When I teach extraction techniques, closure of extraction sites is frequently raised as a concern. Veterinarians often tell me they find it challenging to recruit enough tissue to close certain sites with a flap, such as the maxillary and mandibular canine teeth. One of the most important concepts I learned during my residency was how to raise mucoperiosteal flaps. Whether it is for closure of an extraction site, a large oronasal fistula, a radical maxillectomy closure, or a large congenital cleft palate, there is almost always a method to achieve primary closure. Where it seems like it would be impossible to close a defect, with patience, care, and knowledge of some basic tenets, we can achieve primary closure.
Pushing the envelope
Mucoperiosteal flaps are an important part of every oral surgery. The most basic form of flap is the envelope flap (Figure 1), which refers to an intrasulcular incision that releases the gingiva and mucosa without a vertical incision. When used for extraction, the envelope is often continued around the circumference of the tooth to be extracted. The envelope flap provides the least amount of visualization and tissue for closure, but it is sufficient for extraction of single-rooted teeth, such as incisors and first premolar teeth.
A triangle flap provides better exposure to the bone and increased tissue for tension-free closure. This involves the incorporation of a releasing incision in addition to the envelope flap. A good indication for a triangle flap is for extraction of a two-rooted tooth, where one root shows radiographic evidence of periodontal bone loss and the other shows none. In this case, the releasing incision should be done at which root? Since more exposure will be needed to remove bone from the buccal surface of the more firmly rooted tooth, the releasing incision would be placed at the root that is less affected by periodontal bone loss.
A full-thickness pedicle flap provides the most exposure to a tooth that requires extraction, and is, therefore, a good choice when extracting firmly rooted teeth, such as a carnassial tooth or a maxillary or mandibular canine tooth. Similarly, a pedicle flap provides the best chance for tension-free closure, and is often necessary when the defect is very large (Figure 2).
Regardless of the type of flap chosen, there are important surgical principles that should be adhered to whenever a mucoperiosteal flap is utilized. First, avoid handling the flap’s edges excessively to minimize effects on blood supply and flap vitality. When raising a flap to close an existing defect, the flap should be larger than the defect. Use large flaps to cover small defects, and use even larger flaps to cover large defects. When raising a pedicle flap for an extraction, utilizing broad-based flaps may improve blood supply to the distal portion of the flap. When parallel vertical releasing incisions are used, the flap tends to curl and seemingly shrink, making tension-free closure more difficult. Avoid perforation of the flap when raising it by using a sharp periosteal elevator directed toward the bone. If the flap is going to perforate anywhere, it will usually occur at the mucogingival line, since this is the thinnest part of the flap.
Cutting the tension with scissors
One of the most important tenets of flap surgery is achieving a tension-free closure. To minimize tension on a mucoperiosteal flap, a release of the periosteum can be done either via blunt or sharp dissection, apical to the mucogingival line. The periosteum is a translucent membrane that is best identified at the most apical portion of a releasing incision by placing a pair of iris scissors, tenotomy scissors, or small Metzenbaums into the space between the mucosa and submucosal structures. Opening of the scissors’ closed jaws allows for separation and identification of the periosteum for additional blunt or sharp dissection. The periosteal release creates a noticeable degree of relaxation, effectively doubling the amount of distance the pedicle flap can travel before it feels tension again. After releasing the periosteum, I lay the flap over the defect to see if it recoils. If not, that’s a good sign tension has been relieved and you are ready to close.
Regarding suture patterns, when in doubt, utilize closely spaced (approximately 3 mm apart) simple interrupted sutures with absorbable monofilament. Whenever possible, it is ideal to avoid placing sutures directly over a void, as lack of support for the flap will likely increase tension when pressure is placed on the flap. Sometimes, a two-layer closure is possible, the first layer often incorporating submucosal mattress sutures. In cases where dehiscence is likely, holes can be drilled into the bone and submucosal bites of tissue can be tacked down to the bone. Allograft membranes may be used to provide support beneath a mucoperiosteal flap.
Hopefully, these tips will help you when raising your next mucocutaneous flap in a dog. Principles are similar for cats, though finesse really comes into play, given their paper-thin mucosa. Good technique and proper equipment allows for success.
John Lewis, VMD, FAVD, DAVDC, practices dentistry and oral surgery at Veterinary Dentistry Specialists and is the founder of Silo Academy Education Center, both located in Chadds Ford, Pa.