Objective      To explore the ratio of odontogenic maxillary sinusitis (OMS) in maxillary sinusitis patients in dental clinic

the main causes

and the relationship between OMS and the roots of pathogenic tooth using cone beam computed tomography (CBCT).       Methods      Through analysis and measurement of 500 CBCT scans of dental clinic

the maxillary sinusitis mucosal thickness and the causes of OMS were recorded

as well as the anatomic relationship between the roots and the floor of maxillary sinus.       Results      Among the maxillary sinusitis patients

27.5% of OMS was detected

and the incidence was more frequent in the patients of 59 years old (P0.01). Meanwhile

periapical periodontitis was found to be the main cause. The OMS was caused by pathogenic teeth in 35% patients. The probability that pathogenic teeth whose root tips entered the sinus floor (category A) or touched the sinus floor (category B) caused maxillary sinusitis was higher than the probability that pathogenic teeth having gap or space with the sinus floor (category C) caused maxillary sinusitis (P0.01)

but there was no statistically difference between category A and B (P0.05).       Conclusion      The probable causal relationship between OMS and odontopathy can be displayed well with CBCT. The incidence of OMS in chronic maxillary sinusitis is relatively high in the elderly male patients. In the periapical disease with pathogenic teeth whose roots are close to the floor of maxillary sinus

OMS needs to be given more attention.