Abstract: PURPOSE: To present a functional surgery for odontogenic cysts intruding into maxillary sinus to preserve the sinus mucosa and alveolar bone, and plan the surgery with assistance of digital design and evaluate postoperative outcomes. METHODS: Patients with odontogenic cysts intruding into posterior part of maxillary sinus were collected from December 2011 to December 2014 Different operations were chosen according to volume and location of the lesion with assistance of digital operative design. Method Ⅰ"fenestration and bone reposition" was suitable for large lesion exceeding zygomatic alveolar ridge but without apparent bone destruction of anterior wall of the sinus, while method Ⅱ "bone removal" was applied for small lesion near zygomatic alveolar ridge. Evaluation of operation methods included anesthetic effect, bleeding, lesion removal difficulties according to operative design and operation time. The duration of pain and swelling, and the condition of free bony wall were assessed postoperatively. RESULTS: Fifteen cases adopted method Ⅰwhile 6 underwent method Ⅱ. Operations were completed in 20 minutes smoothly. Pain disappeared in 3.72 days on average, and swelling resolved in 7.67 days on average. Nasal bleeding occurred in 8 patients lasting 1 to 3 days. Suppurative inflammation was observed in 1 patient, and infection occurred after bone reposition. Other repositioned free bony wall were without resorption on CT images. CONCLUSIONS: Sinus mucosa and bony wall should be conserved. Preoperative digital design can guide osteotomy effectively during the surgery. Bone reposition is not suitable for suppurative inflammation.

Key words: Odontogenic maxillary sinus cystic lesions, Sinus mucosa preservation, Digital design, Bony window reposition, Piezosurgery