The etiopathophysiology of odontogenic maxillary sinusitis has changed over time. Untreated dental diseases (e.g., dental caries) causing odontogenic maxillary sinusitis have become rare. Instead, most teeth which cause odontogenic maxillary sinusitis have already received dental treatment, especially root canal treatment, that is, endodontics. Consequently, it is very important that the teeth always be suspected as the cause of odontogenic maxillary sinusitis, even if a dental procedure has already been performed.

In the diagnosis of odontogenic maxillary sinusitis, it is important to detect the relationship between endodontic and periodontic lesions, including evidence of periapical lesions and the maxillary sinus.

Cone-beam CT, in addition to physical examination, is extremely accurate and useful for the diagnosis of odontogenic maxillary sinusitis. Plain dental radiography frequently fails to detect maxillary dental infections that could cause odontogenic maxillary sinusitis. The relationship between the causative teeth (endodontic and periodontic lesions, including evidence of periapical lucencies) and the maxillary sinus can be accurately observed and odontogenic maxillary sinusitis can be accurately diagnosed using cone-beam CT. In addition to accurate diagnosis of apical lesions, the maxilla, maxillary sinus, periodontal ligament space, lamina dura, pulp cavity, root canal and canal-treated roots, as well as apical periodontitis, alveolar ostitis and marginal periodontitis of the causative teeth can be observed. Metal artifacts are minimized, making cone-beam CT useful for diagnosis of the periodontal tissue condition and identification of the causative teeth, including root-canal-treated and crown-restored teeth.