Vascularized Connective Tissue Flap for Bone Graft Coverage

Vertical and/or horizontal alveolar defects are often associated with missing bone and mucosa. Many techniques are available for reconstructing these areas, including both hard- and soft-tissue procedures.1 Bone grafts reliably restore the alveolar ridge but do not address deficient keratinized mucosa.

Implant placement in prosthetically accurate positions, especially when alveolar ridge augmentation procedures are performed, often result in emergence of abutments through nonkeratinized and unattached mucosa. It is necessary to widely undermine the flap to achieve primary closure over the bone graft to avoid placing tension over the graft. Excess tension can cause dehiscence and exposure of the graft, which may lead to significant resorption or loss of the graft. Undermining of the flap can lead to loss of vestibular height and restricted movement of the lip. This flap advancement recruits nonkeratinized mucosa to cover the graft.

Currently, it is widely accepted that keratinized mucosa, although not essential to the existence of a tooth and its attachment apparatus, does enhance the long-term survival of the tooth. On review of the literature, it is evident that the presence of the keratinized mucosa is especially important around restorations and prostheses or if the tooth is in a dentition susceptible to periodontal breakdown.2–5 However, there has been considerable discussion as to whether the extent of keratinized gingiva adjacent to implants bears the same significance as to natural teeth.6–9 The structure and function of the mucosa that surrounds implants have been examined,10 and it was observed that the soft-tissue response to plaque develops in a similar manner around teeth and dental implants.11,12 Longitudinal studies definitively establish that although patient comfort may be enhanced in selected patients with the presence of keratinized gingiva around implants, its presence is not necessary for establishment of osseointegration or for its long-term maintenance.13 

Although controversy exists regarding the need for attached mucosa surrounding osseointegrated implants, there are many benefits.10,14–17 In the anterior maxilla, optimal esthetics dictate the need for keratinized tissue in the peri-implant region. Flap procedures and grafting techniques have been described to increase the zone of attached mucosa.18–27 

The purpose of this study is to describe a split-thickness flap technique that increases the amount of keratinized tissue in conjunction with bone augmentation and implant placement, thus providing optimal anterior esthetics.

This study comprised 17 patients with insufficient hard and soft tissue involving the anterior maxilla. There were 10 vertical (height) bony defects and 7 horizontal (width) defects. All defects were grafted with autogenous bone. The harvest sites included the iliac crest (vertical defects; n  =  10) and lateral ramus (horizontal defects; n  =  7). The size of the graft was related to the bone defect. The graft ranged in width between 5 cm³ and 30 cm³.

A split-thickness flap technique was used primarily at the time of grafting in 9 patients and secondarily when exposing the graft in 8 patients. Rootform implants were placed simultaneously with the graft procedure in 5 patients and secondarily in 11 patients. A total of 41 osseointegrated implants were placed in the anterior maxilla. A subjective esthetic evaluation of the area included evaluating the shape, color, form, and sufficiency of the reconstruction.

A partial-thickness incision (Figure 1) is made with a 15 surgical blade and placed in the keratinized mucosa approximately 3 mm from the mucogingival junction. A beaver blade is then used to undermine the palatal tissue. The amount of undermining depends on the desired amount of keratinized tissue to be gained and the need for sufficient coverage of the graft. The palatal tissue is retracted, and a 15 blade is then used to incise the tissue to bone. At this point, the connective tissue flap is reflected in a subperiosteal manner. The alveolar defect is exposed and grafted with either a block onlay graft or a particulate graft with a membrane. Implants may be placed at the time of grafting or at a second stage. The split-thickness flap is then positioned apically to cover the graft and sutured to the palatal flap. A minimum 3-mm overlap of the 2 flaps was needed to avoid tissue breakdown at the junction, essential for reestablishment of vascularity. An area of exposed connective tissue is visible over the reconstructed ridge and is left to epithelialize (Figure 2).

The development of the split-thickness flap (Figure 3) is made in the same manner as for the stage I technique. The graft is exposed, and the entire flap is repositioned apically and secured into place. The exposed connective tissue is left to epithelialize with attached mucosa (Figure 4).

The postoperative course was uneventful for all patients. There were no patients with dehiscence or necrosis of the flap. Two patients complained of slight pain involving the harvest site for the bone graft. The split-thickness portion of the flap was epithelialized with keratinized tissue by the third week. There was also an increase in vestibular depth that was not quantified.

Postoperative inconveniences were minimal, with postoperative bleeding and discomfort only occasional complications. Hard- and soft-tissue anatomy was considered acceptable, and additional bone augmentation procedures were not performed. Proper functional and esthetic restorations could be prepared for all implants 3 weeks after the surgery (Figures 5 and 6).

Bone grafting and osseointegrated implants have shown to be a predictable method for restoring both form and function.1 Unfortunately, the soft-tissue deficiency is not addressed with this procedure and may actually be adversely affected by undermining and disrupting the adjacent anatomy.

Although keratinized tissue is not indispensable for maintenance of peri-implant tissue health, its presence has many benefits. Keratinized tissue enhances esthetics and is associated with less gingival recession, easier plaque control, and protection from bacterial aggression.10,16 Proper soft-tissue anatomy around implants provides a healthy soft-tissue barrier, which facilitates oral hygiene and gives the prosthetic restoration a more natural look.18 Block and Kent19 have shown a correlation between the presence of keratinized mucosa and the health of soft and hard tissues around implants.

After second-stage surgery, the zone of keratinized tissue is frequently inadequate. Classical uncovering incisions and flap designs often result in compromised esthetic soft tissue.20 From a clinical standpoint, oral hygiene techniques are easier to perform and more comfortable for the patient when an adequate zone of attached gingival is present.

Grafts and membranes should be completely covered and remain submerged during the entire healing period. Tension-free closure is important for the success of the bone-grafting procedure. Undermining and advancement may lead to extreme displacement of the mucogingival border and disruption of the entire soft-tissue architecture.21 An advantage to using the split-thickness flap that we describe at the time of bone grafting (primary) is that it avoids a decrease in the vestibule caused from extensive undermining of the buccal mucosa and lip to achieve primary closure. This technique allows simultaneous placement of the bone graft and implants, greatly reducing total treatment time. It can be combined with guided bone regeneration procedures using particulate bone grafts as well as block onlay grafts.

Many surgical techniques have been described to create or increase the zone of keratinized tissue around osseointegrated implants, including rotated palatal flaps,14,17,22 various autografts,23–35 and coronally positioned palatal sliding flaps.14 Landi and Sabatucci26 recently described a modified technique for uncovering implants at the time of membrane removal, which can lead to an increased amount of keratinized tissue.26 Saadoun and Le Gall27 described an apical repositioned full-thickness flap procedure, which leaves subsequent bone denudation. Denuded bone not only becomes susceptible to resorption, infection, and mechanical irritation but also causes greater postoperative pain than tissue-covered bone.36,37 Histologic studies have demonstrated that exposed bone results in significant bone resorption.38,39 In 1992, Scharf and Tarnow32 described a modified roll technique for localized ridge augmentation. Their technique involved creating a trapdoor by preserving a partial-thickness flap overlying the area of connective tissue harvest. The technique that we describe is similar with the exception that the connective tissue portion of the flap remains exposed and is allowed to epithelialize rather than rolled beneath the flap. This technique minimizes the amount of exposed bone.

Moreover, likewise, Zigdon and Machtei40 investigated the association between the dimensions of keratinized mucosa with clinical and immunological parameters around dental implants. It was observed that a thick mucosa (≥1 mm) was associated with lesser buccal mucosal recession compared with a thin mucosa (<1 mm). These findings are of special importance in the esthetic zone, where narrow and thin keratinized mucosa may lead to greater mucosal recession.40 

The split-thickness flap procedure augments the buccal peri-implant keratinized tissue while avoiding a large zone of exposed bone. This provides improved bone protection with acceleration of wound healing and minimizes the danger of infection. Split-thickness flap procedures are less traumatic than full-thickness flap surgery.38 

Split-thickness flaps are broad based, which maintains their blood supply. This flap avoids a donor site, which differs from free connective tissue and gingival grafts.41,42 Leaving connective tissue denuded elicits keratinized tissue formation.26 As the flap becomes epithelialized, it blends with the surrounding keratinized tissue.

This technique is simple and predictable and consistently provides a wider zone of keratinized gingiva in the buccal aspect of the future maxillary implant–supported restoration. This is especially important in the anterior maxilla, where esthetics is of paramount importance.

Apical repositioning of a split-thickness flap combined with bone grafting and implants restores both form and function with optimal esthetics. This technique addresses both hard- and soft-tissue deficiencies and may eliminate the need for further soft-tissue grafting. It also avoids disruption of the adjacent facial soft-tissue anatomy and can be performed primarily with the bone-grafting procedure.