In this study, we retrospectively evaluated a large patient population with oromaxillofacial infections. To our knowledge, there is no retrospective or prospective study available, which evaluates the perspective of orofacial infections in South Korea. The demographic data of our study were consistent with the other studies published in English. In this study, males predominated (55.35%); Zhang et al.  reported the proportion of males to be 59.0%. Many other authors also reported a predominance of males, as high as 66% [15, 16]. The mean age of patients in this study was 47.13 ± 19.9 years, similar to that of Zhang et al.  (47.5 years) and Allareddy et al.  (40 years). Mandibular molars were the most frequently involved teeth in odontogenic infections, with these teeth being the cause of infection in 72.4% of cases in Gholami’s study . Odontogenic infection was implicated in 63% of cases of maxillofacial region infection , lower than the 92.47% of the present study. This is because that the patients were referred after classification in an emergency department. In the Ottaviani et al.  study, which included the vestibular space, multiple-space infection was reported in 8.86%  of cases, compared with 11.71% of our study. In addition, only 2.76% received inpatient treatment, which differed from our result of 29.77%. Excluding the vestibular space, the submandibular is the most commonly infected space, a finding similar to other published studies [13, 16].
Flynn et al.  found that severity scoring for the number of infected spaces and the site of the infected space appeared to be valid measures of the severity of infection. In our study, severity of infection such as number of infected spaces [3, 11, 18] and site of infection  was associated with the requirement for hospitalization. Sharma et al.  found that the level of C-reactive protein (CRP) can be an effective marker for determining the severity of infection, a finding confirmed by other studies [20, 21].
Regression analysis showed a statistically significant association between long-term hospital admission and patients being of an older age and having diabetes. This finding was consistent with other studies [4,5,6, 12, 15, 22, 23]. Interestingly, several variables indicating the severity of infection were not associated with an increased length of hospitalization. These results do not support the findings of Flynn et al. . Among the papers related to the hospitalization period, the identified risk factors were derived to be irrelevant in this study such as medically compromising diseases (with the exception of diabetes), number of infected spaces , and site of infection . This is because older patients and patients with diabetes had lower defense against pathogenic infections, and their recovery rate was low . Host immune mechanisms are important to resolve infection . From those results, regardless of the factors associated with severity of infection, patients can be expected to heal well by removing the infection source and performing proper drainage. If the initial treatment is done properly, length of stay may not be associated with severity of infection.
In this study, a long hospital stay is defined as ≥ 12 days, which was the average length of hospitalization. Patients generally remain hospitalized until the infection resolves or is controlled, and until the patient is returned to a pre-infection state of health. In various studies, the criteria for prolonged hospitalization differ between studies. Usually, hospitalization over the average period is considered long-term admission. In the USA, the average length of stay was 3 to 8.3 days [5, 16, 17, 24]; in Iran, it was 6.8 days ; in Finland, it was 14.8 days ; and in China, it was 12 days . This indicates that the length of hospitalization is different in different regions of the world when similar adult infections are compared; however, the number of studies comparing hospitalization length among different countries is too low to make an accurate comparison. Also, in this study, we included non-odontogenic infection, which may differ in terms of treatment progress of odontogenic infection. Finally, the length of hospital stay can be affected by financial factors. There is a difference in the cost of hospitalization because the system of health insurance is different in each country . In the USA, daily mean room and bed charges ranged from $978 to $1598 ; on the other hand, in South Korea, they range from $30 to $200 per day  if the patient receives national health insurance. Due to expensive hospital costs, studies in the USA reported average hospital stay as shorter (3 to 8.3 days), compared with 12 days in this study.
The main limitation of this study was its retrospective study design. Because of the nature of retrospective studies, there is a need to rely on medical records to evaluate and measure the variables used in the study. Most studies regarding oromaxillofacial infections were conducted on a uniform group of patients, such as those with odontogenic or non-odontogenic infections. Moreover, previous studies assumed that the patient group and severity of symptoms in the environment of the emergency room are different from those of the outpatient setting. Hence, in future studies, it may be necessary to consider the differences between the emergency department patients and outpatients.