A Dual-Layer Flap Preparation Approach Utilizing the External Coronally Advanced Flap and the Internal Trapdoor Periosteal Flap for Endodontic Microsurgery in the Esthetic Zone: Technique and Case Report.

Endodontic microsurgery (EMS) is often utilized to surgically treat teeth with persistent endodontic lesions when conventional nonsurgical endodontic treatments have been unsuccessful. However, EMS with conventional techniques may result in esthetic concerns, such as gingival recession, papilla loss, and soft tissue scarring, especially in patients with high esthetic demands. This manu-script describes a dual-layer flap preparation approach that utilizes an external coronally advanced flap (CAF) and an internal trapdoor periosteal flap (TPF) for EMS in the esthetic zone. The external CAF is a split-full-split-thickness flap that allows the gingival margin to be coronally advanced over the cementoenamel junction or prosthetic margin to mitigate any potential gingival recession due to flap retraction or to treat existing gingival recession. The internal TPF is the periosteal elevation of the partial-thickness tissue that remained after the elevation of the external CAF. The internal TPF employs vertical release(s) to obtain adequate access for periapical surgery. Sites treated with this approach healed with no complications, minimal patient discomfort, no facial recession or loss of papilla, and minimal soft tissue scarring. Therefore, the dual-layer flap preparation approach is suggested as a viable flap design for EMS in the esthetic zone.