A periodontal flap is a section of gingiva, mucosa, or both that is surgically separated from the underlying tissues to provide for the visibility of and access to the bone and root surface. The flap also allows the gingiva to be displaced to a different location in patients with mucogingival involvement.
In a full-thickness flap, all of the soft tissue, including the periosteum, is reflected to expose the underlying bone. This complete exposure of and access to the underlying bone is indicated when resective osseous surgery is contemplated.
The partial-thickness flap includes only the epithelium and a layer of the underlying connective tissue. The bone remains covered by a layer of connective tissue that includes the periosteum. This type of flap is also called the split-thickness flap. The partial-thickness flap is indicated when the flap is to be positioned apically or when the operator does not want to expose bone.
Conflicting data surround the advisability of uncovering the bone when this is not actually needed. When bone is stripped of its periosteum, a loss of marginal bone occurs, and this loss is prevented when the periosteum is left on the bone.4 Although this is usually not clinically significant,7 the differences may be significant in some cases (Figure 57-2). The partial-thickness flap may be necessary when the crestal bone margin is thin and exposed with an apically placed flap or when dehiscences or fenestrations are present. The periosteum left on the bone may also be used for suturing the flap when it is displaced apically.
For flap placement after surgery, flaps are classified as either (1) nondisplaced flaps, when the flap is returned and sutured in its original position, or (2) displaced flaps, which are placed apically, coronally, or laterally to their original position. Both full-thickness and partial-thickness flaps can also be displaced. However, to do so, the attached gingiva must be totally separated from the underlying bone, thereby enabling the unattached portion of the gingiva to be movable. Palatal flaps cannot be displaced because of the absence of unattached gingiva.
Apically displaced flaps have the important advantage of preserving the outer portion of the pocket wall and transforming it into attached gingiva. Therefore, these flaps accomplish the double objective of eliminating the pocket and increasing the width of the attached gingiva.
For the management of the papilla, flaps can be conventional or papilla preservation flaps. With the conventional flap, the interdental papilla is split beneath the contact point of the two approximating teeth to allow for the reflection of the buccal and lingual flaps. The incision is usually scalloped to maintain gingival morphology and to retain as much papilla as possible. The conventional flap is used (1) when the interdental spaces are too narrow, thereby precluding the possibility of preserving the papilla, and (2) when the flap is to be displaced.
Conventional flaps include the modified Widman flap, the undisplaced flap, the apically displaced flap, and the flap for reconstructive procedures. These techniques are described in detail in Chapter 59.
The papilla preservation flap incorporates the entire papilla in one of the flaps by means of crevicular interdental incisions to sever the connective tissue attachment as well as a horizontal incision at the base of the papilla to leave it connected to one of the flaps.
The design of the flap is dictated by the surgical judgment of the operator, and it may depend on the objectives of the procedure. The necessary degree of access to the underlying bone and root surfaces and the final position of the flap must be considered when designing the flap. The flap design may also be dictated by the aesthetic concerns of the area of surgery. Preservation of good blood supply to the flap is another important consideration.
For the conventional flap procedure, the incisions for the facial and the lingual or palatal flap reach the tip of the interdental papilla or its vicinity, thereby splitting the papilla into a facial half and a lingual or palatal half (Figures 57-3 and 57-4).
The entire surgical procedure should be planned in every detail before the procedure is initiated. This should include the type of flap, the exact location and type of incisions, the management of the underlying bone, and the final closure of the flap and sutures. Although some details may be modified during the actual performance of the procedure, detailed planning allows for a better clinical result.
Horizontal incisions are directed along the margin of the gingiva in a mesial or distal direction. Two types of horizontal incisions have been recommended: the internal bevel incision,6 which starts at a distance from the gingival margin and which is aimed at the bone crest, and the crevicular incision, which starts at the bottom of the pocket and which is directed to the bone margin. In addition, the interdental incision is performed after the flap is elevated to remove the interdental tissue.
The internal bevel incision is basic to most periodontal flap procedures. It is the incision from which the flap is reflected to expose the underlying bone and root. The internal bevel incision accomplishes three important objectives: (1) it removes the pocket lining; (2) it conserves the relatively uninvolved outer surface of the gingiva, which, if apically positioned, becomes attached gingiva; and (3) it produces a sharp, thin flap margin for adaptation to the bone–tooth junction. This incision has also been termed the first incision, because it is the initial incision for the reflection of a periodontal flap; it has also been called the reverse bevel incision, because its bevel is in reverse direction from that of the gingivectomy incision. The no. 15 or 15C surgical blade is used most often to make this incision. That portion of the gingiva left around the tooth contains the epithelium of the pocket lining and the adjacent granulomatous tissue. It is discarded after the crevicular (second) and interdental (third) incisions are performed (Figure 57-5).
The internal bevel incision starts from a designated area on the gingiva, and it is then directed to an area at or near the crest of the bone (Figure 57-6). The starting point on the gingiva is determined by whether the flap is apically displaced or not displaced (Figure 57-7).
The crevicular incision, which is also called the second incision, is made from the base of the pocket to the crest of the bone (Figure 57-8). This incision, together with the initial reverse bevel incision, forms a V-shaped wedge that ends at or near the crest of bone. This wedge of tissue contains most of the inflamed and granulomatous areas that constitute the lateral wall of the pocket as well as the junctional epithelium and the connective tissue fibers that still persist between the bottom of the pocket and the crest of the bone. The incision is carried around the entire tooth. The beak-shaped no. 12D blade is usually used for this incision.
A periosteal elevator is inserted into the initial internal bevel incision, and the flap is separated from the bone. The most apical end of the internal bevel incision is exposed and visible. With this access, the surgeon is able to make the third incision, which is also known as the interdental incision, to separate the collar of gingiva that is left around the tooth. The Orban knife is usually used for this incision. The incision is made not only around the facial and lingual radicular area but also interdentally, where it connects the facial and lingual segments to free the gingiva completely around the tooth (Figure 57-9; see Figure 57-5).