implants with different connections. It should be noted that when tissue thickness was 3.32 mm around regular implant connections and 2.98 mm in thickness around platform-switched implants, no bone loss was observed, which indicates that the ideal proximal implant tissue thickness should be considered ≥3 mm.

In 2017, Canullo et al40  correlated soft tissue thickness and peri-implant bone remodeling adjacent to the platform-switching implant abutment. Based on the authors' results, it was concluded that the initial mucosa thickness surrounding a bone-level platform-switching implant did not influence the pattern of physiologic marginal bone loss. However, Linkevicius41 stated that soft tissue thickness of 3 mm or more is required for bone preservation with a platform-switch of greater than 0.8 mm.

In 2005, a clinical study examined the effect of the surface topography of single-component experimental mini-implants on the formation of the peri-implant soft tissue barrier (PISB).42  The authors concluded that dependent on the surface treatment of the implants, there are differences in the sizes of the epithelial and connective tissue attachments. The results further demonstrated that regardless of the type of the surface treatment of the implant, the minimal soft tissue thickness required for the formation of a peri-implant soft tissue barrier was 4–4.5 mm.

In 2010, Wiesner et al43  concluded that connective tissue grafts performed at the time of implant placement are effective in increasing soft tissue thickness and thus also improving esthetics. This study further demonstrated that, regardless of whether soft tissue augmentation was performed at the time of implant placement (test group) or not (control group), after a year in all cases, 1 mm of bone resorption was observed adjacent to dental implant connections. This can lead to the conclusion that an increase in the thickness of the peri-implant soft tissue is not enough to prevent immediate bone resorption. It is necessary to apply an integrated approach when working with soft tissues aimed not only at increasing the thickness of the crestal soft tissue, but also at creating an adequate vertical height of the buccal (labial) attached gingiva.

The criteria for successful implant treatment are to create a protective soft tissue area that prevents trauma to the underlying bone over time. It should be noted that to create a protective soft tissue emergence profile in the coronal direction that will eliminate, or significantly reduce, bone resorption in the area of the implant platform, it is necessary to achieve a soft tissue thickness of 3 mm and more.12,13  The width of the keratinized gingiva in peri-implant areas should be approximately 3–4 mm.16,17  Today, there are many surgical methods for increasing the thickness of the soft tissue and creating the necessary zone of the keratinized gingiva.

Because of the development of new products and digital technologies, there is an opportunity to attach a prefabricated permanent individual abutment(s) to the implant(s) on the day of the surgery and not disconnect them for future prosthetic stages. The use of 1-time abutments will (1) avoid trauma to the formed emergence soft tissue profile buffer area created with any type of soft tissue graft and (2) preserve the cervical contour obtained with the temporary crown.

To achieve a successful implant result by today's standards, it is necessary to respect the objectives of both optimal functional and esthetic outcomes. Esthetics will be evaluated using the pink esthetic score (PES) and white esthetic score (WES).44  Therefore, modern implantology must start with a motivated oral hygiene patient, with no periodontal disease; have optimal preimplant bone volume for perfect 3D implant(s) position/orientation; and perform correct management of soft tissues by applying known clinical and biological concepts of periodontal and mucogingival surgery.

Soft tissue management must be considered when performing (1) preoperative evaluations, (2) first- or second-stage implant surgical procedures, and (3) during prosthetic treatments. These considerations are necessary to achieve long-term, predictable, and stable results from the periodontal, functional, and esthetic perspectives.

When possible, clinical results that can be achieved with the (1) least number of surgical interventions, (2) lowest risk of complications or morbidity during healing, (3) least amount/severity of pain, and (4) shortest healing and overall treatment times27  are objectives for implant treatment by today's standards.

Initial tissue thickness at the crest has a significant influence on marginal bone stability. If the tissue is ≤2 mm, crestal bone loss up to 1.45 mm may occur despite a supra-crestal position of the implant abutment interface.13 

Finally, some specific conditions should be respected:

  • The patient should be informed about the treatment plan and understand the need to respect the necessity for thorough daily oral hygiene at home and regular oral hygiene visits at the dental office. Any periodontal disease should be diagnosed, treated, and controlled before initiating dental implant therapy

  • Prior to surgery, several local factors must be considered: (1) optimal bone volume, (2) adequate thickness/height of soft tissue, (3) implant characteristics, and (4) connection type that dictates implant placement depth.

  • It has been demonstrated that if there is at least 3 mm of vertical soft tissue thickness and the implant is placed in the appropriate position, as dictated by its design, surgical bone stability will be achieved.

  • Prosthetic factors affecting bone stability include screw-retained restoration, titanium bases with ideal emergence profiles, and polished zirconia in subgingival areas for promoting epithelial adherence.

In conclusion, there is not 1 factor more important than another for ensuring crestal bone stability. It is the combination and interaction of factors that determines the outcome. It is only through accepting this multifactorial reality that clinicians can change their critical thinking and begin maintaining the peri-implant bone and soft tissue levels.

The new concept modality in implant treatment named WHS soft tissue management creates the necessary conditions for the creation and maintenance of a protective peri-implant soft tissue. WHS soft tissue management in combination with regular oral hygiene maintenance assures the mucogingival- and osseo-integration of the implant(s) in both short- and long-term perspectives.

The authors declare no conflicts of interest.

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