Spontaneous Bone Formation on the Maxillary Sinus Floor in Association with Surgery to Remove a Migrated Dental Implant: a Case Report

Aim: A variety of surgical techniques have been developed to reconstruct the posterior maxilla when bone volume is insufficient. For some decades, sinus augmentation, using various bone substitutes, has been used to reconstruct the posterior maxilla for dental implant placement. Even if new bone formation is achieved in the sinus after bone grafting, the possibility of new bone formation with only a membrane elevation in the maxillary sinus has been reported in human and animal studies. The aim of this case report was to document an unexpected healing pattern after the removal of a dental implant migrated in the maxillary sinus.

Methods: In October 2009 a 49-year-old man with a partially edentulous maxilla underwent implant placement. Specifically, a total of 5 implants were inserted, 2 in the left and 3 in the right posterior maxilla. Four months later, at the time of abutment connection, the implant at the site of the maxillary left first molar was accidentally pushed in the sinus. A surgical removal of the implant from the maxillary sinus was proposed and the patient consented to the surgical intervention. Computed axial tomography (CAT) scan images revealed opacification of the left maxillary sinus with mucosal thickening, and the dental implant displaced within the sinus. The planned treatment sequence was: 1) removal of the implant; 2) sinus augmentation procedure after 5 months; 3) implant insertion 5 months after the bone graft. The implant was removed. Five months later, the patient was admitted for the bone-grafting augmentation procedure. A new CAT scan image revealed normal mucosal thickness and no opacification of the left maxillary sinus; bone formation was evident. The surgery was undertaken with local anesthesia and conscious sedation.

Results: At reentry, the sinus wall was found to be totally healed. Newly formed bone (21.2%) with wide osteocyte lacunae and large marrow spaces (73.8%) were present with newly formed vessels and no inflammatory cell infiltrate.

Conclusion: The surgical trauma and the creation of a secluded space between the bone surfaces and the healed sinus mucosa resulted in a spontaneous bone formation in the maxillary sinus. The surgical approach described may be used to achieve bone formation to enable placement of dental implants without the addition of any grafting material.