The free gingival graft

Aetiology

Recession can have a multifactorial aetiology and, therefore, a careful history and examination are required, as well as appropriate investigation of the affected sites (Table 1). The mechanism of recession is not fully understood, but the presence of persistent inflammation is required to lead to recession. Such inflammation can lead to the breakdown of the underlying connective tissue, which eventually leads to gingival tissue recession. Causes of inflammation can be mechanical, such as overzealous brushing³ or the use of overly hard bristles. Traumatic occlusion can also lead to recession in cases of a deep overbite in incisal Class 2 or 3 relationships where the incisal edges can directly contact the soft gingival tissues. Inflammation can also be attributed to a bacterial aetiology, where persistent plaque presence can lead to an inflammatory host response and, if left untreated, may develop into periodontitis.⁴ Tongue studs and lip piercings are also associated with recession. Individuals with tongue studs can have up to an 11-times greater chance of lingual recession of the mandibular incisors compared to non-users.⁵ Meanwhile, lip piercings that are positioned close to the cemento-enamel junction (CEJ) are associated with buccal/labial recessions.⁶ Both objects increase the risk of recession with long-term use.

Presence of keratinized tissue

Keratinized tissue (KT) is the part of the oral mucosa that covers the gingiva and hard palate, extending from the gingival margin to the mucogingival junction. It is composed of the free and attached gingiva. The gingival width varies throughout the oral cavity, with the buccal gingiva generally widest at the incisors and narrowest in the premolar region,⁷ while for the lower lingual aspect, it is narrowest at the lower incisors and widest at the molar region. It was previously thought that an adequate amount of KT around a tooth was important to maintain gingival health and prevent recession. The argument was that a narrow zone of KT would be less resistant to frictional forces during mastication, and a moveable gingival margin can result in inadequate pocket closure with eventual formation of subgingival plaque.⁸ Furthermore, the presence of a shallow vestibule would favour food-particle accumulation and impede a patient's oral hygiene.⁹ There were various opinions on the necessary amount of KT needed for the prevention of recession, ranging from more than 3 mm,¹⁰ to <1 mm¹¹ with the most popular opinion being at least 2 mm.¹²

More recent studies have suggested that this may not be true. In 1980, Dorfman and colleagues reported results of a split-mouth study of 92 patients with bilateral sites with inadequate KT.¹³ One side had a free gingival graft (FGG) placed, while the contralateral side was treated as the control and monitored. After 2 years of close follow-up, no difference in the presence of recession between the experimental and control side was reported. Hence, it was concluded that gingival health can be maintained regardless of the dimensions of the gingival unit, and it is not linked to KT. The patients in the study were followed for up to 6 years and the initial findings were confirmed.¹⁴ In summary, it is not essential for KT to be present to maintain gingival health, but it is easier to maintain plaque control around teeth and implant sites with adequate KT because patients may experience discomfort when only lining mucosa is present.

Complications of recession

Patients can complain of, or have several, complications as a result of the presence of a recession defect. Some patients are concerned that the recession defect will continue to progress and accelerate, although evidence shows that this is unlikely to lead to tooth loss.¹⁵ Patients can also be concerned with poor aesthetics with interdental recession leading to the formation of black triangles, and labial recession leading to root exposure. The increase in crown height may affect a patient's appearance, particularly for those with a high smile line. Furthermore, sensitivity to hot and cold temperatures can develop as a result of exposure of the cementum and dentine. There can also be discomfort and difficulty brushing such areas because the more apical gingival margin can be difficult to access with the loss of KT. Overzealous brushing of the root can then lead to non-carious cervical lesions (NCCL) because the cementum/dentine surface is less resistant compared to the enamel surface of the crown.

Management of recession defects

Management of recession includes the following steps:

The free gingival graft

Introduced by Bjorn in 1963¹⁶ and refined by Sullivan and Atkins in 1968,¹⁷ the free gingival graft technique was indicated for covering recession defects. Its success in covering recession varies from 11% to 100%.¹⁸ The main advantages of such a technique were to increase the vestibular depth and KT, as well as to increase the gingival thickness. This ameliorates the ability of the patient to access and clean the gingival margin comfortably. This technique has several disadvantages. There is a poor aesthetic appearance owing to the mismatch in the colour of the graft, which is usually more pale and pink compared to the adjacent tissues, and the misalignment of the mucogingival junction (MGJ) following surgery; however, over time the tissues align,¹⁹ as it is thought that the MGJ position is genetically predetermined.²⁰Table 3 gives a summary of indications and contraindications.

Pre-operative preparation

Following a full history and examination, as well as a discussion of patient expectations, several factors should be covered concerning the clinical recession of the associated teeth (Table 4). Originally, recession defects were classified using the Miller index.²¹ However, there are several shortcomings. These include the lack of information on soft-tissue thickness and hard-tissue characteristics, such as NCCL and the presence of a CEJ. Therefore, the authors recommend the use of the recession matrix, which incorporates the data needed, as well as the Cairo classification²² for recession defects.

The recession classification states that:

Before placement of a free gingival graft, the patient should have a course of non-surgical therapy. This involves educating the patient on the correct atraumatic brushing technique where indicated, as well as the removal of any plaque-retentive factors that could cause chronic inflammation. This can lead to resolution in some patients, without the need for further surgery. Additionally, good oral hygiene is a prerequisite to ensure that the patient will be compliant and maintain the gingival site following grafting, thus reducing the risk of failure of the free gingival graft. A widely used threshold of a 20% plaque score is the minimum recommended before continuing to surgery (Figure 1).

If the marginal inflammation persists, or the patient continues to experience difficulty cleaning areas owing to brushing sensitivity, and provided all the alternative treatment options have been discussed, the patient can be considered for a free gingival graft. The authors recommend that such mucogingival surgery would require training before implementing in practice.

Moreover, before surgery, it is worth considering the construction of an upper palatal healing plate, which can be made following an upper arch impression of the palate and associated teeth (Figure 2). The plate acts to apply pressure to the donor site following grafting to provide blood clot stability, as well as to protect the wound area during the early stages of healing from changes in temperature and food debris. Lastly, splinting of the affected teeth is important particularly when grade 2 mobility is present to ensure the graft is stable during healing. Early movement of the graft can lead to failure and necrosis.

Free gingival graft technique

At the beginning of the procedure, the root surface should be thoroughly debrided to remove any plaque. This can be done intra-operatively once a recipient bed is made, but there is a risk of removing connective tissue fibres and healthy cementum, which can be useful in achieving creeping attachment in the long term.²³ Hence, the operator should measure the clinical attachment loss present at the recession site prior to the recipient bed preparation and use the measurement to guide the level at which the professional mechanical plaque removal is provided.

A 3-mm wide lateral and apical incision to the recession defect is prepared with a scalpel blade using a split-thickness approach whereby connective tissue and periosteum remains without exposure to the underlying bone (Figure 3). This ensures that the epithelium is removed to allow acceptance of a graft from a recipient site and also provides a bed of blood supply for the graft to integrate. The horizontal level of the incision should be at the level of the mucogingival junction and in case of no KT remaining, the incision should be made around the level of the gingival margin. Any presence of frenal involvement that would impact the stability of the graft should be removed and underlying fibres scaled to ensure no frenal relapse.

Following bed preparation, a template is used to approximate the width and length of the FGG needed from the donor site. The template can be made of foil or the paper card of a sterile suture (Figure 4). The template should be adapted with suture scissors in a way that fits the recipient bed. A graft that is too small will mainly overlie the avascular surface of the root surface and risk necrosis, while one that is too large will lead to comorbidities for the patient and possible failure of integration of the graft if the donor tissue extends beyond the connective tissue bed.

The template is transferred to the palate where the donor site is chosen and shallow incisions are demarcated to outline the graft. Ideally, the graft should be taken at least 2 mm away from the gingival margin of the maxillary teeth. Furthermore, the clinician should be aware of the position of the greater palatal foramen, which contains the greater palatine artery and nerve, as well as the path of these vessels in the palate, as iatrogenic damage to such sites can lead to severe bleeding and/or nerve damage. Lastly, the quality of the tissue should be considered and, therefore, rugae should be avoided when possible. Hence, the graft is normally taken using a new scalpel blade from the mesial line angle of the upper first premolar to the distal line angle of the first or second molar (Figure 5).

The graft thickness should be approximately 1–1.5 mm. A graft that is too thick can lead to delayed healing and poor circulation, while a graft that is too thin means there is little connective tissue present and necrosis can lead to graft failure.²⁴

The assistant should use compressed gauze at the donor site to temporarily achieve haemostasis while the clinician ensures that the graft has any fatty tissue remnants removed, followed by careful placement at the recipient site.

The graft is immobilized with simple interrupted sutures laterally followed by insertion of cross-sling sutures to compress the graft to the recipient site. Space between the graft and bed can lead to the formation of a blood clot that can inhibit the early stages of plasma circulation crucial for integration of the graft (Figure 6). Therefore, following successful suturing, a damp gauze is used to place firm pressure on the graft for 5 minutes.

At this point, the donor site should be fully assessed for haemostasis (Figure 7). An absorbable haemostat and cross-sling sutures can be used to further promote haemostasis, as well as advising the patient to wear the healing plate for added support.

Post-operative care

The patient should avoid pulling the lip during the 2 weeks after surgery. This is to prevent mobility of the graft and loosening of the sutures. The sutures ideally should be removed 2 weeks after the surgery (Figures 8 and 9).

For a few post-operative days, a soft diet and avoidance of spicy or salty food, which can exacerbate discomfort, is advised. The patient should avoid brushing the recipient site. Instead, they are recommended to rinse gently with chlorhexidine mouthwash twice daily until suture removal. Analgesics, especially for the first few days, can alleviate any pain. The patient should be given a contact for emergencies or when post-operative bleeding does not stop with local measures. Gentle brushing can resume around 2 weeks post-surgery, with interdental brushing at 3 weeks.

Clinical outcomes

If the graft successfully integrates at the recipient site, the patient should note a reduction in discomfort while brushing the gingival margin of the associated teeth. The patient would also have easier access to the gingival margin of the graft-associated teeth due to the increase in vestibular height and removal of any frenal involvement. In some cases, the graft may lead to creeping attachment, which can occur up to 12 months post-treatment (Figure 10). It is thought that the reason for this is due to coronal migration of the long junctional epithelium.²³ The gingival phenotype in the grafted area could also change from thin to thick, which is associated with less gingival recessions (Figure 11).²⁵

In terms of root coverage, the available literature suggests that the results can be unpredictable, with the mean percentage root coverage ranging from 11% to 87%, with the greatest success in narrow and shallow recession defects.¹⁸ The results are generally inferior when compared to a coronally advanced flap alone, or when combined with a graft.²⁶ Of 228 patients who underwent mucogingival procedures analysed by Griffin and colleagues,²⁷ it was found that patients with FGG procedures were three times more likely to develop post-operative pain and bleeding compared to connective tissue graft (CTG) procedures. This is attributed to the donor site healing whereby FGG surgeries inevitably lead to secondary intention healing. Interestingly, Zucchelli²⁸ suggested that there is no difference in post-operative pain for either FGGs or CTGs, and that the discomfort for patients corresponds to the remaining palatal tissue thickness of the donor site.

Modifications of the technique

Several modifications to the original technique have been made to attempt to improve on the technique's shortcomings. Bernimoulin and colleagues²⁹ were the first to describe a two-stage technique in which a coronally advanced flap of the graft site was achieved 2 months post FGG placement. The technique attempted to improve on root coverage as the authors reported that part of the FGG covering the denuded root surface failed to survive. Another modification described by Rateitschak in 1985, described as the accordion technique, aimed to cover a wide recipient bed.³⁰ The graft taken from the donor site is expanded in width with alternating incisions to allow it to cover a greater distance by changing the configuration of the graft. However, the new shape of the graft leads to areas with no coverage from the graft. A similar technique by Han and colleagues³¹ described obtaining minimum 2-mm wide strips of donor tissue, which are then sutured to the recipient site. The aim was to reduce the number of surgical procedures of gingival augmentation in cases of generalized lack of keratinized tissue.

Lastly, the partly epithelialized free gingival graft technique described by Cortellini and co-authors³² focused on bypassing the poor aesthetics of the free gingival graft, as well as the difficulty of coronally advancing the flap for a second stage owing to the relatively shallow vestibule in commonly indicated recipient sites for the lower incisors. The technique involves de-epithelializing the apical part of the graft, which is placed between the dissected alveolar mucosa and the periosteum of the recipient bed and extended 2–3 mm apical to the bone dehiscence. The epithelialized part is measured so that it extends from the CEJ to the position of the MGJ. Patient-reported outcomes from the case series are comparable to other well-founded mucogingival techniques.

Conclusion

The free gingival graft technique is a predictable procedure indicated for the patient who persistently finds it uncomfortable to effectively clean sites that lack KT on teeth and implants. General dental practitioners should be aware of such mucogingival procedures and it is a relatively simple technique for clinicians who are willing to undergo further training in mucogingival surgery.

Even with the introduction of techniques, such as tunnelling/rotational flap associated with CTG, the FGG is by no means an obsolete technique. The original technique and its variations could still be successfully used for recession cases, especially in those with a lack of keratinized gingiva, a prominent and thick associated frenal attachment and/or reduced vestibulum width.