The incidence of odontogenic sinusitis has been gradually increasing due to the recent increases in invasive dental procedures. This study aimed to describe the clinical features of present patients with odontogenic sinusitis compared to the past, confirm the importance of endoscopic sinus surgery (ESS), and analyze the predictive factors for ESS. This retrospective review included all patients diagnosed with odontogenic sinusitis between January 2010 and December 2011 and between January 2019 and December 2020. The patients were classified into 2 groups (past and present) depending on the time of the first visit. The clinical characteristics and treatment modalities were compared between the two groups. In addition, among patients in the present group, we analyzed variables to identify factors contributing to the risk of undergoing ESS. This study included 56 patients (23 in the past group and 33 in the present group). Compared to the past group, the present group had an older mean age (P = .001) and significantly increased iatrogenic etiologies (52.1% vs 90.9%; P = .002). The proportion of patients treated with ESS also increased in the present group compared to that in the past group (39.1% vs 66.7%; P = .041). In the present group, 11 patients (33.3%) were cured with conservative treatment, while 22 patients (66.7%) underwent additional ESS. Multivariate analysis revealed that the Lund-Mackay score was the only significant predictor of ESS (odds ratio [OR]: 14.901, P = .035). The incidence of odontogenic sinusitis with iatrogenic etiologies has increased compared to the past. In addition, two-thirds of the patients in the present study underwent ESS, a significantly higher proportion than in the past. Therefore, ESS is one of the most important treatment modalities for odontogenic sinusitis, especially iatrogenic, in recent years. A severe Lund-Mackay score was associated with a significantly increased risk of ESS.