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S. Nares (ed.)Advances in Periodontal Surgeryhttps://doi.org/10.1007/978-3-030-12310-9_9
9. Coronally Positioned Flaps and Tunneling
Gingival recessionGingival recession/surgeryGingival recession/therapyMucogingival surgeryPeriodontal plastic surgeryGingival augmentationRoot coverage
Patients often present with a variety of soft tissue defects around teeth and implants that can lead to functional and esthetic problems. An array of surgical procedures has been developed to manage these soft tissue defects. The initial procedures were mainly resective in nature and aimed at correcting aberrant frenum attachments, shallow vestibules, and inadequate attached gingiva. These procedures were collectively referred to as “mucogingival surgery” . In recent years, surgical procedures to deal with soft tissue deficiencies have been refined and have incorporated regenerative therapies, as well as adopted the goal of esthetic enhancement. This broadening of the range of surgical procedures leads to the introduction of “periodontal plastic surgery,” as a new term, coined by Miller . Soft tissue abnormalities could be treated in a predictable manner, improving soft tissue health, function, and esthetics .
9.2 Scope of the Problem: How Common Is Gingival Recession?
Gingival recession is characterized by apical migration of the gingival margin from the cementoenamel junction (CEJ), with concomitant exposure of the root surface. The root exposure associated with gingival recession can have negative esthetic sequelae, as well as predispose the site to dentinal hypersensitivity and root caries .
The prevalence of gingival recession can vary substantially among the specific study populations. In North America, it has been described in one epidemiological study in 78–100% of middle-aged individuals, potentially affecting 22–53% of the teeth . In another study, the prevalence of 1 mm or more recession in American population aged 30 years and older was 58% and increased with age . In Brazil, a more recent study showed that 89% of the adults presented with gingival recession . In addition, other epidemiological studies demonstrated that adult subjects showed a prevalence of gingival recession of 51% in Norway  and of 68% in Finland . Overall, gingival recession is a highly prevalent condition, which progressively increases with age.
The identification of potential etiological factors in the induction of gingival recession is critical in managing those risk factors in the course of therapy. The literature has described many possible factors, though their causality has not been established. Anatomical, physiological, pathological disease-related, and mechanical factors have been suggested [10, 11].
Periodontal or tooth anatomy can play a role in the apical migration of the gingival margin. Inadequate zone of attached gingiva, high frenum or muscle insertions, tooth malalignment, and excessive root prominences with associated thin alveolar bone are believed to predispose to the development of recession. Ectopic positioning of roots outside of the alveolar bone envelope, following orthodontic tooth movement, may also lead to gingival recession. Mechanical trauma encompasses various forms of injury to the tissue, including improper tooth brushing, intraoral piercings, prosthetic appliances, aggressive tooth preparation procedures, overhanging restorative margins, invading the biologic width, and tobacco chewing.
Pathologic conditions, such as inflammation associated with periodontitis, lead to apical migration of periodontal attachment and in some cases, resulting in gingival recession.
Successful therapy is predicated on effective removal of the causative factors prior to any periodontal plastic procedure to avoid recurrence.
9.4 Risk Assessment
In addition to the etiological factors, there are certain patient- and site-related factors that can put patients at a greater risk for developing gingival recession. Increased age, male gender, high plaque index, tobacco smoking, and number of missing teeth are patient-related factors that have been associated with the extent and severity of gingival recession [12, 13]. Malpositioned teeth (rotated or too buccally/lingually inclined), teeth with a thin gingival biotype, with excessive frenum pull, with advanced periodontal disease, and/or with subgingival restorative margins have also been correlated with a higher possibility of gingival recession. Although each of these factors has been associated with gingival recession, the presence of multiple factors may significantly increase the risk of developing or exacerbating gingival recession. Therefore, risk assessment should consider each of the elements as well as the number of risk indicators identified in order to develop an effective strategy to mitigate those risks.
9.5 Classification of Gingival Recession Defects
Different classification systems have been used throughout the years to describe gingival recession. Initial attempts at classification measured recession width and depth to classify recession into four categories using the descriptive terms “shallow,” “deep,” “narrow,” and “wide” . The index of recession (IR) was later introduced and was mainly used in cross-sectional and longitudinal epidemiological studies to describe the prevalence, incidence, and severity of gingival recession . It categorized recession by two digits, separated by a dash, such as “F3–6.” The letter F or L referred to facial or lingual recession, respectively. The digits denote the horizontal width and vertical height of the recession. The classification proposed by Miller is currently the most widely used classification . This system is based on vertical soft tissue loss in relation to the mucogingival junction (MGJ), as well as the level of interproximal periodontal tissue loss. It categorizes defects into four classes. Miller Class I describes gingival recession, which ends coronal to the MGJ, whereas the denuded root defect extends to the MJG in Class II. The interproximal attachment and bone are intact in Class I and II gingival recession defects, while it is mild/moderate in Class III and severe in Class IV, extending beyond the midfacial recession. Miller correlated the classification to the expected prognosis of root coverage, where complete root coverage was predicted in Class I and II, while only partial root coverage was expected in Class III defects, and unpredictable outcome was anticipated in Class IV sites.
The scientific community has expressed some doubts of this classification system, including the uncertainty of the amount of interproximal attachment loss, the unknown influence of tooth malposition, and the difficult distinction between Class I and II gingival recession. To solve such limitations, Cairo introduced a new classification system, based on the identification of the interproximal clinical attachment level to predict the outcome of therapy . Three recession categories were described in this classification: RT1, exhibiting no interproximal attachment loss; RT2 showing interproximal attachment loss equal or less than the facial defect; RT3 presenting with interproximal attachment loss greater than the facial defect. The degree of facial root coverage anticipated by the RT classification was projected to be limited by the interproximal attachment level. Therefore, root coverage has been suggested to be more predictable in RT1 and RT2 than RT3.
9.6 Rationale for Therapy
9.6.1 Progression of Gingival Recession with or Without Therapy
Multiple lines of evidence have suggested that gingival recession defects are progressive in nature. A longitudinal study with 12-year follow-up demonstrated that gingival recession increases with age and sites with existing gingival recession are at the greater risk of progression . In a retrospective 10- to 27-year follow-up split-mouth study, gingival recession defects, lacking attached gingiva treated with free gingival graft on one side of the mouth, were compared with untreated contralateral sites . Results demonstrated that treatment was effective, since all treated sites exhibited reduced gingival recession and increased stable keratinized gingiva. In contrast, untreated sites showed increased gingival recession during follow-up period.
A systematic review and meta-analysis of untreated gingival recession defects has indicated increased risk of progression of recession during long-term follow-up . There is also some limited evidence to support a protective role for keratinized gingiva in reducing the likelihood of gingival recession progression. As a result, the surgical correction of these defects via soft tissue augmentation and root coverage appears as an important intervention to be considered during the clinical decision-making process.
The main reason that drives many patients to seek periodontal treatment are esthetic concerns. Patients demand treatment when excessively long teeth and/or a lack of harmony in the gingival margins are evident while smiling. The most feasible treatment to correct this esthetic gingival imbalance is root coverage procedures. A recent systematic review of randomized controlled trials demonstrated that periodontal plastic surgery procedures for the treatment of single and multiple gingival recessions improve esthetics, both perceived by patients and objectively assessed by professionals .
Teeth with gingival recession often experience pain in response to thermal, chemical, and tactile stimuli to the exposed dentine. This phenomenon is known as “dentinal hypersensitivity.” The pain is commonly sharp, short, and localized and can severely affect performance of proper oral hygiene. The treatment for dentinal hypersensitivity can be complex and may include local application of desensitizing agents to occlude exposed dentinal tubules for mild cases with no esthetic concerns. Cervical restoration can be performed in cases where there has been enamel loss, exposing dentine coronal to the CEJ. Surgical intervention to achieve root coverage is another strategy, primarily indicated when complete root coverage can be predicted. A systematic review has suggested that there is not enough evidence to prove that mucogingival surgical procedures can resolve dentinal hypersensitivity .
This is attributed to the fact that dentinal hypersensitivity has not been consistently evaluated in clinical studies. Nonetheless, several studies have demonstrated improvement in dentinal hypersensitivity. One reason why dentinal hypersensitivity is not consistently resolved is because incomplete root coverage can be associated with residual dentinal hypersensitivity. Therefore, root coverage can be proposed as a viable therapeutic option for patients who complain of dentinal hypersensitivity, only if complete root coverage is technically feasible.
Keratinized Tissue Augmentation
Gingival recession defects with thin, minimal, or no keratinized gingiva have been considered to be at greatest risk of progression . Therefore, keratinized tissue gain has been considered one of the therapeutic objectives of periodontal plastic surgery. However, it may be debatable whether gingival thickness or the keratinized phenotype of the gingiva is the most important element of risk. The fact that many types of grafting, which do not necessarily mediate clinically significant increase in keratinized gingival zone, are associated with periodontal attachment level stability may argue that gingival margin thickness is more important than keratinization phenotype. Moreover, some of the therapies aimed at increasing keratinized gingival zone, such as free gingival graft, are associated with diminished esthetic and suggest a secondary role for keratinized gingiva in periodontal plastic surgery.
Cervical Caries and Non-carious Cervical Lesions
In the elderly population, radicular caries and/or deep root abrasion are common findings and can pose oral hygiene challenges for patients . These can lead to dentinal hypersensitivity and/or endodontic involvement. The combination of root coverage surgery and restorative treatment in these teeth can help prevent future caries development and render an easier situation for plaque control for the patient. However, one needs to consider that dentinal bonding is not as predictable as enamel bonding. Therefore, bonded restorations in dentin may be more prone to leakage or failure.
9.7 Techniques for Gingival Recession Therapy
Multiple approaches to the treatment of gingival recession defects have been described in the literature, including the coronally advanced flap (CAF) with or without an additional graft, intra-sulcular tunneling (IST), pedicle flaps, free gingival graft (FGG), guided tissue regeneration (GTR), and vestibular incision subperiosteal tunnel access (VISTA). Each of these techniques has advantages and disadvantages.
9.7.1 Free Gingival Graft
A number of investigators have pioneered the technique of free gingival graft , as well as its application for vestibular extension , root coverage , and for pre-prosthetic augmentation of attached gingiva . In 1968 Sullivan and Atkins  outlined the biologic basis of FGG and the wound healing process, subsequent to FGG therapy.
Free gingival graft offers a number of advantages and disadvantages. The advantages include increase in zone of keratinized attached gingiva and vestibular depth. The disadvantages include limited ability for root coverage and mismatch of surface contour, texture, and color, which can result in compromised esthetics.
9.7.2 Coronally Advanced Flap
CAF is perhaps the most documented procedure for the treatment of single and multiple gingival recession defects. Norberg is credited as describing a procedure that involved coronal positioning of gingiva. Bernimoulin et al. were the first to report on CAF in 1975 for the treatment of gingival recessions . This procedure has undergone a number of refinements, including by Allen and Miller in 1989 , Pini Prato et al. in 1992, Zucchelli and De Sanctis in 2000, and De Sanctis and Zucchelli in 2007. CAF has been performed either without additional graft, subsequent to FGG, in conjunction with a barrier membrane as GTR, or most commonly along with the subepithelial connective tissue graft (SCTG).
The coronally advanced flap for the treatment of single-tooth recession defects is designed with two horizontal beveled interproximal incisions on each side of the recession defect . The incisions are made at a level which measures the recession depth plus 1 mm apical to the papillae tips. Additionally, two relatively short beveled vertical releasing incisions are made. These incisions, which are elevated by partial-thickness dissection, start coronally at the lateral ends of the horizontal incisions and extend apically to the alveolar mucosa. A trapezoid-shaped flap is elevated, starting with partial-thickness dissection of the surgical papilla. Full-thickness flap elevation of the soft tissue apical to the gingival recession zenith is carried out to approximately 3 mm apical to the bone dehiscence. Partial-thickness flap elevation is carried out to mobilize the flap in order to coronally position the flap with minimal tension. The papillae are de-epithelialized in order to create a vascular bed for the elevated flap which will be sutured coronal to the CEJ in the papillae, using sling sutures.
To treat multiple recession defects, interdental submarginal incisions and an envelope flap using split–full–split are employed . The flap is extended at least one to two teeth on either side of the affected teeth to allow for low-tension coronal advancement of the flap.
This technique offers many advantages, including the ability to treat single, as well as multiple recession defects. CAF provides good access to the treatment site, allowing the operator the flexibility to perform full- as well as partial-thickness flaps in an effort to reduce the flap tension for optimal coronal advancement. The main drawback of this technique includes the scar formation associated with the incision line . Previous studies have demonstrated that flap tension is a negative predictor of root coverage, and procedures which reduce flap tension can lead to better root coverage. Similarly, positioning of the gingival margin at least 2 mm coronal to the CEJ can lead to increased likelihood of achieving complete root coverage . One of the major risk factors for root coverage outcome is flap thickness . In cases where flap thickness is less than 0.8 mm, there is decreased likelihood of root coverage. In a recent prospective clinical study, it has been demonstrated that flap thickness was a negative predictor of root coverage only in those cases where CAF was performed without additional graft . In cases where SCTG was used in conjunction with CAF, flap thickness was not a risk factor. Therefore, clinicians can use this information to conclude that in cases with thin mucosa, additional grafting may be utilized.
9.7.3 Intra-sulcular Tunneling (IST)
In 1985, Raetzke pioneered the “envelope” flap that was created by partial-thickness dissection for covering localized areas of root exposure . The envelope flap was formed by an undermining partial-thickness incision in the tissues surrounding the defect and a free SCTG positioned directly over the root dehiscence. In 1994, Allen offered a modification of the Raetzke envelope by creating a partial-thickness supra-periosteal envelope for the treatment of multiple gingival recession defects . This approach entailed partial-thickness undermining dissection through the papillae to allow for coronal advancement of the flap. In 1999 Zabalegui et al. coined “the tunnel” technique by offering a more detailed protocol . This report outlined a strategy to undermine the papillae with partial-thickness dissection through intra-sulcular incision without any surface incisions. The partial-thickness dissection is carried out beyond the mucogingival junction, not to reposition the flap but to allow for insertion of SCTG. Further refinements of the tunnel technique have been offered by coronal reposition of the gingival margin, using double-crossed sutures, which are slung over interproximal embrasures that are blocked with temporary bonded resin restorations .