The purpose of this study was to evaluate the changes in vital signs and laboratory tests of patients with odontogenic infections who required hospitalization as well as checking their effectiveness in determining the severity of the case and possible correlations with the length of stay. Patients with odontogenic infections who required hospitalization were assessed prospectively between October 2016 and April 2018. The patients were divided into two groups considered as simple (Group 1) or complex (Group 2) cases according to the length of stay. The personal data, comorbidities, signs and symptoms, vital signs and laboratory tests were analyzed. In this study, 84 cases of maxillofacial infections were detected and 50 cases of odontogenic infections were included. There were significant increases in heart rate (p = 0.012), leukocytosis (p = 0.037), neutrophilia (p = 0.021), neutrophil/lymphocyte (N/L) ratio (p = 0.044) and C-reactive protein (CRP) levels (p = 0.004) in Group 2. Additionally, there were positive correlations between the length of stay and the following variables: heart rate (p = 0.028), leukocytosis (p = 0.045), neutrophilia (p = 0.033), N/L ratio (p = 0.041) and CRP level (p = 0.003). The N/L ratio was found to have a greater value in regression analysis. It was concluded that there were significant increases in heart rate, leukocytosis, neutrophilia, N/L ratio and CRP levels for the complex cases. There were also positive correlations between the length of stay and the following variables: heart rate, leukocytosis, neutrophilia, N/L ratio and CRP level.