**6. Odontogenic sinusitis**

Odontogenic sinusitis should be suspected when maxillary sinusitis does not heal [14, 15]. This is especially in the case of unilateral CRS (**Figure 10a** and **b**), but odontogenic infection may also be the source of bilateral CRS. Before referring to FESS, due to maxillary sinus opacification, odontogenic maxillary sinusitis must be ruled out. FESS in odontogenic cases may induce more inflammation and osteitis [1]. Odontogenic sinusitis and sinonasal complications of dental disease or treatment represent a heterogeneous group of conditions that often require multidisciplinary care [17].

**Figure 10.**

*(a) Coronal CT and (b) axial CT reveal periapical lucency around a molar tooth [16] consistent with odontogenic infection as the cause of sinusitis. The sclerotic maxillary sinus walls indicate a long-standing infection.*
