Objective The aim of this study was to evaluate the effectiveness of two amoxicillin protocols for antibiotic prophylaxis in implant placement surgeries. Methods A clinical study was performed with 66 volunteers of both genders (mean 51,9 ± 2,5 years) that met the inclusion criteria and were randomly assigned into 2 groups: Group 1 (n=35) - oral administration of amoxicillin (2g) 1 hour before the surgical procedure and Group 2 (n=31) oral administration of amoxicillin (2g) 1 hour before the

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... gical procedure and 500mg every 8 hours during 7 days after the surgeries. The following clinical parameters were evaluated: adverse reactions, pain and implants failure. The pain was evaluated in the surgery day (before, immediately after and at night), 24h, 48h, 72h and one week after the surgery and other clinical parameters were evaluated in daily appointments until the third postoperative day, 7 days and three months after the surgeries. Data were analyzed and statistical significance was 5%. Results Adverse reactions (headache, diarrhea, stomachache and nauseas) and implant failure occurred only in G2 (4 volunteers and 3 implants, respectively). Regarding pain, higher values for G2 on "at the night (p=0.0043), 24h (p=0.0013), 48h (p=0.0187) e 72h (p=0.0445) were observed. Conclusion The present study showed that a single dose of amoxicillin was effective in antibiotic prophylaxis in implant placement surgeries, suggesting that the use of amoxicillin in the postoperative period did not bring additional benefit.