The peri-implant soft-tissue phenotype includes keratinized mucosa width, mucosal thickness, and supracrestal tissue height. These dimensions jointly influence plaque control, soft-tissue stability, implant surface exposure, and esthetic outcomes. A practical threshold of less than 2 mm (thin) versus 2 mm or greater (thick) mucosa is frequently adopted for clinical decision making and research reporting.

Peri-implant soft tissues create the only biological barrier against bacterial penetration into the underlying tissues and bone. Compared with teeth, dental implants lack a periodontal ligament and its rich vascular network. This reduced vascularity means soft tissues around implants are more susceptible to biofilm-induced inflammation, leading to mucosal breakdown if hygiene is inadequate. A healthy mucosal cuff improves long-term implant stability, contributes to patient comfort during function and hygiene, and plays a major role in esthetics in the visible zone.

A robust band of peri-implant mucosa also supports prosthetic longevity by minimizing mechanical trauma from appliances or brushing and by helping maintain a tight epithelial seal against microbial ingress.

In an experimental canine model, it was demonstrated that the resection of the entire band of keratinized mucosa at the time of implant placement leads to significantly greater marginal bone loss, even in sites with initially thick buccal alveolar bone (≥2 mm). This suggests that the mucosal phenotype is perhaps more important than the bone phenotype for long-term peri-implant bone stability.

Because keratinized mucosa is typically both thicker and its epithelial layer is keratinized, the findings from the 2014 study did not distinguish whether its protective effect on crestal bone was attributable to surface keratinization or to tissue thickness. To clarify this relationship, Berglundh and Lindhe ^, used an experimental canine model in which implants were placed in sites with normal mucosal thickness or in sites where the connective tissue was surgically thinned before healing. Despite retention of keratinization, the thin-tissue sites experienced consistent crestal bone resorption, indicating that mucosal thickness is the primary determinant of establishing and maintaining supracrestal soft-tissue attachment. This supports the concept that a minimum vertical mucosal dimension of approximately 3 mm is required for biological stability, a finding that has since been corroborated in clinical research.

Further evidence supporting the dominant role of mucosal thickness comes from an experimental study by Bengazi and colleagues In sites where the native keratinized mucosa had been removed, augmentation using either a free gingival graft (retaining keratinized epithelium) or a de-epithelialized connective tissue graft (CTG) resulted in similar stability of peri-implant soft-tissue margins and crestal bone levels. Importantly, although the healed mucosa in both groups remained nonkeratinized, the increase in mucosal thickness alone was sufficient to significantly reduce marginal bone loss.

Soft-tissue thickness plays a critical role in stabilizing peri-implant bone and gingival architecture. When adequate thickness is present, the absence of keratinization alone may not predispose implants to increased bone loss or recession. In other words, phenotype modification that increases tissue thickness can successfully offset the biological vulnerability associated with minimal or absent keratinized mucosa.

The interplay between peri-implant mucosa and bone has been clearly demonstrated by the experiments above.

Key relationships:

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  Thin mucosa often triggers bone resorption until adequate tissue height is attained to establish supracrestal attachment

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  Lack of keratinization is not associated with marginal bone loss as long as mucosal thickness is preserved

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  Soft-tissue augmentation may reduce future bone remodeling risk

  • Clinical guidelines:

• A minimum of 3 mm of mucosal thickness is currently considered biologically protective in most implant sites.

Ideal implant positioning supports stable bone and soft-tissue contours. A facially malpositioned implant means insufficient bone thickness, often requiring bone and/or soft-tissue grafting to prevent thread exposure that may lead to peri-implantitis or at a minimum, recession.

Clinical data have demonstrated that initial soft-tissue thickness is a critical determinant of peri-implant bone remodeling. Implants placed in thin mucosa experienced greater marginal bone loss during re-establishment of supracrestal attachment, particularly when implants were positioned equicrestal compared with subcrestally positioned implants. Thicker mucosa provided a protective effect by reducing early bone resorption around the implant neck.

Long-term clinical findings reinforce the importance of adapting implant depth to the peri-implant soft-tissue phenotype. In a split-mouth clinical trial with 2-year and subsequent 5-year follow-up, implants placed subcrestally demonstrated superior marginal bone level stability compared with equicrestal implants. Early exposure of the implant surface in equicrestal placements was associated with additional bone remodeling, supporting the recommendation to position implants deeper when soft tissues are thin. Subcrestal placement in such cases effectively compensates by allowing greater soft-tissue height for supracrestal attachment formation.

These results are consistent with a recent controlled clinical trial examining implant depth, abutment height, and soft-tissue phenotype. ^, Implants placed approximately 2 mm subcrestally and restored with longer abutments (>2 mm) exhibited the least marginal bone loss. Regression modeling identified abutment height as the strongest predictor of bone remodeling, followed by vertical implant position, highlighting the critical interplay between implant placement depth and soft-tissue dimensions.

Thin peri-implant mucosa may be unable to accommodate a stable supracrestal soft-tissue seal without compensatory marginal bone loss, which risks early implant surface exposure. Increasing tissue thickness enhances the soft-tissue barrier, supports a coronal marginal position, and improves color masking and emergence-profile control in the esthetic zone.

Although keratinized mucocal width facilitates comfortable hygiene and reduces mucosal inflammation in functionally demanding regions, the color and texture mismatch of free gingival graft can compromise esthetics in the anterior region. Phenotype modification therefore should be site specific, balancing function and esthetics.

Augmentation at second stage or at the time of implant placement can reduce the need for larger corrective surgeries later.

The surgical procedure for mucosal augmentation has traditionally been performed using flap surgery. The vestibular incision subperiosteal tunnel access (VISTA) has been introduced with a number of biological and surgical advantages. The vestibular access provides a convenient method to provide surgical access for mucosal graft placement. Subperiosteal tunneling preserves the blood supply by preserving the mucoperiosteal complex. This also preserves surface color and texture of the mucosa. Lack of surface incision, particularly avoiding detachment of papilla, can accomplish far better esthetic outcomes, especially to manage pre-existing esthetic complications.

An alternative to free gingival grafting in the nonesthetic regions for vestibular extension is the FIVE (fibrin immobilization vestibular extension) technique. ^, This entails apical positioning of a flap and its stabilization using fixation screws. It is best if the initial incision is in the keratinized mucosa so that the coronal and apical borders of the flap have keratinized mucosa. In this way, keratinized mucosa will migrate from the coronal and apical keratinized mucosal borders to fill the space in between. To protect the exposed bone surfaces, solid matrix platelet-rich fibrin is immobilized onto the bone using fixation screws. This technique has been demonstrated to achieve approximately 4 mm of increase in the zone of keratinized mucosa. This is approximately the same magnitude as free gingival grafting.

In anterior region with high esthetic demand, thin mucosal thickness is best managed with CTGs or soft-tissue substitutes such as collagen or dermal matrices delivered via minimally invasive techniques (eg, VISTA). This approach enables phenotype modification while preserving the native surface color and texture of the peri-implant mucosa. In posterior or nonesthetic regions, subcrestal implant placement helps provide sufficient vertical tissue height for stable supracrestal attachment, and soft-tissue thickening may be achieved using CTGs or biomaterial scaffolds. When increased vestibular depth and a wider band of keratinized mucosa are required, free gingival grafting remains a predictable solution. The FIVE technique offers a minimally invasive alternative for vestibular extension with comparable gains in keratinized mucosa.

A 78 year old patient presented with a long history of partial denture use and expressed a strong preference for a fixed implant-supported solution. Her medical history included hypertension and hypercholesterolemia, both well controlled, and she was otherwise healthy. Clinical and radiographic evaluation revealed combined horizontal and vertical ridge atrophy; however, sufficient residual bone volume remained to accommodate implants placed in a more apical 3 dimensional position. Soft-tissue assessment identified a thin mucosal phenotype, raising concerns regarding long-term peri-implant stability.

Given the patient’s age and preference for a minimally invasive approach, a decision was made to proceed with implant placement in native bone without prior augmentation. The implants were installed using a 2 stage surgical protocol with 4 mm narrow healing abutments, which were completely submerged beneath the mucosal flap. Due to the thin mucosa, the implants were intentionally positioned subcrestally to promote the development of a stable supracrestal soft-tissue complex. Early healing was uneventful ( Fig. 3 A).

( A – J ) Clinical sequence of peri-implant soft-tissue phenotype modification using the FIVE technique. ( A ) Uneventful early healing following 2 stage subcrestal implant placement with submerged 4 mm narrow healing abutments. ( B ) Crestal incision designed to bisect the band of keratinized mucosa, preserving keratinized tissue on both buccal and lingual flap margins. ( C ) Apical positioning of the mucosal flap stabilized using modular tenting screws. ( D , E ) Preparation of PRF biomaterials: compressed solid PRF membranes fused with liquid PRF to form a thick, cohesive membrane. Removal of submerged healing abutments and placement of the thick PRF membrane over the ridge. ( G ) Insertion of longer healing abutments through the PRF membrane, providing stabilization at the implant platforms. ( H ) Apically positioned flap retained using wide tenting screws placed through the apical perforations. ( I ) Soft-tissue maturation at 4 weeks showing increased vestibular depth and immature attached mucosa. ( J ) Healthy peri-implant mucosa following delivery of the definitive zirconia prosthesis, demonstrating functional stability despite a minimal band of attached tissue.

The primary soft-tissue concerns included the thin mucosal phenotype and limited vestibular depth. To address these issues while maintaining a minimally invasive philosophy, the FIVE technique was selected. A midcrestal incision was designed to bisect the band of existing keratinized mucosa, ensuring that both the buccal and lingual flap margins retained keratinized tissue ( Fig. 3 B). The flap was then apically positioned and secured using modular tenting screws ( Fig. 3 C).

Two platelet-rich fibrin (PRF) preparations were produced—liquid and solid matrix. The solid PRF clots were compressed into membranes and subsequently fused with liquid PRF to create a large, thick, cohesive PRF membrane ( Fig. 3 D, E). After removing the submerged healing abutments, the PRF membrane was draped over the ridge to biologically enhance soft-tissue maturation ( Fig. 3 F). Longer healing abutments were inserted through the PRF membrane, mechanically stabilizing it at the implant platforms ( Fig. 3 G). The apically positioned flap was perforated over the apically placed tenting screws, and wide screw heads were used to retain the flap in its new position ( Fig. 3 H).

The tenting screws were removed after 2 weeks. At 4 weeks, an increased vestibular depth with early-stage attached mucosa formation was evident ( Fig. 3 I). Following delivery of the definitive zirconia prosthesis, healthy peri-implant mucosa was present with a stable, functional tissue margin ( Fig. 3 J). Although the band of attached mucosa remained narrow, the combination of subcrestal implant placement, improved mucosal thickness, and functional keratinized tissue was sufficient to support long-term peri-implant health in this patient.