Background: For over ten years, dental cellulitis management is not so longer simple: more and more patients need long-time hospitalization, several surgical interventions and intensive care follow-up. This prospective study seeks to highlight criteria that can split patients with severe odontogenic infection into two main groups: those with simple evolution after treatment of the infection and those for whom complex management is necessary to obtain healing.Methods: All patients with severe odontogenic infection (namely patients which necessitated hospital admission, intravenous antibiotherapy and general anesthesia) were prospectively recorded between January 2004 and December 2014. Statistical tests used were: chi-square test (or Fisher’s exact test when appropriate) for categorical data, and Student t-test (or Mann & Withney test when appropriate) for continuous data; statistics were computed with STATA V12 (Stata Corp, College Station, Texas, USA) and with R (R version 3.0.2; The R Foundation for Statistical Computing, Vienna, Austria; http://www.r-project.org).Results: A total of 653 patients were included in the study, 611 (93.6%) had one surgery, 42 (6.4%) had more than one surgery (range 2 – 15 surgeries) before healing. In multivariate analysis, objectives criteria which emerge are: C-reactive protein (CRP) level (CRP>200 mg/l, p=0.01, OR=4.12 IC95%=[1.33-12.72]), alcohol abuse (p=0.03, OR=2.70 IC95%=[1.09-6.7]), penicillin allergy (p=0.001, OR=5.47 IC95%=[1.99-15-09]), mandibular molar infection (p= 0.02, OR=2.74 IC95%=[1.16-6.48]). A conditional inference tree (CTREE) illustrated the association of prognostic factors and the need of multiple surgery. Conclusion: Four subgroups of patients with severe odontogenic infection have a relative risk range between 25 % and 33% to have several surgical intervention associated with complications as intensive unit care follow-up, tracheotomy or death: 1- patients with CRP>200 mg/l; 2- patients with CRP between 50 and 200 mg/l and penicillin allergy; 3- patients with CRP between 50 and 200 mg/l, without penicillin allergy but with molar mandibular infection and psychiatric disorders; 4- patients with CRP ≤ 50 mg/l or unknown CRP level and immunodepression.IRB number: CE-CIC-GREN-12-08