慢性的な口腔鼻腔瘻（OAF）から機能的なインプラントによる再建へ：シンフィシスブロック移植を用いた2段階再建の症例報告

Oroantral fistulas (OAFs), which often arise after posterior maxillary tooth extraction, may lead to chronic sinusitis and complicate future implant therapy if untreated. Their management depends on the defect size, sinus condition, and long-term prosthetic plan. This report presents a two-stage approach using initial sinus closure followed by mandibular symphysis block grafting and implant-supported rehabilitation.

A 63-year-old male patient presented with chronic OAF in the posterior left maxilla. Clinical and cone-beam computed tomography (CBCT) examinations revealed direct sinus exposure and infection. The first stage involved sinus decontamination and closure via a buccal sliding flap. Two months later, after mucosal healing, a cortico-cancellous block graft harvested from the mandibular symphysis was fixed to the defect with a titanium miniplate in combination with sinus lifting, a xenograft, and a collagen membrane. Four months post-grafting, CBCT confirmed adequate bone volume, enabling the placement of two implants. After osseointegration, a zirconia-based fixed prosthesis was delivered.

The staged protocol achieved predictable closure of the OAF, stable ridge augmentation, and successful implant placement at four months. At the two-year follow-up, the implants remained stable, with preserved marginal bone levels, healthy sinus function, and full prosthetic function. No donor site morbidity or sinus complications were observed.

This case illustrates that a two-stage protocol prioritizing sinus health followed by symphysis block reconstruction provides a reliable and biologically sound option for chronic OAFs with extensive bone loss, enabling predictable implant-supported rehabilitation.