Soft tissue management and bone augmentation in implantology
Soft tissue management during augmentation, implantation, and second-stage surgery
In addition to purely functional rehabilitation, the esthetic quality of implant treatments is becoming increasingly important in modern implantology. Above all, patients consider the appearance of peri-implant soft tissue and prosthetic superstructures to be decisive.181
The care and preservation of existing soft and hard tissue is, of course, essential for esthetically appealing implantology for prosthetic purposes. In many cases where tissue cannot be preserved, functional and esthetic results are not possible without bone augmentation in combination with corresponding soft tissue management. A preoperative esthetic analysis is recommended in almost all cases to ensure that the implant is positioned anatomically correctly and is presented in an optimal manner relative to the adjacent teeth and soft tissue. Soft tissue management is therefore decisive in all surgical interventions for the overall result of augmentative treatment.
According to Rosenquist,149 there are four factors that fundamentally determine the functional and esthetic appearance of soft tissue: 1) the width and position of the attached keratinized gingiva; 2) the buccal volume and contour of the alveolar process; 3) the height and profile of the gingival margin; and 4) the size and appearance of the interdental and interimplant papillae. However, esthetic results are often poorly documented in the literature and are rarely taken into account as a criterion of treatment success.16 Notwithstanding, the adequate width of the attached and/or keratinized mucosa was (and is) regularly discussed in the clinical literature. A systematic review found that the amount of plaque accumulation, mucosal inflammation, recessions, and loss of attachment were more expressed to a statistically significant extent around implants where the width of keratinized mucosa was inadequate.115,147 It has to be noted, however, that parameters such as bleeding on probing (BoP), probing depth, and radiographic bone loss may be worse if the keratinized mucosa is missing.115 In a study by Keeve and Khoury94 on a sample of 77 patients with altogether 105 implants over an average observation period of 8 years, a statistically less significant degree of plaque accumulation, recessions, and mucosal inflammation around implants with at least 2 mm of attached mucosa were observed.94 Due to the structural anatomical differences between teeth and implants, which mostly consist of missing supracrestal fibers attaching to the root in the case of titanium or ceramic surfaces, compromised transmucosal attachment can be expected around implants already after exposure.158 The best possible fixation of the mucosa surrounding implants can, at the very least, ensure better daily plaque control and reduce the related inflammatory processes.178 The keratinization of the tissue in visible areas is indispensable for esthetic reasons (e.g. with a view to the formation of recessions), and is essential for the functional and esthetic success of an implant. It is certainly recommended to create keratinized, or at least attached, mucosa of an adequate width during implantation or exposure surgery.
The other important aspect of soft tissue management is the thickness of the peri-implant mucosa. Scientific studies have proven that one should aim for a minimum height of at least 2 mm.117 A systematic review confirmed that thicker peri-implant soft tissue layers (> 2 to 3 mm) result in significantly less bone loss around implants.171,178 It is therefore reasonable to prepare not only the width but also the thickness of the attached soft tissue cuff – particularly in esthetic areas – in a manner that enables optimal long-term success rates.
The size and form of the papillae adjacent to implants are determined by anatomical, surgical, and restorative factors. To minimize interimplant bone resorption after prosthetic treatment and prevent a significantly greater degree of bone loss, the distance between two implants should be no less than 3 mm, and that between an implant and a natural tooth no less than 1.5 mm.65,176
Interdental papillae are present in 98% of cases if the distance between the Limbus alveolaris and the approximal contact point of the prosthesis is less than 5 mm. If the distance is increased to 6 to 7 mm, the stability of the papilla is reduced, and exists in 56% and 27% of cases, respectively.177
The formation of papillae between adjacent implants is more problematic. The size of interimplant papillae can only be predicted up to a distance of 3 mm between the alveolar bone and the contact point.53 A papilla can probably form between an implant and a tooth at a corresponding vertical distance of 4.5 mm.152,175
In the case of pontic solutions, however, papilla height is predictable at a distance of 5.5 to 6 mm between the alveolar bone and the contact point.152 These anatomical indices are considered indispensable, but they do not guarantee the formation of a papilla after surgical procedures.190
Soft tissue management is a very important factor in bone augmentation for the following reasons: 1) for the primary safety of the procedure; 2) for the esthetic result in the anterior area, since bony defects are also combined with poor soft tissue quality; 3) for function, reducing the muscle activity around the grafted bone and the implants; and 4) for the long-term stability of the definitive results. Primary, tension-free wound closure is indispensable in augmentation measures – bone grafts or guided tissue regeneration – and is a decisive prerequisite for the bacteria-free healing of the graft as well as for an eventually successful treatment. Gingiva quantity and quality are important factors, not only for good primary healing of the grafted bone to reduce the risk of tissue necrosis and graft exposure, but also for the long-term stability of the grafted area. In many cases, it is important to improve the quality and quantity of the soft tissue before a bone grafting procedure.
A periosteal incision in line with the Rehrmann technique increases the elasticity of the flap, so that its edges can be closed with external horizontal mattress sutures or simple interrupted sutures without tension in a two-layered procedure. The disadvantage of this procedure is the coronal adaptation of the mucogingival junction during augmentation and implantation, which has to be subsequently corrected for esthetic and functional reasons by a second or third implant-exposure procedure.97 Soft tissue management therefore plays a decisive role in restoring functional and esthetic soft tissue harmony.
3.1.1 Anatomy and vascularization of the soft tissue
An understanding of the macro- and micro-anatomical structure of periodontal and peri-implant tissue is a prerequisite for understanding the principles of plastic soft tissue surgery and exposure techniques. The different anatomical aspects are briefly presented and explained in the following sub-sections.
The gingiva consists of gingival connective tissue and overlying epithelium. With the exception of interdental cols, its surface is keratinized. The gingiva is located between the gingival margin and the mucogingival junction. The thickness of this layer is between 1 and 9 mm,23 with an average thickness of about 1 mm.52 It is thickest in the maxillary anterior region and thinnest in the mandibular lingual area.5 The width of the gingiva is significantly influenced by the position of the teeth,151 and changes with jaw growth.9 The orthodontic movement of the teeth in a bucco-oral direction can therefore correspondingly influence the gingival width.10
The keratinized, stratified, squamous epithelium reaches up to the cementoenamel junction and goes over into the sulcus epithelium to a physiologic depth of about 0.5 mm in the direction of the periodontal space. The oral sulcus epithelium is histologically similar to the gingival epithelium but is less parakeratinized. It is adjoined at the bottom of the sulcus by the marginal epithelium, with an epithelial attachment of 1 to 2 mm in width on the surface of the enamel. The marginal epithelium is stratified and non-keratinized and has a very high turnover rate.156 It is completely regenerated every 4 to 6 days by proliferating cell layers. If the marginal epithelia of adjacent teeth or implants adjoin, a non-keratinized col of a papilla is formed.81 This takes on a saddle-like shape in the interdental area and is dependent on the shape and dimensions of the approximal contact point. The function of the marginal epithelium is to protect the underlying bone from penetrating micro-organisms. This contact and reaction zone ensures that the organism performs immunologic engagement with chemotaxis and humoral defense away from the bones.
This attached gingiva reaching up to the mucogingival junction does not shift relative to the alveolar process, and the connective tissue matrix consists of collagen fibers to about 60%. It forms the supra-alveolar and supracrestal fiber apparatus of the tooth or implant. The collagen fibers are attached to the teeth in three-dimensional (3D) structures. They have a stabilizing function as regards the position of the teeth, and act as a functional unit of the periodontium in the root cementum and the alveolar bone.66
18.104.22.168 Peri-implant mucosa
The size, shape, and anatomy of the peri-implant soft tissue depends on wound healing determined by the position of the implant and by the implant system and exposure techniques used. It is comparable to the clinical characteristics of soft tissue around natural teeth.18,112,155
It has to be taken into account that instead of a periodontal ligament with physiologic mobility in relation to the anchorage, the implant has an osseointegrative connection with the alveolar bone. As a result, the peri-implant connective tissue fibers around the abutment or the surface of the implant are arranged in a parallel position in the supracrestal area, as opposed to being anchored to the dental root cementum.1,2,17,18 Peri-implant connective tissue also has a higher ratio of collagen fibers and a lower ratio of fibroblasts, and as such is very similar to scar tissue in histomorphologic terms.124,157
While the vascular supply of the gingiva is secured from the three anastomosing areas of the interdental septa, the periodontal ligament, and the oral mucosa, peri-implant connective tissue shows a relatively low level of vascularization. As a result of osseointegration, the vessels from the periodontal ligament no longer exist, which means that the vascular supply of the peri-implant mucosa is almost exclusively ensured through supraperiosteal vessels and a small number of vessels emerging from the bone.19 External bone surfaces are covered by a thin, inelastic layer of connective tissue that is rich in collagen – the so-called ‘periosteum.’ In addition to osteoblasts, osteoclasts, and the corresponding precursor cells, the periosteum also contains a large number of blood vessels and nerves, which are of particular significance for the regeneration of the freshly augmented bone, and may only be separated during exposure measures above the implant cover screws with the greatest possible care as regards the insertion of the gingiva former.
In particular, during surgical soft tissue management around implants, the scarred histomorphometry of the implant, the lack of anchored fibers, and the comparatively poor vascularization of peri-implant mucosa should in consequence be taken into account. Based on these differences, a reduced resistance to mechanical and microbiologic impacts as well as a compromised healing potential after surgical interventions can be expected due to the poorer vascular supply.116
22.214.171.124 Biologic width
The special structure of the gingival tissue around teeth and implants is a unique anatomical situation, where epithelial integrity is interrupted. This involves the formation of a combination of epithelial attachment against microbiological impacts and a connective tissue attachment against mechanical impacts, which is referred to as biologic width.84
Around teeth, the biologic width has a vertical dimension of 2.04 mm, of which an average of 1.07 mm consists of connective tissue attachment and 0.97 mm of epithelial attachment.66 Following exposure, a biologic width also forms around implants. The connective tissue attachment around implants is very constant compared with that of teeth, and has a width of about 1 mm, while the epithelial attachment – also called the long marginal epithelium – is significantly wider.157 The long marginal epithelium forms a connection to the implant or the abutment surface through hemidesmosomes and internal basal lamina.
Animal experiments have shown that, independent of closed or open healing, a small degree of vertical bone loss can be expected around implants, at an average of 1.1 to 1.3 mm apical to the implant–abutment junction.54–56 A coronal plaque-related and connection-related inflammatory infiltrate was discovered in the microgap between the abutment and the implant. Despite the topographic proximity of the crestal bone, a physiologic band of connective tissue has always been found. This band shields the bone from the 3D inflammatory infiltrate.54,55 However, vertical bone loss is still to be expected, in particular in the case of two-part implant systems. It reaches to about 2 mm apical to the junction,75–77 whereas the material of the abutment also has an influence on the transmucosal soft tissue.158
Independent of the design of implants, it has therefore been recommended that peri-implant soft tissue should have a thickness of at least 2 to 3 mm following exposure measures, in the interest of protective immune reactions. Also, a response of the organism can be expected in cases of increased peri-implant bone loss.30,39
The goal of placing gingiva formers or abutments during exposure surgery is to change the horizontal dimension of biologic width in line with the platform-switching principle, and thereby ensure the preservation of the periimplant bone tissue.36,110 Bone preservation should be further enhanced by replacing gingiva formers and abutments as infrequently as possible, with the least possible trauma to transmucosal soft tissue.1 Biologic width should therefore always be taken into consideration, also in relation to implants. Without hard tissue support, damage to the biologic width would become visible in the long run and would result in undesirable esthetic phenomena such as recessions and papillae losses.
126.96.36.199 Tissue biotype
From a clinical point of view, periodontal tissue biotypes can be classified in terms of form, profile, and thickness. Normal, thick, and thin biotypes are distinguished.161 Thick biotypes have a flat bone and gingiva profile with a significant width of keratinized gingiva. Rectangular and quadratic tooth forms co-occur here, and there is a correlation with thicker buccal alveolar walls.169 For this reason, bone dehiscence or fenestration is less frequently observed with thick biotypes. Thin biotypes can be identified on the basis of a steeper, garland-like gingiva profile, with a tendency for triangular tooth forms and a smaller width of keratinized gingiva. Patients with a thinner biotype are classified as high-risk because they have a significantly greater risk of developing not only buccal but also approximal recessions such as locus minoris resistentiae, which can be the result of multiple causes (i.e. trauma).61,185 Thin biotypes can be converted into thick ones with augmentative techniques, and the related risks can be minimized.
A direct measurement of the tissue biotype and its thickness can be performed by way of a clinical test based on the ‘transparency of the periodontal probe.’49
188.8.131.52 Attached and keratinized tissue
The formation of keratinized gingiva around teeth is considered a biologic development process due to the genetic determination of basal lamina and is therefore always present, at least in a minimal form. However, this phenomenon has to be created in peri-implant tissue using appropriate exposure techniques.
Since Lang and Loe106 proved in 1972 that teeth show more significant inflammatory phenomena if the width of the keratinized gingiva is less than 2 mm, this threshold has been regarded as an adequate size for maintaining periodontal health. Wennström and Lindhe183,184 proved in animal experiments that the size and apical dimension of the inflammatory infiltrate and the incidence of periodontal attachment losses do not differ between patients with an adequate width of keratinized gingiva and those with an inadequate width. A systematic review found that the amount of plaque accumulation, mucosal inflammation, recessions, and loss of attachment were more expressed to a statistically significant extent around implants where the width of keratinized mucosa was inadequate.115,148 However, it also has to be noted that an inadequate width of keratinized mucosa does not give rise to any noticeable negative effects on parameters such as BoP, probing depth, and radiographic bone loss.115 Despite the study by Keeve and Khoury94 referred to above, most scientific studies do not assess success criteria but implant survival rates, based on which it is still difficult to show whether attached mucosa results in any improvement. The present authors strongly recommend the restoration of attached mucosa as an important objective of exposure techniques. The keratinization of tissue and the resulting protective effect – also against the formation of recessions – is indispensable, in particular for esthetic reasons and for the preservation of a pale pink, dimpled, and keratinized surface around implants that is free of inflammation, i.e. appealing ‘pink esthetics.’
3.2 The basics of incisions, suturing techniques, and soft tissue healing
The aim of soft tissue healing is a good esthetic and functional final result, which includes complete morphofunctional restoration modeled on original structures. The incision, the formation of the flap, wound margin management, and suturing techniques have to be carefully considered in order to optimize flap healing and transplant receptivity and reduce scarring, especially in the esthetic area.
Principally, there are intraorally – and depending on the indication – two flap designs:
Incisions and flap design for bone augmentation and implant insertion must respect the general rules of surgery:
Two wound-healing processes are distinguished in the context of exposure measures. In the case of primary wound healing (per primam intentionem), the wound margins should be correctly repositioned throughout, which results in the direct closure of the superficial wound layers through the formation of a fibrin network, with optimal fibrinogen synthesis and neoangiogenesis. The tensile strength of the tissue is, however, only restored after the complete healing of the submucosa after about 1 to 3 weeks. In contrast, submucosal granulation tissue grows over tissue continuity defects in the case of secondary wound healing (per secundam intentionem), which is determined by neutrophil polymorphonuclear leukocytes and macrophages until the final epithelialization of the wound.
3.2.1 Cellular and molecular healing mechanisms
Wound healing involves both the repair and the regeneration of the damaged tissue. The inflammatory healing process mainly consists of reepithelialization, neoangiogenesis, and the activation of connective tissue cells, which also gives rise to the degradation of the proteins in the extracellular matrix and their resynthesis.159 The regulation of these processes is determined by interactions between proteins of the matrix and epithelial cells as well as cytokines and growth factors. After these three wound-healing phases are complete, the result is either an area of scar tissue formed by repair healing or an area of exact regeneration by original morphologically functional tissue.
184.108.40.206 Inflammation phase (day 0 to 3)
A brief vasoconstriction and the formation of the blood clot from a plasmatic network of thrombocytes and erythrocytes is followed by increased vascular permeability and the release of cytokines. The fibrinogen synthesis in the blood clot polymerizes fibrin and stimulates the migration and proliferation of marginal epithelial cells. Thrombocytes also release chemotactic cytokines such as TNF-α and IL-1 for neutrophil granulocytes and macrophages.79 This immune response decontaminates the wound by way of phagocytosis, cell-mediated immune response, and peroxides, before lymphocyte-recruiting macrophages enter the tissue. The lymphocytic reaction follows antigen presentation specific to the molecular patterns of various microorganisms.
220.127.116.11 Proliferative and fibroblastic phase (day 3 to 12)
The proliferation and migration activity of fibroblasts is enhanced by growth factors expressed by macrophages and leads to increased collagen synthesis and to neoangiogenesis triggered by VEGF and β-FGF.168 The reepithelialization of the wound margins restores the integrity of the anatomical structures. Integrins function as receptors for chemotactic factors, which interact with collagen and fibronectin, and PDGF of thrombocytes and TGF- of macrophages activate mesenchymal cells and thereby the formation of granulation tissue.44,79 Glycosaminoglycans, proteoglycans, tenascin, and thrombospondin invade the extracellular matrix, and myofibroblasts differentiate to contract the wound area.
18.104.22.168 Maturation phase (day 6 to 14)
Matrix metalloproteinases trigger collagenolysis and synthesis in order to reorganize the extracellular matrix and granulation tissue. The fibroblastic phase is determined by the formation of type III and I collagen and improves the tensile strength and elasticity of the new tissue. Integrins in the cell membranes consolidate the provisional matrix through α- and β-heterodimer proteins and enable reepithelialization. Integrin α5β1 not only stimulates adhesion and migration in this process, but also has a decisive effect on cell growth through signaling.12,86,109
3.2.2 The reactions of tissue to sutures
Suture materials are a foreign body and inevitably lead to mild inflammatory reactions in tissue, which may locally reduce resistance to infections. Specifically, needle and thread penetration sites represent biologic niches where bacterial invasions are possible.6
Wound healing in the oral cavity involves a higher risk of bacterial contamination, the so-called ‘wick effect.’ Biofilm formation therefore needs to be reduced as much as possible by using monofilament threads. Suture materials must possess high tensile strength and tear resistance, good knotting characteristics, and high knot strength.174 In this context, it was shown that atraumatic microsurgical application significantly supports flap and wound healing.25 The use of atraumatic monofilament suture threads with a maximum thickness of 0.01 mm (i.e. ≤ 6-0) is therefore indicated due to lower levels of bacterial colonization,114 smaller histologic inflammatory infiltrate, and the reduced formation of scar tissue. At the time of the removal of the sutures after 14 days, the epithelium is already keratinized,159 and the thread is slightly colonized by rod- and spindle-shaped bacteria. Due to the complex, multilevel suturing techniques used to achieve esthetic and functional results, it is recommended to use resorbable suture threads. Nevertheless, as the metabolic degradation process takes approximately 60 days, these should be removed if accessible after 14 days. This results in greater patient comfort and is obligatory in the particular case of two-layer wound closure. The surgical needle should have a curve length of 11 to 13 mm, and a triangular profile sharpened and polished toward the tip. The needle should be made of stainless steel to achieve the best possible stability while causing the least possible trauma to the tissue (Fig 3-2a to d).
Microsurgical concepts have become established in soft tissue management.46,189 Microsurgery is understood to mean surgical procedures that require optical magnification aids, miniaturized instruments, and suturing materials that have been adapted accordingly. The atraumatic management of tissue and the optimal closure of wounds by way of microsurgical techniques have produced significantly improved results. The improved and predictable wound healing process was described by Burkhardt and Lang,25 who compared macrosurgical and microsurgical procedures.
The shape of the instruments’ grip should be round and well-balanced and have a length of at least 16 cm. In particular, in the case of lengthier procedures, such ergonomic work in the posterior sections of the jaw may have advantages. Grips with a round profile make possible the significantly more precise manipulation of instruments in the pencil-grip position.
On the one hand, an incision without any tissue loss is possible with a single-edged No. 15c blade with a pointed tip and adequate width in the case of two-layer dissections; on the other hand, one could use a double-edged SM69 micro scalpel. In the selection of raspatories (e.g. Partsch Raspatories), a slender design is best. Larger raspatories can only be used for the atraumatic lifting of flaps. There should be at least one anatomical and one surgical forceps, the latter specifically designed for microsurgery. Without lip and muscle retraction, a delicate flap, or a free or pedicle connective tissue graft, can be optimally held using a surgical Cooley forceps without much pressure. If too much pressure is applied in the case of anatomical forceps, the delicate flap can be significantly traumatized or bruised. In the case of very thin flaps or free mucosal grafts, an anatomical forceps is the best choice for atraumatic handling without the risk of perforation. For knotting suture threads, either an anatomical or a surgical forceps with plateau is suitable to avoid any damage to the suture materials when grabbing them. As regards the choice of needle holder, in addition to the needle size to be used, the level of experience and the preference of the surgeon play a decisive role. Various sizes of the required shape as well as a slender design are needed to ensure appropriate access to the interdental areas. Microsurgical needle holders are usually not equipped with a lock, although it is of great help in oral and periodontal surgery for controlled rotating movements. The needle holder by Castroviejo is, for example, equipped with a gentle locking mechanism. In the case of micro scissors, curved shapes with pointed blades have proven to be practical.
3.4 Soft tissue management before augmentation
Inflammatory processes and tooth extractions sometimes lead to pronounced damage to both hard and soft tissue. In particular, the quantity and quality of soft tissue, including its regenerative characteristics, are severely compromised in cases involving infected biomaterials or failed implantation attempts with multiple previous surgeries. It can be an advantage in all these situations to improve the quality of soft tissue in this region before actual augmentative measures. This allows for an easier and safer closure, primarily in relation to vertical bone augmentations. Soft tissue improvement is most frequently indicated in patients with a thin gingival biotype, as the improved soft tissue has a protective effect on the hard tissue graft and ensures a better long-term esthetic result.
A thin biotype is easily diagnosed by probing, as the periodontal probe is visible through the tissue, and it is a predisposing factor for the formation of recessions. It may therefore be reasonable to change biotypes from thin to thick, with consideration of esthetics. This can be achieved by both free gingival and connective tissue grafts and palatal pedicle connective tissue flaps (Fig 3-4a to l). Rotation flaps can be created, epithelialized or deepithelialized from buccal mucosa or the palate. The volume and quality of the soft tissue can also be improved through free gingival and/or connective tissue grafts, which can at the same time counteract shifts in the mucogingival junction.
3.4.1 Incisions before augmentation
From the very beginning, the adequacy of the cuts has great significance for the later esthetic success. If the existing tissue is thin, it is recommended to place the incision strictly vertically in order to achieve two equally thick flap margins and thereby optimize suture closure, healing, and the final results. Independent of the phase of soft tissue management, the incision should ensure the necessary accessibility of the operation site and offer the required mobilization opportunities. In the case of sulcular incisions, the blade cuts papillae directly under the tooth contact point, parallel to the tooth axis, and the whole gingiva is incorporated into the flap. Releasing incisions in the gingival margin should be altogether avoided before augmentation; the only exception is in the case of auxiliary access incisions in the mucosa for the placement of grafts. In the pre-augmentative phase, only mucosal flaps – also called split-thickness flaps – should be used (Fig 3-5a to o). If a thin layer of connective tissue and periosteum are left on the bone, grafts heal better due to the vascular supply from all sides.134 In addition, the resulting bone resorption can be minimized in the case of a split-thickness flap dissection, as compared with mucoperiosteal flaps with denudation of bone.60,135,166,187 Exceptions to this concept are situations where the soft tissue augmentation has to be combined with the removal of foreign materials (e.g. biomaterials after infection). In such cases, the flap preparation must include bone exposure to remove the foreign materials.
3.4.2 The split-thickness tunnel technique
Soft tissue thickening is mostly achieved with connective tissue grafts. The split-thickness tunnel technique involves the use of free grafts that restore volume, in particular on the vestibular aspect of the defect, and therefore completely exclude the risk of exposure during later augmentation measures. After the free connective tissue graft is harvested from the palate, the graft bed is opened – beginning with a vertical mucosal incision – and a Partsch Raspatory or Kornman scissors are used to bluntly dissect a tunnel toward the target site. The tunnel is created to be 1.5 times the size of the excised graft, preserving the anatomical structures as much as possible (Fig 3-6a to e). The tunnel is centered on soft tissue deficits and reaches the keratinized areas of the gingiva, if necessary. If the keratinized gingiva is very thin, a transition into a mucoperiosteal flap at the mucogingival junction may be necessary to avoid perforations. The graft is pulled in using a sling suture at the distal end of the tunnel, which can then be knotted in the same step to a mattress suture. The graft should be fixed in the correct position by at least two mattress sutures, with the use of a few simple interrupted sutures to prevent rotation before the vertical access incision can be closed (Fig 3-7a to l).
3.4.3 Free connective tissue grafts before augmentation
Connective tissue grafts are primarily harvested from the lateral palate, independently of the phase of soft tissue management. Further donor sites include the tuber maxillae and the mandibular retromolar region. Free tissue grafts can be categorized into connective tissue grafts, gingival grafts, and grafts, the last being a combination of the first two. The ‘lateral palate’ donor site should, however, be further specified, as the tissue is thickest in the premolar region of the palate. Depending on the patient, subepithelial tissue grafts also include fatty and glandular tissue, in addition to collagenous areas (Figs 3-5c and 3-7d). The palatine artery is to be preserved; it emerges from the foramen palatinus major at the approximal space of the second and third molars,101 and continues anteriorly at an average distance of 12 to 14 mm from the gingival margin,123 depending on the height of the palatal vault.142 The so-called ‘single-incision technique’ has been preferred in many described harvesting techniques used to dissect subepithelial grafts,83,107 as it has been found to improve postoperative healing and patient morbidity. The technique involves a horizontal incision on the palatal side, followed by a sharp undermining dissection. The wound margins can be optimally stabilized during later suturing if the harvesting incision is 1 to 1.5 mm from the first incision. Depending on the patient, a decision needs to be made as to whether the graft should be elevated from the bone bluntly or by using a further split-flap dissection. The blunt approach enables the excision of a more voluminous and more stable graft, incorporating the periosteum but at the price of slightly greater patient morbidity. For suture care, a combination of continuous sling sutures, simple interrupted sutures, and a palate plate is recommended (Fig 3-7e).
If connective tissue with a higher ratio of collagen and less fatty and glandular tissue is required, a deepithelialized gingival/connective tissue graft is recommended. Alternatively, the tuberosity region is recommended as a secondary donor site. Grafts gained using a distal wedge excision will shrink less due to their structure, and have a special form, which makes revascularization difficult. For this reason, the tuberosity region remains the secondary donor site.
In addition to own tissue-specific proteins, autologous connective tissue grafts also contain a significant number of fibroblasts, the majority of which are accessible for initial plasmatic circulation and the revascularization that follows, for which reason they have a more favorable prognosis.
3.4.4 Punch technique
If there are no acute inflammatory symptoms, the so-called ‘punch technique’90 – involving a combined graft consisting of connective tissue and epithelial parts – can also be used for the closure of extraction or explantation alveoli. This technique results in an optimal stability of the coagulum in the alveolus, and it compensates for the volume and keratinization of the soft tissue. The graft can be harvested from the tubera behind the last molar in cases where there is a wide keratinized gingiva in this area (Fig 3-8a to j) or from the palate in the premolar area. In the case of the palate, a rotated punch bur can be used to facilitate the harvesting procedure (Fig 3-9a to l). In the case of the graft being harvested from the tubera, an incision is made in the middle of the connective tissue area that will create two strips of connective tissue by keeping a central epithelial area, with a diameter corresponding to that of the extraction socket. Split-thickness flaps are dissected without incisions in the area of the alveolus on both the buccal and oral sides using the tunnel technique. The size should be double that of the connective tissue strips, which can be fixed buccally and orally with two sling sutures. For final wound care, the epithelial area of the graft is adapted to the surrounding epithelium. As a result, the areas covered with epithelium are not covered with an auxiliary flap and are therefore exposed in the oral cavity. The lobes gained, however, ensure the improved revascularization and diffusion of the graft and the additional increase in volume in the bucco-crestal region.
Damage to bone but also to soft tissue can be so severe after the extraction of a tooth or the explantation of an implant, particularly in the case of failed augmentation procedures, that closure using the punch technique is no longer adequate to ensure the required volume. In such cases, coverage of the extraction socket can also be safely achieved after immediate implantation with a palatal pedicle connective tissue flap. The existing soft tissue deficit can be evened out and covered by creating a mucoperiosteal flap using the Rehrmann technique163 or by a connective tissue graft.35 The use of palatal pedicle connective tissue flaps is of course limited to the maxilla for anatomical reasons. A pedicle graft from the palate, which at least retains a minimal vascular supply, has a better prognosis in areas previously operated on multiple times with an accordingly degraded recipient bed, and leads to safer coverage than free grafts without any arterial vascular connections. Grafts of a thickness of 2 to 5 mm or thicker96,170 rotated from the palate can be mobilized in almost any desired maxillary region, depending on the pedicle. Rotating palatal flaps can be characterized as epithelialized or non-epithelialized, and as having an anterior or posterior pedicle.96
Originally intended for ovate pontics,182 the palatal flap described by Khoury and Happe96 was published as a technique for covering augmentative measures involving soft tissue augmentation and possible wound closure following immediate implantation.90 By applying the single-incision technique, total rotation can be achieved by starting with a long, straight, horizontal incision at a distance of 2 to 3 mm apical of the gingival margin, with its described advantages.50,83,108 In this context, it was shown that the narrow base of the pedicle flap ensures blood flow within the graft and therefore also promotes healing that is more independent of the recipient site.96 In an ideal case, the length of the flap should not exceed 2.5 times the width of the flap base and should be fixed in the recipient bed without tension.47 The width of the graft depends on the height of the palate and lies within a range of 7 to 17 mm, according to scientific studies.141,142 In the case of undermining dissection, the connective tissue is separated from the overlying mucosa, as in the case of free connective tissue grafts. The remaining epithelial top layer should not be thinner than 1 to 1.5 mm. If this thickness is not achieved, the risk of donor site necrosis, delayed healing, and greater resulting patient morbidity increases. If the length and depth of the graft is sufficient, the periosteum is dissected at the apical and – depending on the pedicle – distal side, and is elevated using a raspatory with consideration of the mesial vascular pedicle. The periosteum should also be elevated with the flap, as it will be fixed on the alveolus when it is covered or when indicated by the stage of bone augmentation. This periosteal cover ensures a stable flap and the alignment of anatomical structures corresponding to the original (Fig 3-10a to v).
As an alternative, first a palatal mucoperiosteal flap may be formed, which is dissected into a connective tissue layer (graft) and an epithelial layer following elevation. The rotation of the palatal flap and its connection to the receiving site can be performed either by using a horizontal palatal incision between the donor and the recipient bed, or by using a tunnel and keeping a mucoperiosteal soft tissue bridge between the regions (modification according to Dr Alain Romanos, Beirut, personal communication). The first option allows for a good view and more length and volume of the connective tissue, the second for completely intact anterior palatal tissue in the region of the recipient bed, with all the advantages of better vascularization and healing of the graft (Fig 3-11a to e).
When closing an alveolus, the undermining dissection of the split flap may be performed buccally, which allows for the graft to be pulled into and fixed in the tunnel that has thereby been created using a mattress suture, as with the punch technique. The complete coverage of the graft is not necessary, as even with free connective tissue grafts only about 90% of the area has to be covered for uncomplicated healing.188 The suture care of the donor site is identical with the approach described in relation to free connective tissue grafts, with the exception that a block-out is recommended in the palate plate in the area of the rotation site.
In some situations, the palatal pedicle connective tissue flap can be combined with an epithelial vestibular rotation flap: The connective tissue flap increases the soft tissue volume and the epithelial flap covers the connective tissue to ensure additional vascularization (Fig 3-12a to j).
3.5 Soft tissue management during augmentation and implantation
Primary wound closure plays a decisive role in the success of bone augmentation.105,136 Microsurgical procedures, precise incisions, flap elevations, and tension-free wound closure are considered essential for optimal results.26,47 The problem of incomplete wound closure can be solved with free or pedicle flaps. It is also important to keep flaps hydrated with moist gauze if the procedure is interrupted.
3.5.1 Incisions during augmentation and implantation
Every surgical procedure involves the formation of a full- or partial-thickness flap. Only the most necessary incisions should be made, regardless of whether they run horizontally or vertically. Implantation requires direct access to the bone surface to achieve a correct implant position. This access can be achieved either by crestal or horizontal incisions in the vestibule. The comparison of these two incision types did not show any difference in the survival rates of implants or their osseointegration,82,136,153 although vestibular incisions resulted in more significant scarring in the vestibule. From an anatomical point of view, vestibular and oral vascularization are divided precisely along the midcentral–crestal line of the alveolar process, and are only connected through a few anastomoses.100 For this reason, to achieve long-term success it is particularly important to ensure that the lingual attached gingiva is preserved in procedures on the mandible.115 Incisions are placed in a manner that ensures that suture closure is further away from the augmentation site. However, when pure autogenous bone is used, the risk of dehiscence or tissue necrosis is much less than when foreign materials are used as membranes or biomaterials. This is related to the primary biology of healing. When, after a surgery, the flap is repositioned and sutured in a tension-free manner, the only function of the sutures is to adapt the two wound borders together without attempting to hold the flap in this position for a longer time against the muscle activity. The flap is held in this position through adhesion to the underlying tissue, which functions correctly if the underlying tissue is autogenous. If the underlying surface is a biomaterial or a membrane, this adhesion will be difficult. For this reason, when biomaterials and membranes are used, the wound borders should be far away from the augmented area, and the tissue releasing should be much more intensive. In addition, the stability and number of sutures should compensate for the poor adhesion.
Releasing incisions are used to create trapezoid flaps with a wide base and therefore good vascularization while allowing the best possible view of the operation site. To prevent papillary necrosis or the formation of recessions, diagonal vertical incisions extended from the intrasulcular incision should not terminate either in the area of the tip of the papilla or in the area of the bottom of the vestibule of the gingival margin. More precisely, they should begin at the 1/3 or 2/3 position of the vestibular tooth perimeter and reach slightly beyond the mucogingival junction, as long incisions do not heal significantly less well than short ones.47,136 This allows for an optimal view of the operation site and minimizes tension on the tissue during the procedure. As the vascular supply of the maxilla and mandible runs in a posterior to anterior direction, every vertical relief incision needs to be very carefully considered and possibly avoided. A single vertical incision is often sufficient to allow for a view of the site. In particular in the anterior region of the maxilla, normally until the first premolar, the one releasing incision in the case of bone augmentation is placed on the gingival mesial third of the distal tooth for esthetic reasons. This kind of incision – after cutting the periosteum – makes the wound closure covering the augmented area easy, since the flap movement will be running in the same direction as the releasing incision (Fig 3-13a to m). If due to scar tissue it is not possible to obtain a hermetic closure with one vertical incision, there is always the possibility of performing a second vertical incision running in the mesial third of the distal tooth (Fig 3-14a to f).
In the posterior area of both the maxilla and the mandible, the one releasing incision is performed on the distal or mesial third of the mesial tooth (mesial releasing incision) because in this situation good visibility of the operation area is much more important than the esthetic risk (Fig 3-15a to c). In addition, a mesial releasing incision is the best option for avoiding a significant restriction of vascularization arising from the distal aspects.100,136 In a similar way to the anterior area, the surgery always starts with one releasing incision. If necessary, a second one is performed at the end of the procedure.
Moderate bone resorption processes occur in the case of periosteal elevations, which should be avoided as much as possible by keeping deperiostealization to the minimum.186 It is generally recommended to elevate a mucoperiosteal flap for the purposes of augmentations and implantations. In special cases, where there is an indication for bone-splitting methods or expansion procedures, a supraperiosteal flap for the apical component is potentially recommended to preserve nutrition through the periosteum (Fig 3-16a to c). A similar situation can occur if bone spitting is possible on one side of the surgical area while heavy grafting is indicated in another area. In this situation, there will be two different flap preparations: a partial-thickness flap, leaving the periosteum on the bone where the splitting will be performed, and a full-thickness flap where the bone augmentation is indicated (Fig 3-17a and b).
3.5.2 The tunnel technique
The most frequent complications following hard tissue augmentation are wound dehiscence with exposure and infection of the augmented bone.57 These complications occur more often in cases of vertical augmentation and/or in smokers.40,113 The tunnel technique has been developed to significantly reduce the risk of dehiscence or necrosis and thereby the risk of losing the graft. It involves making one or the maximum of two vertical incisions, so that the integrity of the crestal soft tissue (including the periosteum) is not affected, and vascular supply to the strategically important areas is preserved as much as possible.
Originally intended as a preprosthetic measure for the absolute heightening of the alveolar crest of the mandible,150 and also described as a means of extensive augmentation in the maxilla,88 Khoury modified this technique further as the best possible protection for autologous bone grafts in the healing phase.97,99 This procedure can be combined in the posterior maxilla with the augmentation of the sinus floor, leading to a double augmentation over and under the sinus crestal bone (Fig 3-18a to s). In the anterior maxilla, it is recommended to use such a technique in cases where at least two teeth are missing, in order to have enough tissue to cover the vertical augmented area (Fig 3-19a to n). Since the periosteum will still be intact and cover most of the grafted bone during such a procedure, the remodeling and resorption of the graft will still be limited, maintaining mostly its original volume, including after many years (Fig 3-20a to k).
This procedure is more difficult to perform in the posterior mandible due to the reduced visibility, the need to harvest bone from the same side, and the thin biotype of the crestal and lingual mucosa. Especially the presence of the thin biotype can increase the risk of lingual graft exposure if the occlusal thin bone block is placed more lingually. However, if this approach is performed correctly, it offers the excellent possibility of minimizing the risk of graft exposure in a very difficult area where many muscle activities take place (Fig 3-21a to v).
A vertical incision in close proximity to the recipient bed is made to dissect a tunneled mucoperiosteal flap using raspatories. The size of the mucoperiosteal flap should correspond to the full necessary mobilization height. Bone grafts can then be fixed with micro screws, not only for lateral but also for vertical 3D augmentation of the required shape. If there is an insufficient view of the site, an opportunity exists for a second vertical incision in the posterior area, which incorporates the thereby crestally created bridge flap as a tunnel and also offers the possibility of harvesting bone from the same side. A periosteal incision is then no longer necessary to achieve tension-free wound closure due to the particular dissection and size of the elevated tunnel. The result is that an intact periosteal layer is preserved on the graft, which ensures unobstructed vascularization (Fig 3-22a to p). This access method also significantly reduces the incidence of woundhealing disorders.137 Independent of the incision line, the flattening of the vestibule, in particular in the case of 3D augmentations, can be corrected in the mandible with the use of the Kazanjian vestibuloplasty during implantation64 (Fig 3-23a to i), and in the maxilla during exposure measures with an apically repositioned advanced flap.
In a 10-year clinical study conducted by Khoury and Hanser95 between 2003 and 2007, vertical bone augmentation was performed in the posterior maxilla on 142 consecutively treated patients with a total of 154 grafted sites using the tunnel approach. Autologous bone grafts were gained from the retromolar region using the micro saw technique. Minimal graft exposure (1 to 3 mm) 4 to 8 weeks postoperatively was documented in two sites. Infection of the grafted area occurred in one other case. The average preoperative clinical vertical defect was 7.8 ± 3.9 mm and 3.1 ± 2.2 mm of horizontal width. Postoperatively, the average of the vertical gained dimension was 7.6 ± 3.4 mm (maximum 13 mm) and 8.3 ± 1.8 mm in width. In all sites, implants could be inserted (a total of 356 implants). The amount of maximum vertical bone resorption after 1 year was 0.21 ± 0.18 mm, after 3 years 0.26 ± 0.21 mm, after 5 years 0.32 ± 0.19 mm, and after 10 years 0.63 ± 0.32 mm. Four implants were lost within 10 years. The average of vertically gained bone was stable at 6.82 ± 0.28 mm (maximum 12 mm). The resorption rate after 10 years was 8.3%.95
In conclusion, a correlation was found between opting against a crestal incision and the low incidence rate of wound dehiscence. The tunnel technique therefore offers improved predictability in particular in relation to vertical augmentation.95,137
3.5.3 The lateral tunnel technique (lateral approach)
The creation of a flap requires an incision line that does not cross the augmented area in the lateral mandible, and also requires that the lateral mandible can be covered with a thick layer of soft tissue with sufficient vascular supply. This helps to avoid the exposure of the bone, in particular in the case of vertical bone grafts.
The horizontal, slightly slanted incision27,28,89 is placed about 2 cm below the mucogingival junction, in the buccal mucosa, in the length of the edentulous section. This position of the horizontal incision can also be individually measured, depending on the amount of the planned vertical augmentation: If, for example, a vertical augmentation of 7 mm and a horizontal augmentation of 8 mm are planned, in order to cover the graft correctly the position of the incision measured from the middle of the crest should be: 7 + 8 = 15 mm + 5 mm security = 20 mm. Vertical incisions should be avoided, if possible, to preserve vascular supply. As this incision is performed in well-vascularized tissue, heavy bleeding must be expected after the preparation of the partial-thickness flap, including the mucosa and part of the muscle. To prevent such bleeding, it is recommended to inject a sufficient volume of local anesthesia with vasoconstrictor about 15 min before the surgery. The slightly slanted initial incision offers a larger attachment surface for the tension-free closure of the wound. During the following supraperiosteal dissection toward the mucogingival junction and to preserve the mental nerve, a thick lingually pedicled flap is formed, which is dissected as a mucoperiosteal flap over the alveolar crest shortly before the mucogingival junctions are reached following the periosteal incision. The periosteal flap, which is still attached on the vestibular side, can now be elevated. After the completion of the augmentation and/or implantation, the periosteal flap is sutured to its lingual stem on the inner side of the flap, i.e. the area of transition from a mucosal flap to a mucoperiosteal flap. Using two-layered sutures, the muscle insertions are realigned and the mucosal component at the end is closed (Fig 3-24a to q).
3.5.4 The Kazanjian vestibuloplasty
The loss of teeth in the mandible not only leads to the atrophy of the alveolar process but also to the reduction of keratinized attached gingiva.37 In addition, augmentative measures aimed at restoring the alveolar bone usually have the temporary effect of the mucogingival junction shifting coronally and the vestibule becoming flatter. Systematic reviews have found that attached mucosa around implants plays a decisive role in the long-term preservation of the implants.94,115 As opposed to the maxilla, where there is a sufficient amount of keratinized mucosa to be used in reposition flap procedures, the options for restoring attached mucosa in the mandible are limited. The Kazanjian vestibuloplasty is one of the options for the creation of a wide band of attached mucosa and for the reconstruction of the vestibule (Fig 3-25a to f). It was originally developed for the preprosthetic deepening of the vestibule, and its use is indicated in implant procedures for the creation of attached, but not keratinized, mucosa.93,118 One of the significant advantages of this vestibuloplasty is the opportunity to perform implantation, augmentation, and soft tissue management in a single procedure, so that extensive exposure measures are no longer needed.
An initial horizontal, superficial incision is made about 2 cm below the mucogingival junction in the length of the edentulous section, and only the mucosal and submucosal layers are later elevated with the flap. Two vertical incisions run from the end points of the horizontal incision over the alveolar crest up to the lingual junction of keratinized mucosa, where coronal to the mucogingival junction the incision should become mucoperiosteal. In the next step, a strictly supramuscular flap of a thickness of at least 1.5 mm is dissected toward the mucogingival junction. Upon reaching this anatomical structure, the periosteum has to be dissected with a horizontal incision in order for it to then continue with the elevation of a mucoperiosteal flap in a coronolingual direction. The following step is the sharp dissection of the muscle insertion from the periosteum about 2.5 cm toward the vestibule while preserving the mental nerve. Depending on the bone defect, the remaining periosteal flap on the vestibular side can be elevated for exposing the bone for implantation. After the augmentation and/or implantation is completed, the periosteal flap is sutured to its lingual stem on the inner side of the flap, i.e. the area of transition from a mucosal flap to a mucoperiosteal flap. After the sharp detachment of the muscle insertion, it is now possible to fix the mucosal component of the lingual flap to the periosteal flap in the new vestibule using simple interrupted sutures. The muscle insertion is, of course, left to heal by secondary healing and cannot form a reattachment due to the adaptation of the mucosal flap as a barrier (Fig 3-26a to k).
In the case of the augmentation of larger bony areas, the attachment of the periosteal flap to the mucosal–mucoperiosteal flap usually represents a challenge. This can be simply resolved in the anterior and molar regions by a periosteal incision below the apical dissection point of the muscle. In the anatomical and topographic proximity of the mental nerve, it is essential to avoid such a deep periosteal incision; however, the gap between the reattached periosteal components can be covered using the two-layered wound closure technique described above (Fig 3-27a to f).
In comparison with other vestibuloplasty techniques, such as that described by Edlan and Mejchar, Kazanjian’s technique has the advantage of a significantly lower degree of bone exposure, also in the healing phase, and therefore also reduces postoperative bone resorption and patient morbidity.64,119,167 The advantage of both vestibuloplasties is the retraction of the muscle insertion, which affects both the function and the esthetics of the soft tissue interface.103 However, such an extensive intervention in the vestibule is indispensable, as within a period of 36 months the rate of recurrence is higher than in the case of vestibuloplasties according to the Edlan-Mejchar method. Based on a 6-month follow-up period, a stable, surgically increased vestibule depth can be achieved in 80% of Kazanjian’s vestibuloplasty cases.103
3.5.5 Free connective tissue grafts during augmentation and implantation
The atrophy of the alveolar process following the loss of teeth involves the loss of both hard and soft tissue, particularly in cases of previous inflammation. To restore the original conditions, it is recommended to enhance the volume and quality of soft tissue with a connective tissue graft at the time of the bone augmentation measures. This involves the placement of an avascular, free connective tissue graft onto a bone graft without or with only a low level of vascularization. As the vascular supply of the graft is severely limited, the survival of a free soft tissue graft over a bone graft will be difficult, and will lead to total or partial necrosis and volume retraction.96,97 This problem can be better counteracted during implant placement after the grafted bone has healed, with the preparation of a two-layer flap and the formation of a pocket for the graft. First, the bone augmentation site is closed using periosteal tissue. Then, a connective tissue graft is fixed supraperiosteally with mesial and distal sutures. In the third step, the mucosal flap is closed primarily over the layers. A two-layered closure is indicated with a view to plasmatic diffusion and healing processes in the early phase of healing. This significantly increases the likelihood of early revascularization, resulting in the preservation of the created volume (Figs 3-28a to k and 3-29a to j).
The preparation of a vestibular periosteum flap during implantation to cover the inserted implants and to support the connective tissue grafting is not always easy. An alternative is to increase the soft tissue volume and to correct some soft tissue problems. For instance, recession on the neighboring teeth can be corrected by grafting the connective tissue shortly before implant exposure. This will guarantee good healing of the free graft because the graft will be totally covered (Fig 3-30a to f). In case of soft tissue augmentation during bone augmentation, it is more secure to use the pedicle alternative of the connective tissue graft (see Chapter 4).
3.5.6 Palatal pedicle connective tissue flaps
This procedure corresponds to the one described in the previous section. In this phase, however, the following should be taken into account at the end of the intervention:
The palatal flap is fixed to the base of the buccal flap – or if a periosteal incision is necessary, the apical component of the buccal periosteum – with resorbable sutures. The buccal flap is then closed over the graft with the corresponding palatal flap with horizontal mattress and simple interrupted sutures.
The combination of a pedicle flap with bone augmentation offers two significant advantages. First, it is possible to achieve two-layered wound closure and therefore optimal protection of the bone graft from dehiscence, exposure, and infection. Second, soft tissue coverage is ensured for future esthetic results (Fig 3-31a to j). For this reason, palatal flaps are very often used in the maxillary anterior region. These flaps are used to achieve better protection of the grafted area through the advantage of a two-layer closure, for soft tissue socket coverage after immediate implantation (Fig 3-32a to e), for soft tissue augmentation for various reasons, for the coverage of recessions on teeth and on implants, and for papillae reconstruction techniques.
In cases involving the maxillary first incisor, harvesting the graft from the contralateral side may be considered to preserve the ipsilateral vascularization from the palate to the augmentation site. Another alternative in the maxillary anterior area is the modification of the palatal pedicle flap by leaving a small soft tissue bridge, offering advantages for better flap adaptation and simultaneously reducing the risk of flap necrosis (Fig 3-33a to f).
The use of pedicle grafts in the distal region of the maxilla corresponds to the description above, with the single difference being that the vascular pedicle does not remain in the anterior but in the posterior palatal area. The main indication for such a procedure is the protection of vertical grafted bone through a two-layer closure (Fig 3-34a to m). Another indication is the closure of a mouth–antrum connection.
3.5.7 Vestibular pedicle connective tissue flap
Increasing the volume of crestal and vestibular mucosa through a palatal pedicle connective tissue flap before the bone augmentation offers the possibility of a two-layer closure though the preparation of a vestibular pedicle connective tissue flap. This alternative to the palatal connective tissue flap during bone augmentation reduces the risk of necrosis of the crestal/palatal mucosa and exposure of the grafted bone in the anterior maxilla, since the preparation of a palatal pedicle connective tissue flap reduces the vascular supply of the palatal mucosa.
The technique from the surgical point of view is sensible: A horizontal incision is performed deep in the vestibule, including the periosteum and part of the connective tissue, to a depth of about 2 to 3 mm. This incision is followed by flap preparation, with the width of the bone grafted area and in the crestal direction. This periosteum/connective tissue flap is designed to have a large pedicle with a height of about 5 mm on the crestal top of the original mucoperiosteal flap. Care should be taken to obtain a good mobile connective tissue flap but without perforation of the vestibular flap, i.e. the pedicle should not be reduced to less than 5 mm in height, nor should it be completely cut. This flap is than pushed under the palatal periosteum, where it is fixed with resorbable sutures covering the grafted bone as a first layer. The second layer is then performed with the vestibular flap (Fig 3-35a to z).
Pedicle periosteal flaps can be used in all areas of the maxilla or mandible where there is a need for two-layer closure. The indications for such flaps include the presence of a thin gingival biotype or thin mucosa in the area of the bone augmentation, as a result of which pedicled grafts cannot be rotated from the palate to the site of the two-layered wound closure. In such situations, it is recommended that a pedicle periosteal or periosteal muscle flap be prepared from adjacent flap components and be fixed onto the graft. The mucoperiosteal flap is then reflected on the first layer and is fixed, as in two-layered wound closure. In the maxilla, such periosteal flaps are usually dissected with an anastomotic link from the distal area of the wound, while preserving important anatomical structures such as the terminal branches of the infraorbital nerve and the excretory duct of the parotid gland. In the mandible, the principle described above involving a periosteal flap from the distal areas of the wound is applied, while preserving the terminal branches of the mental nerve, and in the molar region, the facial artery. One of the main indications for such a procedure is the covering of a membrane with a two-layer closure to prevent the early exposure of the membrane (Fig 3-36a to e). Since the periosteum is relatively thin in the posterior mandible, the preparation of such a flap occurs distally of the mental nerve and, in addition, includes parts of the masseter muscle that will be rotated mesially to cover the grafted area in a first layer (Fig 3-37a to h).
3.6 Soft tissue management during implant exposure
3.6.1 Incisions for implant exposure
The preservation of volume and the shaping and keratinization of tissues have particular significance in relation to exposure techniques.15 It is important to meet all soft tissue criteria for optimal functional and esthetic long-term results of implant care in this phase of the therapy. However, implant exposure with the use of punches, electrosurgery or laser is obsolete because, despite the admittedly simple and fast procedure, important soft tissue is destroyed.22,78,97,114 This soft tissue loss mostly occurs in the area of keratinized and attached mucosa (Fig 3-38). For this reason, if used at all, exposure by way of an excision should be restricted to situations where the gingiva is sufficiently wide, attached and keratinized.
3.6.2 Displacement during implant exposure
If the attached and dimensioned mucosa is of a sufficient width, it is indicated that the implant should be exposed by displacing the covering soft tissue.78 This technique is more often used in the mandible, as here adequately dimensioned and attached mucosa is usually already created by way of a vestibuloplasty during augmentation and implantation. Displacement is a fast and efficient procedure that only involves moving a small amount of tissue. As is favorable for the given deficit, the covering mucosa can be displaced in a buccolingual or mesiodistal direction. Displacement in a buccal or lingual direction is achieved with a mesiodistal incision, where the position of the incision is chosen to best benefit the tissue to be displaced. Displacement in a mesiodistal direction is similar, and requires a buccolingually oriented incision line for the creation of an adjacent papilla. It essentially leads to a slight ‘puffing up’ in the required region without any loss of keratinized or attached gingiva. If performed carefully, without traumatic tissue rupture or the exposure of the alveolar bone, no sutures are necessary for wound care. Releasing incisions are usually performed horizontally, as a continuation of the original incision. If the dilation of the incision is limited, the so-called ‘H incision’ may provide some help and a good view. This involves making two small vertical incisions at the ends of the initial one, so that the soft tissue can be better mobilized, e.g. around wider-diameter implants (Fig 3-39a to c).
In such a procedure, it is very important to move most of the keratinized gingiva to the lingual side (Fig 3-40a and b), even if this means more surgery (Fig 3-41a to h), since a lack of fixed mucosa lingually is difficult to correct later, which is not the case with missing fixed or keratinized gingiva on the vestibular side. In this situation, it is always possible to easily perform a vestibuloplasty with a soft tissue graft. Keratinized and fixed mucosa on the lingual side reduces the muscle activity on that side and is an important factor for long-term stability of the peri-implant soft tissue.
Displacement is a fast and simple method for the exposure of implants. However, corrections of the soft tissue are only possible to a very limited extent, and the poor view over the site can, at times, make it difficult to verify the correct insertion of the gingiva former.
3.6.3 The so-called ‘M incision’
A variant of displacement is the M incision, which involves the displacement of the mucosa covering the implant to the approximal spaces. The incision line is chosen so that the base of the M shape is positioned buccally, while the tips are positioned orally. The lower part is then displaced to the buccal edge of the implant, while the V-shaped middle is parted in two with an incision and is sutured to the tips of the M incision on the mesial and distal side of the implant (Fig 3-42a to c).
In addition to providing a very good view, the M incision offers the opportunity to improve the papillae and the buccal contour to a limited extent. As it is a slightly more demanding technique than displacement, it is only indicated in rare cases involving the maxillary anterior region, provided the keratinized mucosa and volume are sufficient.
3.6.4 The roll flap
The roll flap is indicated in situations where, upon exposure, only buccal volume shows a deficit and the contours of the alveolar process need to be restored for esthetic reasons102,180 (Fig 3-43a to e). If, however, the keratinized and attached mucosa are also deficient, an apically advanced flap with a connective tissue graft is indicated. The roll flap was first described by Abrams in 19803 as a technique for the augmentation of edentulous alveolar processes. It was later modified by Scharf and Tarnow154 to be an exposure technique for implants.15
The incision of the roll flap technique begins with a partial-thickness, horizontal cut along the palatal edge of the implant. The vertical incisions, the length of which are determined by the volume required, may be placed in the sulcus of the adjacent teeth or paramarginally. A paramarginal incision line preserves the approximal papillary areas. The length of the incisions depends on the volume required. If the incisions are larger, the apical displacement of the mucogingival junction is also possible in some cases.14,85 Starting from the horizontal incision, the connective tissue layer in the area of the palate is prepared with an internal gingivectomy incision. When the connective tissue layer reaches dimensions adequate for the buccal volume defect, the periosteum is dissected apically and laterally, and the full-thickness flap consisting of connective tissue and periosteum is elevated to the buccal surface of the implant and the exposure site. The prepared palatal connective tissue and the periosteum will still pedicle on the vestibular flap. A pocket is then formed in the buccal soft tissue for the graft. This component may be rolled into a buccal pocket using a sling suture, which simultaneously fixes it to the buccal mucosal flap. Due to the two-layered preparation, the mucosal flap can be adapted without tension (Fig 3-44a to g). With only minor surgery being necessary, the roll flap increases the volume of the maxillary vestibular gingiva with the pedicle connective tissue from the palate, which will improve the quality of the buccal gingiva and give it stable long-term volume. This was confirmed in a prospective split-mouth study performed on 10 patients, to be published soon (Fig 3-45a to o).
3.6.5 The apically repositioned advanced flap
Grafted bone in the maxilla or mandible is normally covered at the end of the surgery through mobilization of the vestibular flap after dissection of the periosteum to guarantee a tension-free closure. This leads to palatal/lingual displacement of the vestibular keratinized gingiva and at the same time to a flat vestibule. In addition, by performing a grafting procedure without cutting the periosteum, as is the case in the tunnel approach, the vestibule becomes very flat. The correction of this situation can be performed in the mandible during implant insertion by using the Kazanjian vestibuloplasty approach. Another possibility is the apical displacement of the mucogingival border (i.e. in the mandible) due to a lack of tissue, an open vestibuloplasty leaving only the periosteum on the buccal bone to heal through open granulation.
As opposed to the mandible, soft tissue management mostly takes place in the maxilla during the exposure of the implant. Due to the different anatomy of the maxilla, it is possible to achieve an optimal shift of the mucogingival junction using a pedicled advanced flap. The phenomenon of the apical repositioning of the mucogingival junction and the resulting reduction of the vestibule can be frequently observed in the case of extensive augmentative measures in particular, and their primary wound closure or Rehrmann’s wound coverage technique. As in resective periodontal surgery,63 the apically advanced flap is an exposure method15 suited to form optimal keratinized and attached mucosa for implants. The great advantage of the maxilla is the presence of a wide surface of keratinized gingiva on the palatal side, which can be moved in the planned direction and into the desired position. For this reason, this kind of procedure is performed most frequently for the exposure of implants in the maxilla.
While the indication for a roll flap is the missing volume on the vestibular side, that for an apically repositioned flap is missing keratinized soft tissue in this area. At the beginning of the surgical procedure, the existing width of keratinized gingiva around the adjacent teeth is measured with a periodontal probe. An amount of 2 mm is added to the measured width before it is marked out, starting from the displaced mucogingival junction in the area of the implants toward the palate. The marking signals the position of the first supraperiosteal horizontal incision in the palate. For the repositioning of the flap, the incision line is continued mesially and distally at right angles, with vertical parallel supraperiosteal incisions into the vestibule. The vertical incisions should go beyond the mucogingival junction of the adjacent teeth by the initially measured width plus 5 mm. It is recommended to keep a distance of at least 1 mm to the adjacent periodontium. If there is a free-end edentulism in the maxilla, the distal incision line should enclose the region of the tuber maxillae, as a flap with a greater circumference is needed due to the later buccal displacement. The preparation of a mucosal flap optimally starts from the palatal side and does not result in the denudation of the bone in the case of partial-thickness dissection. The periosteum should be preserved to protect and nourish the recently augmented bone underneath and to contribute to regeneration and maturation without interruption.62 The partial-thickness flap is dissected deep into the vestibule with particular care when making the orovestibular incision, so that the flap volume can be precisely placed into the new site, and the thickness of the flap is greater than 1.5 mm.13 Then, the implants are exposed with individual semilunar incisions, and the tissue to be displaced is shifted aproximally or buccally where volume is needed. After the gingiva formers are inserted, the next step is the positioning with sutures of the apically advanced flap mesially and distally in the coronal area. Then, the mucosal flap is fixed to the alveolar process with periosteal sutures at the height of the later mucogingival junction, and protected from cheek and muscle movements, and therefore from later recrudescence. Further sutures through the periosteum and palatal mucosa can adapt the mucosal flap to the gingiva former. In the case of greater palatal areas, a palate plate helps secondary granulation (Figs 3-46a to o and 3-47a to g).
3.6.6 Apically advanced flap in combination with a connective tissue graft
The apically advanced flap primarily serves to create keratinized mucosa around the implant. If, however, in addition, the volume of the mucosa needs to be changed, the alveolar process contours need to be evened out or the mucosa needs to be shaped, the apically advanced flap can be combined with a connective tissue graft. The opportunity to achieve keratinized mucosa and the restoration of soft tissue contours at the same time makes this technique highly indicated in the maxillary anterior region following augmentation procedures. The excision of a connective tissue graft is based on the purpose of use; a large amount of moderately consistent connective tissue can be harvested from the palate, and connective tissue of high dimensional stability from the tuber region. This is recommended in esthetic areas or for the reconstruction of papillae tissue from the tuber maxillae with a high collagen content, which can be excised and covered in a wedge shape under the split-thickness flap if the incision line of the apically advanced flap is correspondingly extended in a distal direction. The graft from the palate is harvested using the single-incision technique without vertical releasing incisions,50 where the median horizontal incision line of the apically advanced flap should be used as access. It is recommended to leave a strip of connective tissue of a width of at least 3 mm between the donor site and the prepared split-thickness area for later safe readaptation and reepithelialization. When planning the procedure, the dimensions of the apically advanced flap should be determined based on the required size for repositioning of the mucogingival line, as the areas of the palate will be defined by the above-described median horizontal incision for the size of the connective tissue graft and cannot be changed.142 To improve the circulation and diffusion of the free graft after the apically advanced flap is prepared, the adjacent mucosal areas can be carefully tunneled and extended using a Beaver micro-SM69 blade and tunneling instruments, and the graft can then be slid into this approximately 5-mm–deep lateral pocket mesially and distally.
After positioning, the graft is fixed to the periosteum with resorbable sutures in the desired position, first along the mesiodistal axis and then along the interimplant axis. It is finally covered with the apically advanced flap (Fig 3-48a to j).
In the mandible, this technique can be used as an alternative to free gingival grafts. After the preparation of the apically repositioned flap on the vestibular and lingual sides, a long connective tissue graft is harvested from the palate and cut into two pieces. One piece is sutured internal of the lingual flap, and the other internal of the vestibular flap. At the end, the two flaps are sutured together around the gingiva former. The impression for the definitive restoration is performed at the earliest 5 weeks later (Fig 3-49a to h).
3.6.7 Free gingival grafts during exposure
Based on the description by Sullivan and Atkins,67,172,173 free gingival grafts are still a method of choice today for extending keratinized gingiva. If, until exposure, a deficit of keratinized attached gingiva is observed, it can be extended by way of a free gingival graft according to Björn and Nabers.20,127,128 This begins with a horizontal incision, followed by a two-layered dissection. The incision is placed in a way that guarantees the preservation of all keratinized gingiva lingually, particularly in cases involving the mandible. Greater attachment losses can be avoided this way,94,115 but more importantly, the anatomy of the region is taken into account, which makes later surgical procedures on the lingual side very difficult. When preparing the vestibule, the periosteum and also parts of the connective tissue in the area of the recipient site are preserved in order to prevent proven bone resorption and increased postoperative morbidity.51 The final preparation of the vestibuloplasty shows no movement in the recipient bed upon muscle activity and can be optimally fixed in the area of the vestibular fold on the periosteum, or if reattachment is not expected in the case of gingival grafts, allowed to granulate freely.
The size of the recipient site can be superimposed on the donor site using a template. The premolar area of the hard palate without rugae represents an ideal donor site. Alternatively, the tuber or edentulous areas of the jaw may also be used.164 In the next step, a 1-mm–deep incision is placed around the template – generously to compensate for shrinkage – with the incisions crossing on the corners. The epithelium with basal lamina is detached with a sharp blade in a split-thickness flap of a continuous thickness of about 1 mm. Compared with other graft thicknesses – from thin partial thickness (0.5 to 0.75 mm), through partial thickness (0.75 to 1.25 mm), to full thickness (1.25 to 1.75 mm) – thin grafts show greater immediate contraction but a lesser degree of postoperative shrinkage125,140,173 as well as better color adaptation to the surrounding tissue. Glandular or fatty tissue should be removed from the graft before its placement in the recipient bed.
After the graft is adapted, it is fixed with sutures and tissue histoacryl adhesive across its whole surface. It is recommended to begin with simple interrupted sutures on the coronal corners mesially and distally, and then to create close contact with the recipient bed with crossing mattress sutures, also looping around the gingiva formers. After suturing, the graft is carefully pressed into the recipient bed for 1 min with gauze soaked in saline solution. This close contact is decisive, as the intermediary formation of seroma may lead to a lack of diffusional nutrition by way of plasmatic circulation, and therefore to necrosis of the graft (Fig 3-50a to i). In the next step, tissue histoacryl adhesive can be additionally applied to the coronal sections of the graft and the horizontal incision line, which should be removed together with the sutures after a 14-day healing process.
From the experience of the authors, it is recommended not to do this type of procedure during implant exposure surgery, but to wait at least 1 year after the prosthetic restoration so as to minimize the resorption of the grafted bone, since the vascularization of the site is still incomplete 3 months after grafting and implant insertion.
The selection of the exposure procedure and soft tissue management is based on the anatomical situation following implantation. Three exposure procedures (the apically advanced flap, the roll flap, and the apically advanced flap with connective tissue graft) were compared.180 During a 12-month follow-up period, the apically advanced flap with or without a connective tissue graft showed a statistically significantly greater gain in attached mucosa, whereas the roll flap technique and the apically advanced flap with connective tissue graft resulted in a significant increase in soft tissue volume.180 Fagan and Freeman59 also found that apically advanced flaps represent an alternative to free gingival grafts. Although the risk of recrudescence is slightly higher in the case of advanced flaps, the related color adaptation and improved patient morbidity can be considered favorable.
3.6.8 Papilla construction during implant exposure
In addition to dental reconstruction, the esthetic success of implant therapy can be determined based on the pink esthetic score, which attributes great significance to the formation of the papillae based on several other criteria. Ideal soft tissue results begin with planning, tissue preservation, augmentative measures, and carefully considered prosthetic reconstruction,175,177,190 and rely on three-dimensionally correctly positioned implants.29,31,126 Not only the relationship with bone structures126,165 but also that with adjacent implants has to be taken into account. As a simple and generally applicable rule, a space of 1.5 mm is recommended between the teeth in a mesiodistal direction, and 3 mm between implants.139 The buccal bone walls on both sides should measure 1.5 to 2 mm, where the implant shoulder – also depending on the system used – should be positioned vertically 3 mm apically from the central facial margin of the planned restoration.17,30,69 In addition to the horizontal, vertical, and vestibulo-oral dimensions, the shape and size of the papillae can be described in terms of the approximal contact points created during prosthetic treatment.146 The space between the contact point and the crestal bone13 should be less than 6 mm in natural teeth, so that the entire interdental space between the tooth and the implant can be filled with a papilla. In the case of an implant–tooth scenario, a space of up to 4.5 to 5 mm results in the formation of a papilla to its full size,41,152 and between an implant and pontic, a distance of 5.5 mm is considered decisive.190 Interimplant papillae form if the vertical distance is not more than 3.5 mm,175,176 whereas this index could not be verifiably documented in prognoses even at 3 mm.87
In relation to the preparation of apically advanced flaps, Palacci and Nowzari133 described the detachment of semilunar flaps from the dissected buccal mucosal flap, prepared initially from the palate as an apically repositioned flap, with the purpose of placing these in a rotated position in the new papilla sections between the implants (Fig 3-51a to f). However, this technique or similar ones – such as the palatal sliding strip flap with pedicles of interimplant epithelial components4 – do not provide for sufficient volume for the formation of vertical papillae, and the horizontal incisions run relatively far into the palate. During a 12-month follow-up period, papillae modifications using Palacci flaps were found to result in an increase in papilla height in one third of the cases, while 58.3% showed a loss of papilla height.68
Rotating flaps of free connective tissue grafts combined with apically advanced flaps are recommended for the improvement of volume. Alternatively, semilunar or rotating flaps can also be dissected on the palatal side and fixed between implants (Fig 3-52a to d). This can also be combined with the roll flap technique.15,97,180 The roll flap technique does not always have to be used for papillae formation in a vestibulo-oral direction, but can also be used in a mesiodistal direction, prioritizing one papilla. In addition, a combination of a roll flap and free gingival grafts placed over the exposed bone or periosteum can be used to increase the vestibular volume of the soft tissue (Fig 3-53a to e). The pedicle connective tissue of a roll flap can also be used partly for the formation of an interimplant papilla (Fig 3-54a to g). A further pedicle variant of the apically advanced flap is the Tinti flap.179 After a small apically advanced flap is dissected, it is dissected once again in two layers from the apical to the coronal aspect, and following two internal vertical releasing incisions to create a pedicle, which can now be reflected coronally. As with gingival onlay grafts from the tuber or the lateral hard palate,97,131 all flaps have to be immobilized in order to heal. Immobilization plays a particularly important role in relation to connective tissue grafts and their periosteal diffusional nutrition.
3.6.9 Papilla reconstruction technique in the anterior maxilla
The presence of a heavy bony defect in the anterior area requires not only its reconstruction but also that of the soft tissue, since patients’ expectations are very high in the esthetic area. Reconstructing the soft tissue includes not only its volume but also the presence of adequate papillae without black triangles. For this purpose, intensive planning and strategizing needs to occur that takes into consideration the many important factors influencing the definitive result, including sometimes more than one soft tissue graft near the bony augmentation. During and after implant exposure, a number of mini flaps have to be rotated to different places, with or without additional soft tissue grafting, in order to reach the planned surgical goal (Fig 3-55a to o).
From a practical point of view, the first step is to increase the volume of the soft tissue in the esthetic area. This can be done using the different techniques described in this chapter, before or with the bone augmentation and with or after implant insertion. At the time of implant exposure, an apically repositioned flap is performed to displace keratinized gingiva back into the vestibule, exposing the connective tissue that covers the implants. This tissue is now partly punched, keeping the tissue pedicle on one side, depending on the planned direction of the tissue displacement. In case of the reconstruction of a papilla between two implants, the two punched tissues will still pedicle to the area between the implants. After elevation of the punched tissues, they will be sutured together between the two implants, increasing the height of the interimplant soft tissue (Fig 3-35s and t). A number of rotation flaps can be prepared from the vestibular flap as well as from the palatal mucosa in order to cover the punched tissue and increase the height of the interimplant papilla (Fig 3-35v to x).
A similar procedure is performed to increase the papilla between an implant and its neighboring tooth: In this case, the pedicle of the punched tissue is left in the area that has to be augmented. In situations where thick soft tissue over the implant is missing, a palatal connective tissue flap and or palatal mucosal flaps can be used for the papilla reconstruction (Fig 3-56a to j).
3.6.10 Emergence profile shaping
Papillae can sometimes be created by shaping the emergence profile without any surgical measures.65,87,129 This occurs in a healthy periodontal area without any tooth recession, where implants are inserted in sufficient bone in a thick soft tissue biotype. In particular, in the first 3 years, over half of all papillae (58%) around these individual implants can regenerate without additional surgical intervention,87 and even showed an increase in papilla height in 80% of the cases. However, this is not the case in heavy bone and soft tissue defects, where complicated procedures are required for rebuilding the lost bone and soft tissue.
As with all mucogingival surgical measures – depending on the esthetic significance of the given region – often 8 weeks (or sometimes even significantly more time) has to pass before final prosthetic reconstruction can be performed. Until such time, when the soft tissue is not only completely healed but also stable again, provisional treatments can be beneficial, also for protecting and shaping the soft tissue cuff around implants.
Various measures can be taken during the provisional treatment phase to preserve and improve the implant site. Temporary prostheses are primarily intended to bridge a period of time in terms of function and esthetics, but a secondary function may also be to support soft tissue formation.
The emergence profile is defined as the transitional area between the circular cross-section of the implant and the individual profile of the crown, located in the area where the implant emerges from the surrounding soft tissue. An optimal emergence profile enables an ideal physiologic crown shape in the area of the emergence site on Margo mucosalis.
The soft tissue emergence profile is formed by gingiva formers as well as temporary crowns fastened with screws in the case of transgingival healing or after exposure. Care must be taken not to exert any pressure on the vestibular gingiva, if possible, in order to prevent recessions. It may also be necessary in some cases to fabricate customized peek abutments for healing.
3.6.11 Clinical and laboratory procedures for the creation of temporary crowns
In an ideal case, the creation of temporary crowns and the intraoperative registration of the implant position is necessary upon implant insertion during the treatment phase. The emergence profile is then created on the master model and transferred to the final prosthesis. After implant exposure, and in particular in the case of the immediate placement of single implants, the immediate integration of a fixed temporary crown on the temporary peek abutment has great advantages. However, this is not the situation when bone has to be reconstructed: in this case, there is no immediate implantation, and the grafted bone has to heal submerged.
The insertion of a provisional prosthetic, which is performed about 4 weeks after implant exposure, usually involves considerable difficulties. An appropriately shaped provisional crown can also ensure soft tissue conditioning, which improves the final esthetic effect. It may be reasonable to shape the provisional crown, e.g. by repeated adjustments of its emergence profile, until individually optimal soft tissue conditions are achieved.21 The emergence profile of the provisional crown thereby achieved can be transferred to the final impression.
In the case of temporary prostheses fabricated chairside, a provisional abutment is screwed onto the implant and adjusted to the correct size and shape in or outside the mouth. In the end, a temporary composite crown is created on the abutment and screwed in with the help of a miniplast splint. The ideal emergence profile can then be corrected extraorally step by step using a composite until the final shape is reached. If composite is added to the cervical crown parts, soft tissue anemia should not last for more than 5 min, otherwise the shaping has to be performed in multiple steps.39,58,129 Provisional metal or composite abutments are suitable for this treatment. The screwed and cemented temporary crown can be produced, for example, from a natural dental crown or from a plastic cap prepared in a laboratory.48
The goal of the implant–prosthetic procedure is not only to create an optimal suprastructure but also natural-looking soft tissue. The decisive criteria are:
1. The level of the gingival margin corresponds to that on the contralateral natural tooth.
2. The bone contour in the area of the implant is the same as that in the contralateral area.
3. The area of the attached gingiva is as wide as that on the contralateral natural tooth.
4. There are no scars.
5. The papillae are preserved or recreated and fill the interdental triangles in the same way as in in the contralateral area.
6. The soft tissue color harmonizes with the overall conditions.
7. The implant crown cannot be identified as a replacement crown.
8. The conditions are stable in the long term.