Maxillary sinusitis (acute or chronic) is defined as a symptomatic inflammation of the maxillary sinus, usually caused by viral, bacterial, allergic, or fungal rhinitis [12]. However, any disease arising from dentoalveolar structures could damage the floor of the maxillary sinus leading to a sinusitis known as odontogenic maxillary sinusitis (OMS). The OMS is a well-recognized but understudied form of sinusitis that requires a unique treatment regimen that differs from non-odontogenic sinusitis [1].

The diagnosis of odontogenic maxillary sinusitis should be done systematically using dental examinations, radiographs, and other 3D radiographic modalities [6]. Rosenfeld et al. in his literature described CBCT as a gold standard for radiographic evaluation of the paranasal sinuses [13]. Bomeli and Matsumoto et al. concluded that unilateral maxillary sinusitis is the common radiologic finding of odontogenic sinusitis [14, 15].

The mainstay of treatment for odontogenic sinusitis is surgical therapy, and odontogenic sinusitis is often resistant to trials of antibiotics. Antibiotics, however, do play a role whenever combined with other appropriate treatments. Odontogenic sinusitis patients have a larger and more diverse microbiological burden than that observed in chronic rhinosinusitis alone, and antimicrobial therapy should address this difference [16]. Broad coverage of polymicrobial and anaerobic populations can often be achieved with a penicillin (amoxicillin) and a beta-lactamase inhibitor, with or without metronidazole [10]. Saibene et al. showed that 70% of odontogenic sinusitis isolates were susceptible to amoxicillin clavulanate, and 80% of the Staphylococcus spp. cultured were capable of producing beta-lactamase [17]. And for individuals with a penicillin allergy who cannot receive amoxicillin, doxycycline is the most appropriate treatment.

Within this study, all patients received antibiotic medication for 1 week. If symptoms improve after about 1 week of medication, administer medication for another week and follow up. If there is no improvement in symptoms, surgical treatment such as removing the odontogenic cause and irrigation of the maxillary sinus can be selected. After the dental cause is removed, primary closure is performed, and maxillary sinus irrigation is done as sinus irrigation can relieve postoperative reactions, reduce the probability of sinus infection, and protect the function of the maxillary sinus [9, 18].

To investigate the effect of maxillary sinus lavage, the volumes of opaque images in the sinus observed on CBCT were compared before and after sinus lavage. According to John’s report, who conducted a literature review, the average age of patients infected with odontogenic maxillary sinusitis was about 51.2 ± 3.9, and the age ranged from 43 to 58 years. The mean ages of males and females were 49.4 ± 10.8 years (range 33–67) and 50.6 ± 10.8 (range 33–67) years respectively [19]. According to our results in Table 1, out of 21 patients, 16 were male, and 5 were female. So, it can be said that there were more male patients than females. The age distribution ranged from 26 to 80 years, and the average age was 53.71 ± 15.27 years. The difference between the mean ages of males and females was not statistically significant. At a young age, many cases of oral disease can lead to an odontogenic disease, and minor surgeries such as tooth extraction or implantation are rare, so it is thought to be most prevalent in the middle age.

According to a paper published by Matthias in 2015 based on 174 cases, oroantral fistula after tooth extraction was the most common cause with 60 cases (34.5%), followed by peri-implantitis in 9 cases (5.2%). Sinus lift was the cause in four cases (2.3%), which accounted for a relatively low proportion [20]. Contrary to this, according to Kim et al., out of 27 patients, 10 patients (37%) had maxillary sinusitis due to implant, and 8 patients (29.6%) had maxillary sinusitis due to tooth extraction [8]. In Table 2, it is shown that the causes of dental maxillary sinusitis were related to implant placement; removal and peri-implantitis in 7 cases (33.3%); bone graft in 7 cases (33.3%), which accounted for the most proportion; and tooth extraction in 5 cases (23.8%).

Several causes may contribute to implant failure. In a prior investigation into the late stages of chronic sinusitis-related implant failure, it was found that long implant apex perforation into the sinus, microbe infection, and contamination of potentially toxic elements may be major factors in dental implant failure linked to maxillary sinusitis [21, 22]. According to Kim et al. case report, who performed lateral sinus irrigation on two patients with maxillary sinusitis after implant surgery, it was observed that all opaque images on cone beam CT decreased significantly 2 weeks after sinus irrigation [23]. According to Fig. 2, opaque images on radiographs improved in most cases after maxillary sinus irrigation. However, in some patients with maxillary sinusitis caused by implant placement (may due to severity of peri-implantitis or degree of osseointegration) and bone grafting, opacity increased because the bone particles were not easily washed away and remained at its position [24].

Gang et al. showed that the chronic maxillary sinusitis was healed within 8–12 weeks of Caldwell–Luc surgery followed by sinus irrigation. None of the patients complained about nasal obstruction or facial paresthesia, and no further major complications were noticed after 36 months of surgery [9]. In our study, Fig. 3 shows the change in clinical symptoms after maxillary sinus irrigation. It was found that the symptoms improved in 17 out of 21 patients, and no patient’s condition jeopardized.

Bomeli et al. in his literature found that around 79% of sinuses had opacity, and its cause was unknown dental source [14]. Likewise, Maillet et al. found that 72.5% had odontogenic cause, whereas 27.5% had unknown dental cause [25]. However, according to our study, as shown in Fig. 4, the radiopacity of maxillary sinusitis patients was highest in bone transplant patients (81.6%). The effect of maxillary sinus irrigation was the greatest in extraction patients and the least in implant patients except for others.

Therefore, we can say that sinus irrigation through lateral window approach is an effective treatment method. However, the few limitations of this study were retrospective nature, small number of patients, and long-term follow-ups. Therefore, further study should be done to generalize our results.