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Anatomy of the Peri‐implant Soft Tissues

Anton Sculean1, Edward Pat Allen2, Dieter D. Bosshardt1,3, and Georgios E. Romanos4

1 Department of Periodontology, University of Bern, Bern, Switzerland

2 Center for Advanced Dental Education, Dallas, TX, USA

3 Robert K. Schenk Laboratory for Oral Histology, School of Dental Medicine, University of Bern, Bern, Switzerland

4 Department of Periodontics and Endodontics, School of Dental Medicine, Stony Brook University, Stony Brook, NY, USA

Dental implants anchor into the jawbone through direct contact between the bone and the implant, a process known as “osseointegration.” Recent evidence suggests that the sustained success and survival of implants are not exclusively contingent on “osseointegration” but also on the soft tissues enveloping the transmucosal section of the implant, which serves as a barrier between the peri‐implant bone and the oral cavity (Figure 1.1). This soft tissue seal, often referred to as the “peri‐implant mucosa,” plays a crucial role in the overall health and longevity of dental implants [1]. The attachment of soft tissue to the implant functions as a biological seal, ensuring optimal conditions and thwarting the onset of peri‐implant infections, such as peri‐implant mucositis and peri‐implantitis. Consequently, the peri‐implant soft tissues play a pivotal role in ensuring the long‐term survival of implants [1].

As soft tissue develops around teeth during tooth eruption, it forms a seal that protects the supporting tissues – namely, the alveolar bone, periodontal ligament, and cementum – from exposure to the oral cavity [2]. In contrast, the peri‐implant mucosa is established after the oral soft and hard tissues undergo a healing process to accommodate the osseointegrated implants. The following section provides a concise overview of the key anatomical features of peri‐implant tissues.

Structure of Peri‐implant Tissues in Health

During the process of wound healing following the accommodation of dental implants, the features of the peri‐implant mucosa are established [3] (Figures 1.2–1.4). Berglundh et al. [4] conducted an examination in dogs to investigate the anatomical and histological features of the peri‐implant mucosa formed in a two‐stage procedure, comparing them with the gingiva around teeth.

It was revealed that the peri‐implant mucosa consists of a keratinized oral epithelium located at the external surface. This epithelium is connected to a thin non‐keratinized sulcular epithelium facing the abutment and terminating in junctional epithelium, equivalent to the junctional epithelium around teeth, termed as peri‐implant junctional epithelium. The peri‐implant junctional epithelium terminates 2 mm apical to the coronal soft tissue margin and 1.0–1.5 mm coronal to the peri‐implant bone crest. The mean supracrestal soft tissue, including sulcus depth, measured 3.80 mm around implants and 3.17 mm around teeth (Figures 1.2–1.4).

While no statistically significant difference was observed in the height of the junctional epithelium and sulcus depth between implants and teeth, the height of the soft connective tissue was statistically significantly greater around implants than around teeth. The peri‐implant junctional epithelium and the soft connective tissue adjacent to the abutment appeared to be in direct contact with the implant–abutment surface [4].

In summary, this study demonstrated that the peri‐implant mucosa exhibits comparable anatomical features to those of gingiva around teeth [4].

Subsequent studies provided evidence that a similar mucosal attachment formed on titanium in conjunction with different implant systems [5, 6] and around intentionally non‐submerged and initially submerged implants [7, 8, 9]. However, the peri‐implant junctional epithelium was significantly longer in initially submerged implants to which an abutment was connected later than in intentionally non‐submerged implants [9].

Figure 1.1 Clinical image depicting a healthy soft tissue around an osseointegrated implant.

Source: Photo: Prof. Dr. Georgios Romanos.

Figure 1.2 Photomigrograph of an osseointegrated titanium dental implant depicting the direct bone‐implant contact and the supracrestal soft tissue implant contact.

Source: Photo: Prof. Dieter D. Bosshardt.

Figure 1.3 Higher magnification depicting the supracrestal peri‐implant soft tissues consisting of oral and sulcular epithelium and connective tissue adhesion to the implant surface.

Source: Photo: Prof. Dieter D. Bosshardt.

The biologic width (i.e., the supracrestal soft tissue) was revisited in a further dog experiment after abutment connection to the implant fixture with or without a reduced vertical dimension of the oral mucosa (Berglundh and Lindhe [10]). While the peri‐implant junctional epithelium was about 2 mm long, the supra‐alveolar soft connective tissue was about 1.3–1.8 mm high. Interestingly, sites with a reduced mucosal thickness consistently revealed marginal bone resorption, adjusting the width of the supracrestal soft tissue. Evaluating the biologic width around one‐ and two‐piece titanium implants that healed either non‐submerged or submerged in dog mandibles, Hermann et al. [11] suggested that the gingival margin is located more coronally, and the biologic width is more like teeth in association with one‐piece non‐submerged implants compared to either two‐piece non‐submerged or two‐piece submerged implants. These findings were later confirmed in a comparably designed dog study with another implant system [12].

Several studies have evaluated the impact of surface topography (i.e., surface roughness measurements) on the peri‐implant mucosa. Cochran et al. [13] failed to show any differences in the dimensions of the sulcus depth, peri‐implant junctional epithelium, and soft connective tissue contact to implants with a titanium plasma‐sprayed (TPS) surface or a sandblasted acid‐etched surface. Abrahamsson et al. [14, 15] observed similar epithelial and soft connective tissue components on a rough (acid‐etched) and smooth (turned) titanium surface. The biologic width (i.e., supracrestal soft tissue) was greater on the rough surface; however, without a statistically significant difference from that around a smooth surface.

Figure 1.4 Higher magnification of the coronal portion of the supracrestal peri‐implant soft tissues. The oral and sulcular epithelium are clearly visible. A more diffuse inflammatory infiltrate, located immediately adjacent to the junctional and sulcular epithelium is visible.

Source: Photo: Prof. Dieter D. Bosshardt.

Findings from two human histologic studies revealed less epithelial downgrowth and a longer soft connective tissue in conjunction with oxidized or acid‐etched titanium compared to a machined surface [16]. In a study in baboons, Watzak et al. [17] showed that implant surface modifications had no significant effect on the biologic width after 18 months of functional loading. Following a healing period of 3 months, nano‐porous TiO2 coatings of one‐piece titanium implants showed a similar length of peri‐implant soft connective tissue and epithelium as the uncoated, smooth neck portion of the control titanium implants in dogs [18]. Schwarz et al. [19] suggested that soft tissue integration was more influenced by hydrophilicity than by microtopography.

Several studies revealed that the epithelial cells attach to different implant materials in a comparable way to that of the junctional epithelial cells to the tooth surface via hemidesmosomes and a basal lamina [3].

Analyzing the intact interface between soft connective tissue and titanium‐coated epoxy resin implants, the parallel orientation of collagen fibrils to the titanium layer was confirmed [20, 21]. Since implants lack a cementum layer that can invest the peri‐implant collagen fibers, the attachment of the soft connective tissue to the transmucosal portion of an implant is regarded as being weaker than the soft connective tissue attachment to the surface of a tooth root. Therefore, improving the quality of the soft tissue‐implant interface is considered to be of great relevance for maintaining healthy peri‐implant tissues [3].

Studies on the distribution of the collagen types on the peri‐implant soft tissues have been evaluated by different research groups. Chavrier et al. [22] examined collagen types I, III, and IV as well as noncollagenous glycoproteins (i.e., laminin and fibronectin), and they could not find any significant structural differences between peri‐implant mucosa and gingiva. However, Chavrier et al. [22] underlined the clinical importance of collagen type III and fibronectin in keratinized mucosa surrounding implants, because these proteins seem to promote...