Background: Guided bone regeneration (GBR) is an established and predictable procedure used to obtain adequate alveolar bone for the placement of dental implants. Anatomical challenges, such as the proximity of the maxillary sinus, may lead to complications during a GBR procedure. The purpose of this report is to present a unique and hitherto unreported complication of a GBR procedure, i.e., the penetration of a titanium fixation tack into the maxillary sinus.
Case Report: A unique GBR is presented, where a titanium tack penetrated the maxillary sinus with subsequent migration and loss. Attempts to locate the tack visually during the procedure were unsuccessful. The GBR procedure was aborted and dental radiographs were immediately obtained. The patient was completely asymptomatic during the healing period. Eight weeks later a cone beam computed tomography revealed a non-inflamed sinus with no pathology evident. However, the tack could not be visualized. An otolaryngology consultation was requested and the ensuing sinus endoscopy did not reveal any evidence of the penetrated tack. It is thought that the loose tack migrated completely out of the sinus through the nasal passage.
Conclusions: The use of a pre-operative cone beam computed tomography (CBCT) would have allowed the clinician to assess the exact thickness of the lateral wall of the maxillary sinus and better determine the ideal placement location and/or the feasibility of using a fixation tack in the posterior upper jaw.

Keywords: Maxillary Sinus, complication, guided bone regeneration, titanium tack