Background: Besides the osseous implant bed special significance is also attributed not only to the peri-implant tissue, but also to the function of implant-supported restorations in terms of aesthetics. No consensus is found in international literature on the significance of peri-implant soft tissue with regard to the health of peri-implant tissue. This survey paper thus aims at critically reviewing the current literature in connection with the significance of peri-implant soft tissue in consideration of aesthetics and function of restorations in the field of dental implantology and in the next step to provide examples of surgical soft-tissue augmentation.
Results: Sufficient soft-tissue management seems to have a positive influence on the aesthetic appearance of implant-supported restorations in particular in the front tooth region. In the case of progressive resorptive processes and facial contour defects, the result can be improved in particular with regard to the red-white aesthetic balance. Novel meta analyses reflect that the existence of bleeding on probing can be reduced by soft-tissue thickening and that at the same time less bone resorption is documented. With regard to surgical techniques and materials not only autologous transplants, but also promising collagen-based biomaterials are available.
Consequences: Soft tissue management should be included in planning treatment at an early point in time, in order to avoid biological complications and to achieve the best possible aesthetic result.
Keywords: Aesthetics; soft tissue; connective tissue transplants; collagen matrix; keratinised mucosa
Citation: Lorenz J, Rathe F, Schwarz F, Ghanaati S, Sader R: Peri-implant soft tissue. Significance and management in terms of function and aestetics. Z Zahnärztl Implantol 2020; 36: 16–22
Replacing a missing tooth or a tooth that is not worth restoring in general represents a challenge for the complete team of dental specialists who focus on achieving not only a functional, but also on an aesthetically appealing and satisfactory result. Special significance is attributed to the proportional and homogenous alignment between the tissue involved as well as the structures, such as hard- and soft tissue, implant and the supraconstruction.
In particular in the front tooth region of the maxilla, considerable resorptive processes take place following loss of a tooth and which – at the same time – affect the in general extremely thin buccal bone lamella to a particularly large extent [1, 5]. For this reason special focus was placed on maintaining and regenerating the osseous implant bed in the previous years and decades in order to achieve a osseous anchoring of the implant with a simultaneous optimal prosthetic implant position. The possible options to maintain and/or regenerate the buccal bone range from Socket/Ridge Preservation  to a simultaneous Guided Bone Regeneration (GBR) . A sufficient bone bed creates the foundation for the surrounding soft tissue and thus for the long-term health of the peri-implant tissue .
Besides the osseous implant bed, special significance is attributed to the peri-implant soft tissue in terms of the aesthetic appearance of implant-supported restorations. Only a harmonious scalloped structure of the marginal mucosa with the suprastructure of the implant as well as the development of a papilla filling the interdental space provide a natural result. In addition thereto, a well-developed soft tissue structure with a sufficiently wide layer of keratinised mucosa represent a barrier for plaque and oral microorganisms. As opposed to the keratinised mucosa, in particular a mobile, non-connected non-keratinised mucosa represents a risk factor for penetrating microorganisms and thus for the development of an inflammatory reaction .
The significance of peri-implant soft tissue for the long-term implant health and the aesthetic result of implant-supported restorations was investigated and discussed extensively in the previous years. For example, the Osteology-Consensus-Conference stated that by soft tissue augmentation a reduction of the gingiva and plaque indexes can be achieved. In addition thereto, implants show a significantly lower marginal bone resoption following a Connective Tissue Graft (CTG) than implants without soft tissue thickening. No significant influence of soft tissue augmentation was documented on Bleeding on Probing (BoP) and probing depth .
For the purpose of compensating soft tissue defects the autologous connective tissue graft (CTG) is described as standard procedure in international literature. In general, the connective tissue is extracted from the palate or from the tuber region and positioned in the submucosa in the recipient region. With the help of CTG it seems to be possible to improve the soft-tissue contour and thickness [7, 9, 26, 30]. In two randomised controlled trials, CTG led to a reduced mucosa recession after one year [19, 31]. In addition thereto, trials indicate a positive result of connective tissue grafting on the preservation of the soft tissue contour. CTG thus serves to prevent the development of a soft tissue deficit [24, 33]. In literature, evidence questioning the therapeutic benefit of connective tissue grafting is, however, identified. In a retrospective trial, for example, no significant increase of the soft tissue volume following a connective tissue graft was documented in a 5-year post-intervention period .
As an alternative to autologous connective tissue grafting, largely xenogenic, and also allogenic substitute materials are available. The xenogenic substitute materials mainly applied in Germany are generally classified as collagen matrixes. They reduce the risk of donor site complications as no tissue is extracted, thus making a second surgical intervention unnecessary [10, 21]. In addition thereto, the duration of surgery is reduced by using such materials. These three-dimensional collagen matrixes differ from collagen membranes with regard to their composition, structure and field of application. In literature sufficient evidence is found to show that with the help of xenogenic collagen matrixes results which are comparable with autologous CTG can be achieved [16, 27, 32]. Long-term studies describing the positive influence of a collagen matrix on the aesthetic result of an implant-supported restoration are also available . With regard to comparing the autologous connective tissue graft with the xenogenic collagen matrix, both processes seem to be able to achieve similar results . No consensus in international literature can, however, be found in that respect .
The role of keratinised mucosa is also the subject matter of many examinations in international literature. Over the past years the question has been raised as to whether a certain width of keratinised mucosa is required to ensure a long-term health of the peri-implant tissue. Based on an examination by Lang and Löe on natural teeth which was carried out in 1972 an “adequate width” of the keratinised mucosa, namely of ≥≥ 2 mm, was defined . As the peri-implant soft tissue in anatomy differs considerably from dental tissue, it is doubtful whether 2 mm of keratinised mucosa will also suffice around implants or are at all necessary. The soft tissue among others at the implant is only held in position by a hemidesmosomal attachment. The current data situation, however, suggests that the oral hygiene measures will be favoured by the existence of a sufficiently dimensioned mucosa (> 2 mm) .
The width of the keratinised mucosa can be enhanced by autologous grafts (free mucosal grafts) or by combining allogenic and xenogenic grafts with advanced apically positioned flaps. The oral vestibuloplasty in combination with a free gingiva graft, analogue to soft tissue thickening by connective tissue grafting is regarded as the gold standard. In this indication, organic materials in the form of collagen matrixes are, however, also found as an alternative to the autologous tissue graft. In a clinical trial, comparing the three-dimensional collagen matrix Mucograft (Geistlich Biomaterials, Wolhusen, Switzerland) in the case of an comparable percentage shrinkage of the keratinised gingiva over a period of 90 days is documented (collagen matrix: 32.98 %; free graft: 28.35 %) . In addition thereto, comparing the three-dimensional collagen matrix with the free graft reflected an improved adaptation of the collagen matrix to the surrounding tissue than in the case of the graft which was clearly separated from the surrounding tissue .
Possibilities of soft tissue augmentation
Soft tissue thickening
Soft tissue thickening for the purpose of improving the alveolar ridge contour or in the case of a thin phenotype is primarily achieved by the augmentation of autologous subepithelial connective tissue or with xenogenic collagen matrixes. For both procedures a comparable recipient bed preparation is required. The key difference between the autologous CTG and the use of a collagen matrix is that, in the case of CTG, an extraction of tissue is necessary. This step can be avoided by using collagen matrixes.
With regard to the point in time of soft tissue thickening various options are available. These range from a pre-implant soft tissue augmentation to a soft tissue augmentation at the point in time of uncovering the implant. The key surgical steps in both cases are similar.
Following local anaesthesia a ridge incision is performed in with marginal relief in the region of the adjacent teeth. In the case of soft tissue augmentation at the point in time of uncovering the implant, a mucoperiosteal flap is raised in the crestal region to present the implant. At the transition between the crestal and the buccal alveolar process a split flap preparation is performed in buccal direction in order to avoid periostomy.
This can be performed with a “sharp” incision, e.g. by using a suitable scalpel. By preparing the split flap a pocket is created which can be used to incorporate an autologous connective tissue transplant or a collagen matrix.
In the following an overview is given of the methods of soft tissue thickening with autologous connective tissue graft (a) and with a collagen membrane (b):
a) Autologous connective tissue grafting: Preparation of the recipient region by forming a split flap and a submucous envelope in soft tissue thickening by autologous connective tissue grafting is followed by connective tissue extraction. This is possible not only in the tuber region, but also from the palate. Following local anaesthesia an appropriately dimensioned connective tissue graft is extracted according to the recipient region by means of undermining preparation. In comparison with removal of a free mucosal graft no harvesting of superficial keratinised mucosa is necessary. In general, it is necessary to ensure a correct localisation of the harvesting localisation, appropriate dimensioning and to take the course of key anatomic structures into consideration. Due to subepithelial harvesting of the connective tissue transplant, a primary wound closure is feasible.
Figures 1–5 show a buccal soft tissue thickening by autologous connective tissue grafting on 2 implants in region 21 and 22 at the point in time of uncovering the implant.
b) Xenogenic collagen matrixes: The use of xenogenic collagen matrixes for the purpose of thickening the peri-implant soft tissue represents a promising approach in order to reduce discomfort of the patient by extracting connective tissue at the palate or in the tuber region. Figures 6–10 show buccal soft tissue thickening with the volume-stable three-dimensional collagen matrix FibroGide (Geistlich Biomaterials, Wolhusen, Switzerland) at an implant in region 12 at the point in time of uncovering the implant for the purpose of augmenting a buccal contour defect.
The surgical intervention in the area of the recipient region primarily corresponds to the procedure in autologous connective tissue grafting. By preparing the split flap a "pocket" is created for the incorporation of the collagen matrix. The size of the pocket should be slightly over-dimensioned in comparison with the collagen matrix to be inserted. In the next step the collagen matrix is contoured according to the defect and then inserted into the previously prepared pocket. For the purpose of fixing and immobilising the collagen matrix it is possible to insert a palatinal mattress suture. In the next step the wound is closed by a combination of mattress sutures and single sutures.
In connection with the use of a collagen matrix some key material properties should be taken into account. The collagen matrix is an elastic biomaterial with a stable form which can be manually compressed, but returns to its original form after being compressed. For this reason it is necessary to ensure a careful adaptation to the size and contour of the matrix, as well as a tension-free wound management.
Widening the keratinised mucosa
Various techniques are described for the purpose of widening the keratinised mucosa. One of the most frequently applied techniques is the vestibuloplasty in combination with a free gingiva graft or a collagen matrix. In this procedure a crestal incision is performed in the area of the attached keratinised mucosa. In the next step the slit flap is then carefully prepared in apical direction to avoid periostomy or flap perforation. A sufficient preparation in apical direction is necessary to achieve an apical shift of the mucosa. In the next step the mucosa is attached as far as possible in apical direction by using periosteal sutures. The distance created in this method circumscribes the width of newly created keratinized peri-implant mucosa.
Various wound management possibilities are available to cover the free wound area. Free granulation is associated with considerable shrinkage. It is alternatively possible to cover the wound area with a free gingiva graft which is taken from the gum. It is thereby possible to reduce shrinkage and achieve a keratinisation. As an alternative to extracting a free gingiva graft, it is possible to use a collagen matrix. The widespread and extensively investigated xenogenic collagen matrix Mucograft (Geistlich Biomaterials, Wolhusen, Switzerland) e.g. has a two-layer structure. The compact structure provides stability and enables an open implant healing, whereas the spongy structure contributes to stability and growth of soft tissue cells.
Following loss of a tooth, physiological transformation processes initially lead to a bone resorption which primarily takes place in the buccal region and to a reduction of the keratinised mucosa. The consequence of such a development is that in the following implant insertion in this area, a lower width and thickness of keratinised mucosa is given than prior to loss of the tooth . This situation is aggravated by the fact that with regard to the peri-implant soft tissue a coronal mobilisation of the soft tissue flap is required in connection with the osseous augmentation, and that thus the mucogingival line is displaced as a result.
With regard to the significance of the peri-implant soft tissue it was possible to indicate that patients with thick morphotypes require fewer recessions at the implant and more interdental soft tissue filling (papilla) . Furthermore, it was shown that thickening peri-implant soft tissue is possible not only with connective tissue grafts , but also with a collagen matrix. In both procedures it was indicated that formerly thin tissue which was thickened reflects significantly less peri-implant bone loss [14, 15].
Meta analyses in international literature document on the one hand inconsistent statements regarding the significance of peri-implant soft tissue. A systematic review of Wennström and Derks indicates that on the grounds of the heterogeneity of the underlying trials no statistical analysis of the source data was possible. The existence of sufficient keratinised mucosa has a positive influence on the plaque index, the effect of Bleeding on Probing was, however, inconsistent. Furthermore, no statistically significant influence of the existence of keratinised mucosa  with regard to the development of recessions and peri-implant bone loss was documented. With regard to the effect of soft tissue augmentation a further systematic review and meta-analysis furthermore revealed that a thickening of soft tissue has a positive influence on the width and thickness of the keratinised mucosa and the existence of Bleeding on Probing and thus less bone resorption is identified .
Although there are inconsistent statements on the significance of peri-implant soft tissue in literature, as well as on the effect of soft tissue augmentation, the most recent literature nevertheless indicates in particular that sufficient soft tissue management has a positive effect on aesthetics and the long-term stability of the peri-implant tissue and may prevent the development of peri-implant mucositis and peri-implantitis. Soft tissue management should therefore be included in the treatment plan at an early point in time to avoid biological complications and to ensure that the best possible aesthetic result will be achieved.
Conflicts of interest: The authors state that no conflicts of interest exist in connection with this article. In addition thereto, the authors state the following:PD Dr. Jonas Lorenz received a remuneration and compensation of his travel expenses for speeches at Geistlich (manufacturer of biomaterials), the associations DGI and DGÄZ and at the Berufsverband der Landeszahnärztekammer Hessen. Dr. Florian Rathe has no conflicts of interest. Prof. Dr. Frank Schwarz is a honorary member of the Osteology Board. Prof. Dr. Dr. Shahram Ghanaati has not stated any conflicts of interest. Prof. Dr. Dr. Robert Sader receives an expense allowance as DGÄZ-President and received a remuneration for speeches from Camlog, Mectron, Geistlich and Straumann. ■
- Albrektsson T, Branemark P, Hansson, Lindstrom J: Osseointegrated titanium implants. Requirements for ensuring a long-lasting, direct bone-to-implant anchorage in man. Acta Orthopaedica Scandinavica 1981; 52: 155–170
- Araujo M, Lindhe J: Dimensional ridge alterations following tooth extraction. An experimental study in the dog. J Clin Periodontol 2005; 32: 212–218
- Bienz SP, Jung RE, Sapata VM, Hämmerle CHF, Husler J, Thoma DS: Volumetric changes and peri-implant health at implant sites with or without soft tissue grafting in the esthetic zone, a retrospective case-control study with a 5-year follow-up. Clin Oral Implants Res 2017; 28: 1459–1465
- Cairo F, Barbato L, Tonelli P, Batalocco G, Pagavino G, Nieri M: Xenogeneic collagen matrix versus connective tissue graft for buccal soft tissue augmentation at implant site. A randomized, con- trolled clinical trial. J Clin Periodontol 2017; 44: 769–776
- Cardaropoli G, Araujo M, Lindhe J: Dynamics of bone tissue formation in tooth extraction sites. An experimental study in dogs. J Clin Periodont 2003; 30, 809–818
- Chappuis V, Rahman L, Buser R, Janner SFM, Belser UC, Buser D: Effectiveness of Contour Augmentation with Guided Bone Regeneration: 10-Year Results. J Dent Res 2018; 97: 266–274
- De Bruyckere T, Eghbali A, Younes F, De Bruyn H, Cosyn J: Horizontal stability of connective tissue grafts at the buccal aspect of single implants: a 1-year prospective case series. J Clin Periodontol 2015; 42: 876–882
- Giannobile WV, Jung RE, Schwarz F: on behalf of the Groups of the 2nd Osteology Foundation Consensus Meeting. Evidence-based knowledge on the aesthetics and maintenance of peri-implant soft tissues: Osteology Foundation Consensus Report Part 1 – Effects of Soft Tissue Augmentation Procedures on the Maintenance of Peri-implant Soft Tissue Health. Clin Oral Impl Res 2018; 29: 7–10
- Hanser T, Khoury F: Alveolar Ridge Contouring with Free Connective Tissue Graft at Implant Placement: a 5-Year Consecutive Clinical Study. Int J Periodontics Restorative Dent 2016; 36: 465– 473
- Herford AS, Akin L, Cicciu M, Maiorana C, Boyne PJ: Use of a porcine collagen matrix as an alternative to autogenous tissue for grafting oral soft tissue defects. J Oral Maxillofac Surg 2010; 68: 1463–1470
- Kan J, Rungcharassaeng K, Umezu Ki, Kois J: Dimensions of peri-implant mucosa. An evaluation of maxillary anterior single implants in humans. J Periodontol 2003; 74: 557–562
- Lang NP, Löe H: The relationship between the width of keratinized gingiva and gingival health. In: J Periodontol 1972; 43: 623–627
- Lin GH, Chan HL, Wang HL: The significance of keratinized mucosa on implant health: a systematic review. J Periodontol 2013; 84: 1755–1767
- Linkevicius T, Puisys A, Linkeviciene L, Peciuliene V, Schlee M: Crestal Bone Stability around Implants with Horizontally Matching Connection after Soft Tissue Thickening: A Prospective Clinical Trial. In: Clin Implant Dent Relat Res 2015; 17: 497–508
- Linkevicius T, Puisys A, Steigmann M, Vindasiute E, Linkeviciene L: Influence of Vertical Soft Tissue Thickness on Crestal Bone Changes Around Implants with Platform Switching: A Comparative Clinical Study. In: Clin Implant Dent Relat Res 2015; 17: 1228–1236
- Lorenzo R, Garcia V, Orsini M, Martin C, Sanz M: Clinical efficacy of a xenogeneic collagen matrix in augmenting keratinized mucosa around implants: a randomized controlled prospective clinical trial. Clin Oral Implants Res 2012; 23: 316–324
- Maiorana C, Pivetti L, Signorino F, Grossi GB, Herford AS, Beretta M: The efficacy of a porcine collagen matrix in keratinized tis- sue augmentation: a 5-year follow-up study. Int J Implant Dent 2018; 4,1
- Mericske-Stern R, Steinlin Schaffner T, Marti P, Geering A: Peri-implant mucosal aspects of ITI implants supporting overdentures. A five-year longitudinal study. Clin Oral Implants Res 1994; 5: 9–18
- Migliorati M, Amorfini L, Signori A, Biavati AS, Benedicenti S: Clinical and aesthetic outcome with post-extractive implants with or without soft tissue augmentation: A 2-year randomized clinical trial. Clin Implant Dent Relat Res 2015; 5: 983–995
- Roccuzzo M, Gaudioso L, Bunino M, Dalmasso P: Long-term stability of soft tissues following alveolar ridge preservation: 10-year results of a prospective study around nonsubmerged implants. Int J Periodontics Restorative Dent 2014; 34: 795– 804
- Sanz M, Lorenzo R, Aranda J, Martin C, Orsini M: Clinical evaluation of a new collagen matrix (Mucograft prototype) to enhance the width of keratinized tissue in patients with fixed prosthetic restora- tions: a randomized prospective clinical trial. J Clin Periodontol 2009; 36: 868–876
- Schmitt CM, Tudor C, Kiener K et al.: Vestibuloplasty: porcine collagen matrix versus free gingival graft: a clinical and histologic study. J Periodontol 2013; 84: 914–923
- Schmitt CM, Moest T, Lutz R, Wehrhan F, Neukam FW, Schlegel KA: Long-term outcomes after vestibuloplasty with a por- cine collagen matrix (Mucograft®) versus the free gingival graft: a comparative prospective clinical trial. Clin Oral Implants Res 2016; 27: 125–133
- Schneider D, Grunder U, Ender A, Hämmerle CHF, Jung RE: Volume gain and stability of peri-implant tissue following bone and soft tissue augmentation: 1-year results from a prospective cohort study. Clin Oral Implants Res 2011; 22: 28–37
- Schwarz F, Becker J: DGZMK Leitlinie (S3) Die Behandlung periimplantärer Infektionen an Zahnimplantaten. AWMF-Registernummer: 083–023. Mai 2016
- Stefanini M, Felice P, Mazzotti C, Marzadori M, Gherlone EF, Zucchelli G: Transmucosal Implant Placement with Submarginal Connective Tissue Graft in Area of Shallow Buccal Bone Dehiscence: a Three-Year Follow-Up Case Series. Int J Periodontics Restorative Dent 2016; 36: 621–630
- Thoma DS, Zeltner M, Hilbe M, Hämmerle CHF, Husler J, Jung RE: Randomized controlled clinical study evaluating effectiveness and safety of a volume-stable collagen matrix compared to autogenous connective tissue grafts for soft tissue augmentation at implant sites. J Clin Periodontol 2016; 43: 874–885
- Thoma D, Naenni N, Figuero E et al.: Effects of soft tissue augmentation procedures on peri-implant health or disease: A systematic review and meta-analysis. Clin Oral Implants Res 2018; 29: 32–49
- Wennström J, Derks J: Is there a need for keratinized mucosa around implants to maintain health and tissue stability? Clinical oral implants research 2012; 23: 136–146
- Wiesner G, Esposito M, Worthington H, Schlee M: Connective tissue grafts for thickening peri-implant tissues at implant placement. One-year results from an explanatory split-mouth randomised controlled clinical trial. Eur J Oral Implantol 2010; 3: 27–35
- Yoshino S, Kan J, Rungcharassaeng K, Roe P, Lozada J: Effects of connective tissue grafting on the facial gingival level following single immediate implant placement and provisionalization in the esthetic zone: A 1-year randomized controlled prospective study. Int J Oral Maxillofac Implants 2014; 2: 432–440
- Zeltner M, Jung RE, Hämmerle CHF, Hüsler J, Thoma DS: Randomized controlled clinical study comparing a volume-stable collagen matrix to autogenous connective tissue grafts for soft tissue augmentation at implant sites: linear volumetric soft tissue changes up to 3 months. J Clin Periodontol 2017; 44: 446–453
- Zuiderveld EG, Meijer HJA, den Hartog L, Vissink A, Raghoebar GM: Effect of connective tissue grafting on peri-implant tissue in single immediate implant sites: a RCT. J Clin Periodontol 2018; 45: 253–264
- Lorenz J, Sader R, Ghanaati S: Vestibulumplastik mit einer 3D-Kollagenmatrix. BDIZ EDI konkret 3/2018, 66–68