Background: Membrane exposure has been associated with poor clinical outcomes in guided bone regeneration. This prospective human study examined the effect of incision locations on flap survival and membrane exposure.
Methods: Twenty-nine implant-associated buccal dehiscence defects in 25 patients were augmented using particulate mineralized human allograft. Ten sites received a collagen bioabsorbable membrane, 10 sites received acellular dermal matrix, and nine sites were treated with bone graft alone. All implants achieved primary stability and passive flap tension at the time of flap closure. Incision location was measured as the distance from the initial incision line to the mucogingival junction. The same measurements were made at 2 weeks and 1 month to represent the length of the flap that survived. The length of the flap that survived at 2 weeks was compared to the mean width of buccal keratinized gingiva (KG) of adjacent teeth. Other clinical parameters recorded included incidence of early membrane exposure and gingival thickness at mid-crest and 6 mm buccal and lingual to the mid-crest at baseline.
Results: At 2 weeks, 10 sites experienced early exposure. Exposed sites that were not covered by 1 month remained exposed. Membrane-treated groups showed no significant difference between the width of adjacent buccal KG and the length of the flap that survived at 2 weeks. The length of the flap that survived beyond the mean width of adjacent KG was significantly greater for the graft alone group (1.6 +/- 0.4 mm; P = 0.002). When the gingival thicknesses of exposed and non-exposed cases were compared, only palatal/lingual gingival thickness showed a significant difference (P = 0.002).
Conclusions: Within the limits of the study, it was concluded that the location of the crestal incision might be a significant factor in reducing the incidence of membrane exposure by minimizing flap necrosis. The mean KG width of adjacent teeth may be used as a guide to determine the initial incision location. However, this effect may be less significant in palatal/lingual gingiva >3.0 mm.