The trial was stopped earlier than planned because of the slow accrual rate.

Antibiotic resistance is a worldwide problem closely linked to antibiotic consumption. To limit the risk to select resistant bacteria, the rules of prescription are to use high doses and short durations of treatment. The purpose of this study was to evaluate the interest to reduce amoxicillin treatment from 7 days to 3 days, in cases of odontogenic infection requiring the extraction of the tooth associated with amoxicillin monotherapy. The 3-day treatment will be compared to the classical 7-day treatment for clinical efficacy (pain, wound healing) and impact on the susceptibility of oral streptococci to amoxicillin.

Amoxicillin treatment starts the day of the inclusion in the study (day 0). Dentists and participants were blinded to treatment assignment for the duration of the study. The infected tooth was extracted 2 days after the beginning of the antibiotic treatment, and the post-operative follow-up was done 1 week after tooth extraction (day 9). An additional follow-up was done one month later (day 30).

Clinical parameters were collected one week after tooth extraction (day 9). Pain was evaluated by its intensity during the days following surgery (using an analog visual scale varying from 0 -no pain- to 10 -very intense pain-), and by the total amount (in mg) of paracetamol ingested. The infectious state was evaluated by local wound healing, regional adenopathy and fever. The wound healing score combined local inflammation and sensitivity, and the presence or absence of a blood clot.

The streptococci resistance was assessed at the patient-level by the proportion of patient with at least one resistant streptococcus, and at the streptococcus-level by the proportion of resistant streptococcus out of the total streptococci flora. Intermediate susceptibility to amoxicillin was defined as a minimum inhibitory concentration (MIC) of 0.5-16 mg/L; resistance was defined as an MIC greater than or equal to 16 mg/L.

Inclusion Criteria:

• odontogenic infection requiring tooth extraction asociated with amoxicillin monotherapy
• good condition
• 18-60 years old
• written informed consent provided

Exclusion Criteria:

• antibiotic prophylactic treatment
• special infectious risk (immunodeficiency, diabetes..)
• pregnant or breastfeeding women
• amoxicillin contraindication
• antibiotic treatment during the lasts 45 days