Odontogenic sinusitis (ODS) is distinct pathophysiologically from nonodontogenic rhinosinusitis. ODS refers to bacterial sinusitis secondary to infectious dental pathology or procedures. Sinus mucosal inflammation in ODS is severe, mostly lymphocytic, and is driven by Th1 or Th17 inflammation. The sinus’s respiratory mucosa maintains its structure and function, contrary to significant epithelial barrier dysfunction seen in some forms of chronic rhinosinusitis. The severe inflammation and infection of ODS help explain certain unique clinical features like foul-smelling drainage, frequent purulence, and papillary edema on nasal endoscopy. Appreciating the unique pathophysiology of ODS facilitates its recognition and selection of optimal interventions.