A Combined Bilaminar Tunnel Technique Using a Volume-Stable Collagen Matrix for Root Coverage in Anatomically Complex Sites: Technique Description and Report of Two Cases

The technical report described a novel treatment protocol for multiple recessions with anatomy- driven complexity from pre-operative evaluation, flap preparation, and the combination use of grafting materials. Clinical examination and cone-beam computed tomography were used to perform the comprehensive assessment before surgery. During surgical approach, sequentially combined bilaminar tunnel technique(cTUN) was performed. Firstly, tunneled coronally advanced flap (tCAF) was made at the most severe tooth sites, and the combination of modified tunnel technique with modified tunnel and vestibular incision subperiosteal tunnel access (mVISTA) was used to bypass the anatomic obstacles from two directions. Lastly, the de-epithelialized free gingival graft (DCTG) was sutured at coronal part for gingival recession coverage, and the volume-stable collagen matrix (VSCM) was placed at apical partially thickness flap to fill the concavities. When high complexity with anatomic difficulties was determined, the cTUN technique, combined tCAF and mVISTA approaches, effectively led to the preservation of flap integrity during flap preparation, favorable clinical outcomes of root coverage, and the stability of soft tissue at 6-month follow-up based on the reported cases.