<b>Introduction:</b> Odontogenic infections are polymicrobial in origin and can be life-threatening. Antibacterial failure is an important issue in the treatment of odontogenic infections. Aim: This study aimed to determine the factors associated with antibacterial failure in patients with head and neck infections of odontogenic origin.</br></br> <b>Material and method:</b> This retrospective epidemiological study was performed using data collected from 229 patients with head and neck infections of odontogenic origin who were operated on in Shahid Rajaee hospital from March 2014 to December 2019.</br></br> <b>Results:</b> 123 (53.7%) patients were female and there were 106 (46.3%) males. The mean age SD was 33.01 13.37 years (range 7 to 80). The most common offending teeth were lower molars (81.7%) and lower premolars (5.7%). The most common site of infection was the submandibular area (36.4%) followed by the buccal (20.4%) and pterygomandibular (17.1%) regions. The most common pathogen was Streptococcus haemolyticus. The length of hospitalization was higher (4.66 days) in patients with failure of treatment compared to those without it (6.00 days) (P = 0.002). A combination of penicillin G and metronidazole was prescribed for all patients with failure of treatment compared to 57.6% in patients without failure of treatment (P = 0.002). There was no statistically significant difference between the two groups regarding age, duration of illness before hospitalization, WBC, gender, history of chemotherapy, hypertension, smoking, pregnancy, alcohol consumption, diabetes mellitus, the rate of fever, trismus, dysphagia, malaise, antibiotic before hospitalization, or surgical approach.</br></br> <b>Conclusion:</b> Possible determinants in this study were not associated with antibacterial failure. Further studies should be conducted to investigate this relationship.
Keywords: Iran; antibacterial failure; odontogenic infections.