Multiple factors influence the success of implant surgery. These include careful treatment planning, a command of the basic surgical techniques common to all oral surgery procedures, and the ability to perform these procedures atraumatically. One such procedure is closure of any soft tissue flaps that were elevated during surgery. The aim of flap closure is to reposition the soft tissues in a good anatomical position. Satisfactory closure of surgical wounds promotes healing and reduces complications such as wound breakdown, dehiscence, and infection. These factors play an important role in achieving successful and esthetic surgical outcomes. This module will focus on flap closure for oral surgery related to implant procedures.

After completing this ITI Academy Module, you should be able to: describe the general principles of surgical flap closure, including the process of wound healing; describe the principles of surgical flap closure following extractions; describe the principles of surgical flap closure for implant surgery; and explain the complications associated with flap closure.

The purpose of flap closure is to promote and optimize healing and, in doing so, to reduce complications. The flap must be closed in such a way as to achieve a good esthetic and functional outcome. This in turn will increase the chance of overall treatment success. The specific aims of flap closure include repositioning the soft tissues in the right anatomical position both to cover bone and to compress blood vessels in order to achieve hemostasis. The closure should support the flap in such a position to approximate the wound edges and encourage healing by primary intention. The flap should be positioned passively and should not be placed under tension. Too much tension leads to ischemia and wound breakdown.

There are two options for soft tissue closure, depending on the clinical situation. Complete closure, with the edges of the surgical wound fully approximated, will provide full mucosal coverage of the surgical site. This is termed primary closure. Alternatively the clinical situation may require that the flap be repositioned in the correct anatomical position without full coverage of the surgical site, for example, around an extraction socket or a healing abutment in a one-stage transmucosal implant placement. The aim of both options is to promote healing with the soft tissues in the correct anatomical position.

A key consideration in flap closure is healing. In healing by primary intention, the wound edges are placed in the correct anatomical position and allowed to heal. In oral surgery, sharp incisions with a scalpel blade produce neat wound edges with very little damage. When the wound edges are approximated, that is, brought together edge to edge, healing begins quickly. This process is known as healing by primary or first intention. The soft tissue union occurs rapidly, but this union is weak. Sutures provide support and stability to the soft tissues as the closed wound strengthens over time.

This diagram outlines the process of healing by primary intention. After the wound edges are approximated, thrombosis (or localized coagulation) occurs in any small blood vessels that have been cut. Epithelial cells proliferate and spread out until the wound is covered. Fibrin forms linkages across the wound, creating a weak union or joint. Next, capillaries proliferate across the small gap between the wound edges. Fibroblasts migrate into the fibrin framework and secrete collagen, which increases the strength of the union of the wound.

In contrast, healing by secondary intention occurs when the soft tissues are repositioned so that a gap remains between wound edges, for example, if tissue loss has occurred that prevents close approximation of the edges. Healing by secondary intention may also occur if there are postoperative complications such as wound dehiscence. These wounds heal through the formation of granulation tissue from the base of the wound outwards. This process takes longer than healing by primary intention and results in the formation of more scar tissue.

In healing by secondary intention, the small vessels that were cut or damaged hemorrhage into the surgical defect. Platelets aggregate, and a thrombus or clot forms. Inflammatory cells are attracted to the site. Macrophages migrate into the wound and remove necrotic tissue and fibrin. Growth factors promote epithelial and subepithelial tissue proliferation. The wound is then repaired from the base upwards with the formation of granulation tissue. Epithelial cells also proliferate and spread out until the wound is covered.

The planning for flap closure should start prior to surgery. The treatment planning will determine which kind of flap is suitable for the surgical procedure. Treatment planning will also reveal if a periosteal releasing incision may be necessary in order to obtain a tension-free flap for the subsequent closure. The ITI Academy Learning Module on 'Flap Design' discusses basic principles for oral surgery in general and for surgical implant procedures. Once the surgical procedure has been completed and the wound has been properly irrigated and debrided, the surgeon must return the flap to its original position. Important landmarks must be repositioned to achieve the correct anatomical positioning of the flap.

Suturing is performed from the mobile raised flap to adjacent immobile soft tissue. A slight reflection of the immobile soft tissue will ease the placing of sutures. In addition to the surgical site itself, relieving incisions and all papillae included in the flap must also be closed.

This clinical example demonstrates the correct order of flap closure. The first suture is placed across the papilla where the vertical releasing incision was made. This is a known, easily identified landmark that is very important when repositioning a two-sided flap. The remainder of the horizontal or envelope portion of the incision is then closed, after which the vertical component is closed.

Tension-free flap closure is a prerequisite to suturing. It is crucial that the edges of the flap come together passively. Significant force should not be required or used to bring the wound edges together. If the edges of the flap do not meet, or cannot be brought together easily without tension, the flap will require mobilization with a horizontal periosteal releasing incision. This incision is usually made at the base of the flap apical to the mucogingival junction. This incision makes the flap more elastic so that it can be mobilized coronally without tension. This allows passive closure of the flap. Periosteal release must be performed carefully to avoid perforating the flap. This technique is demonstrated in the ITI Academy Learning Module 'Periosteal Releasing Incision'.

There are additional considerations that promote uneventful healing and prevent complications. Flaps should always be repositioned over healthy bone. It is also important to avoid flap closure over rough bone or sharp bony edges. Smoothing down rough edges and areas of sharp bone will reduce the risk of wound breakdown and dehiscence. The edges of the flap must be handled in a gentle manner to avoid traumatizing the soft tissues. Even very careful suturing will not be able to improve the outcome if frayed flap edges have been created either due to forceful reflection of the flap or improper handling of the edges with tissue forceps.

General Principles of Surgical Flap Closure, Key Learning Points: Flaps should be closed so that the wound edges approximate; this promotes healing by primary intention. Healing by secondary intention is slower and may result in scar formation. Flap closure should begin with repositioning and suturing of key landmarks. Flap edges should come together passively to achieve stable, tension-free closure. Flap edges must be handled in an atraumatic manner.

It is well-documented that extraction of a tooth results in significant resorption of the alveolar process, leading to a reduction in the dimensions of the alveolar ridge. This knowledge underscores the importance of minimally traumatic extraction of the tooth that preserves the alveolar socket walls to facilitate subsequent implant placement. The trauma to the alveolus and soft tissue can be minimized if the clinician avoids buccolingual expansion of the alveolus and also avoids removing bone by means of an aggressive extraction technique. In addition, the resorption of the bone that occurs subsequent to reflection of the periosteum can be minimized by avoiding elevation of a flap.

However, there may be situations in which it is necessary to elevate a flap. One such situation is extraction of a tooth with significant destruction due to caries or resorption. Other examples are extraction of an unfavorably fractured tooth with limited visibility of the remaining tooth structure and extraction of a tooth with a root deformity. A flap must also be elevated when an oroantral communication to the maxillary sinus has been detected, because this situation very often requires primary closure of the extraction site.

The design of a flap elevated for tooth extraction depends on the particular clinical situation and should ensure that the extraction can be performed as atraumatically as possible with adequate visibility and access to the surgical area. A horizontal (or envelope) flap is created with an incision along the buccal aspect of the tooth or teeth in question, including the papillae on each side of the tooth or teeth. If a larger overview of the tooth is necessary, a two-sided flap may be elevated with a horizontal incision and one vertical releasing incision. If closure of a communication to the maxillary sinus is expected, a three-sided flap with two vertical releasing incisions should be elevated.

After the tooth has been extracted or surgically removed, several steps must be accomplished before flap closure can commence. Debridement of the area must be performed. Granulation tissue must be removed together with small bone particles. The area must be irrigated with sterile saline to remove bone debris and coagulated blood. If the buccal bone plate has been displaced during the removal of the tooth, it must be carefully replaced in the correct position. The buccal bone plate must not be forced into the extraction socket, because the buccal bone is needed for future implant placement. The flap must then be passively repositioned before suturing can be performed. In general, care should be taken never to remove a supposed excess of soft tissue. The soft tissue will heal but by secondary intention which may lead to scarring.

The horizontal flap is commonly sutured by interrupted, single sutures, one at each papilla. The buccal and the palatal or lingual papillae are brought together as shown, but they may not necessarily be in contact. The sutures function to stabilize the papillae and thereby promote healing. It is important to avoid too much pressure by the sutures because this will result in shrinkage of the papillae.

Other suture techniques may be used after tooth extraction. One such technique, the figure-of-eight suture, may provide a barrier to blood clot displacement. However, it is important to note that suturing across an open wound socket should not be relied upon to maintain the blood clot in the socket. Nevertheless, the figure-of-eight suture is useful in securing a hemostatic dressing. It may also be beneficial in securing grafting material placed during a ridge preservation procedure.

In addition to the figure-of-eight suture, two other techniques that may be used are the criss-cross and hidden criss-cross sutures. All three suture techniques compress the soft tissue margins. Care must be taken not to strangulate the tissue. Compression of the marginal soft tissue may result in a compromised esthetic result around a subsequently placed implant. A horizontal mattress suture or a crossed horizontal mattress suture can also be used but must be supplemented with single interrupted sutures at each papilla. As in the other techniques presented here, there is the possibility of damaging the soft tissue if the knots are tightened too tightly.

Closure of a two-sided flap elevated for tooth extraction follows the same sequence presented in the first Learning Objective. After passively repositioning the flap, suturing begins at the occlusal (or papilla) end of the vertical releasing incision. Thereafter, the papillae are sutured starting with the papilla closest to the vertical incision, and ending with the papilla farthest away from the vertical incision. The remainder of the vertical releasing incision is sutured to finalize the flap closure. Starting the suturing procedure at the wrong end of an incision may place too much pressure on the sutures. This can result in ruptured sutures or displacement of the mucogingival junction and an unsatisfactory esthetic result.

When an oroantral communication to the maxillary sinus has been detected following an extraction, the requirement for primary closure of the site depends on the size of the perforation of the sinus. Small communications with an opening of 1 to 2 millimeters may be treated by establishing a blood clot in the extraction site. The blood clot can be protected by a figure-of-eight suture or a horizontal mattress suture. Any vertical releasing incisions should be closed with single sutures. The patient must be instructed in nasal precautions (such as not blowing the nose) for up to 14 days and must be monitored postoperatively at recall appointments.

If a larger sinus perforation occurs, it may be necessary to achieve complete coverage of the extraction site with primary closure of a three-sided flap. A broad-based buccal three-sided flap is raised, and then a periosteal releasing incision is performed so that the flap can be advanced to the palatal aspect of the alveolar socket. The clinician must be able to position the flap free of tension. It may be necessary to remove some of the buccal bone wall to ensure a tension-free flap.

The suturing starts at the palatal aspect of the flap. Horizontal mattress sutures are helpful in everting the wound edges. The horizontal mattress sutures are supplemented by single interrupted sutures. The buccal vertical releasing incisions are then sutured by single interrupted sutures. Again, the patient must be instructed in nasal precautions for up to 14 days, and the patient must be monitored postoperatively at recall appointments. The sutures may be removed after 14 days. It should be emphasized that the primary closure of an oroantral communication will lead to a coronal displacement of the mucogingival junction and an unsatisfactory esthetic result. Moreover, a sinus floor elevation procedure will usually be required before an implant can be placed in the area. If part of the buccal bone wall was removed during the procedure, combined horizontal and vertical bone augmentation may be needed.

Flap Closure Following Extractions, Key Learning Points: Some extractions require elevation of a horizontal, two-sided, or three-sided flap to ensure adequate visibility and access to the site. Debridement, irrigation, and passive repositioning of the soft tissue are prerequisites for flap closure following extraction. Horizontal flaps are often closed with single sutures at the papillae; other techniques such as the figure-of-eight suture can be used to help maintain the blood clot in the socket. Failure to follow the correct sequence when suturing two- and three-sided flaps may result in an unsatisfactory esthetic outcome. Small sinus perforations may be managed by a figure-of-eight suture, whereas in case of a large sinus perforation a three-sided flap must be elevated and primary full-coverage closure must be performed.

In situations where assessment and planning show that there is adequate bone volume available to allow placement of implants without the need for augmentation, flapless surgical approaches can be employed. However, elevation of a surgical flap may be indicated to better visualize the implant site during placement. When available bone is limited, flap elevation can reduce the risk of bone fenestrations. Flap elevation is required when there is a need for localized bone augmentation to allow implant placement in the correct prosthodontically determined position. Elevation of a surgical flap can also aid in identifying and avoiding important anatomical landmarks, and thereby reducing the risk of complications.

In a one-stage surgical protocol, a one-piece implant and healing cap are placed, and the mucoperiosteal flaps are sutured to allow transmucosal healing. This protocol can also be used when a two-piece implant and a healing abutment are placed. The healing abutment or cap is not covered by the flap and remains exposed in the mouth throughout the healing period.

The flap is carefully and atraumatically repositioned around the healing cap or healing abutment and supported by sutures on the mesial and distal aspects. Sutures are placed from the buccal towards the lingual or palatal flap and tied so that the knots are positioned at the buccal aspect. If any vertical relieving incisions are present, these should be closed as normal to allow primary healing. It is important to note that in some situations the flap edges must be modified to achieve closure around a healing cap or abutment. For example, the edge of a palatal flap may need to be trimmed to create a "curve" that can adapt around the healing abutment.

In a two-stage surgical protocol, the implant and cover screw or short healing cap are placed, and the mucoperiosteal flaps are sutured with primary closure to achieve complete coverage of the surgical site. During healing, the implant and its cover screw or healing cap remain fully submerged under the mucoperiosteal flap. Following the healing phase, a second surgical procedure is carried out to expose the implant, remove the cover screw or healing cap, and place an appropriate abutment.

When an implant site requires simultaneous localized bone augmentation at the time of implant placement, a two-stage protocol is carried out with primary wound closure for submerged healing. The full mucosal coverage protects both the implant and the bone augmentation material against bacterial contamination. Following insertion of the implant and placement of a cover screw, local augmentation is performed with a bone substitute and membrane. A periosteal releasing incision is made to mobilize the flap in order to accommodate the augmentation material and to achieve tension-free primary closure. After a period of healing the implant is exposed again in a second surgical procedure to remove the cover screw and place the healing abutment.

Bone augmentation with a bone block is necessary when it is not possible to place the implant in the correct three-dimensional position due to lack of bone. Before closure of the wound, care should taken to ensure that the bone block is fixated to the underlying host bone and is not movable. A movable bone block will mimic a foreign body, which may result in inflammation, granulation, infection, potential scarring, and treatment failure. To obtain a tension-free flap and primary closure over the bone block, a periosteal releasing incision or incisions must be made. The periosteal releasing incision will result in bleeding in the surgical area. Care must be taken to ensure hemostasis before suturing is performed. Ongoing bleeding will result in rupture of the sutures. Following a period of healing, further surgery is carried out to remove potentially nonresorbable membranes and bone graft fixation screws and to place the implants into the augmented site.

The SAC classification categorizes cases as Straightforward, Advanced, or Complex. Cases involving the esthetic zone are classified as Advanced or Complex. Just as great care must be taken with flap design and flap mobilization in this region, as much care must be taken with flap closure. Damage to papillae from suturing can result in scarring, recession, and a compromised esthetic outcome. In this clinical example the upper right central incisor is being replaced with an implant and simultaneous bone augmentation. The flap has been repositioned in the correct anatomical position starting with the first suture at point 1. Note that the marginal gingival border at the right lateral incisor is in the correct position with no steps or abrupt uneven areas. The midline papilla is closed by a vertical mattress suture. Note that the wound edges of the midline papilla are approximated and there is no potentially damaging pressure on the papilla itself. Due to the simultaneous bone augmentation procedure a single horizontal mattress suture supports the single interrupted sutures in closure of the flap. A 5-0 chromic gut suture has been used. In general, a nonresorbable 5-0 or finer monofilament suture is recommended in the esthetic zone. Details regarding different suture types are outlined in the ITI Academy Learning Module 'Suturing Materials and Techniques'.

Flap Closure for Implant Surgery, Key Learning Points: Flaps must be repositioned neatly and atraumatically around healing abutments in transmucosal healing protocols in which the abutment remains exposed in the oral cavity. Primary closure and submerged healing are required for two-stage implant placement, with or without simultaneous local bone augmentation. Primary closure is required for staged block bone grafting. Good flap mobilization is necessary to accommodate the space required for augmentation materials and to achieve tension-free closure. Great care must be taken when closing flaps in the esthetic zone; 5-0 or finer monofilament sutures are recommended.

The aim of suturing is to close the wound in a manner that reduces bacterial entry, encourages proper healing, and produces the least possible scarring. Complications may arise if there is an absence of careful treatment planning, lack of primary closure, or incorrect suture technique. Complications resulting from flap closure may be immediate or delayed. Immediate complications include the formation of a hematoma secondary to insufficient hemostasis and the development of wound infection. Delayed complications include wound dehiscence and wound necrosis leading to a possible loss of bone augmentation material and in some situations failure of the treatment. Other delayed complications are scar formation and persistent stitch marks, which in the esthetic zone may compromise the success of treatment.

A wound dehiscence is defined as an incomplete wound healing in which the wound edges open up again following closure by suturing. Both local and systemic factors can contribute to the occurrence of dehiscence. A primary local factor is too much tension in the flap. Other causes are insufficient blood supply, excessive postsurgical edema, or compromised healing.

Other general or systemic factors influence wound healing and thereby also influence the formation of wound dehiscences. Aging causes changes in the oral mucosa, with a general thinning of tissues. As a result, in the elderly wound edges can be thinner and more friable. In addition, older patients' circulation may be impaired, which can affect healing. The patient's medical status, especially the use of medication such as steroids or immunosuppressive drugs, can adversely affect healing and increase susceptibility to infection. Patient habits, especially smoking, can have a negative effect on healing. Smoking constricts the arterioles that supply the tissues with the oxygen that is needed for healing. Patient compliance with postsurgical instructions is another key factor affecting the incidence of dehiscences. A prerequisite for successful healing is the patient's adherence to oral hygiene instructions after surgery. Lack of oral hygiene will result in inflammation of the soft tissue as well as possible infection of the treatment site leading to rupture of the sutures and formation of a wound dehiscence.

The signs and symptoms of wound dehiscence are rupture of the sutures and swelling of the mucosa with opening of the wound. There will be inflammation and, in some situations, infection. If there is infection the patient will most often complain of pain. Small dehiscences may be covered by fibrin. Large dehiscences may result in exposure of bone augmentation materials, membranes, or even the implant surface.

Wound dehiscences require action. First, the surgeon must decide if the implant treatment should be regarded as a failure or not. If the dehiscence is small, with a surface covered by fibrin, the recommended treatment is to clean the area and to instruct the patient in thorough oral hygiene, after which the patient must be followed up until complete healing is obtained. In case of a large dehiscence with loss of bone augmentation or membrane materials, exposure of the implant surface, or visible necrotic bone, the treatment should be considered a failure. The implant must be removed and the area debrided and re-sutured. After a healing period, re-treatment can be considered.

Complications, Key Learning Points: Poor planning, improper technique, and lack of primary closure can result in immediate or delayed complications. Wound dehiscence can occur as a result of too much tension in the flap or failure to achieve primary closure. Smaller wound dehiscences can be treated. Large wound dehiscences that expose augmentation materials or the implant surface can result in failure of implant treatment.

Flap Closure, Module Summary: Flap closure should promote healing by primary intention through close approximation of wound edges, lack of tension in the flap, and correct suturing sequence. Flaps elevated for tooth extraction must be passively repositioned prior to closure and sutured in the correct sequence. Oroantral communications with the maxillary sinus require flap elevation; larger sinus perforations require a periosteal releasing incision and primary closure. Transmucosal implant healing protocols require close adaptation of flaps around healing abutments. Submerged implant healing protocols and grafting with block bone require primary flap closure. Flaps for implant placement in the esthetic zone should be closed with 5-0 or finer monofilament sutures. Too much tension in the flap or failure to achieve primary closure can result in wound dehiscence, compromised esthetics, or failure of treatment.