Purpose: To compare the efficacy of three different antibiotic regimens in reducing early dental implant failure. Materials and methods: In a controlled clinical trial, 270 consecutively treated patients were allocated to three antibiotic groups, alternatively, according to order of participation in the trial: Group A (2 g amoxicillin single preoperative dose), Group B (single preoperative 2 g amoxicillin followed by 500 mg three times daily for 5 days) and Group C (postoperative amoxicillin with clavulanic acid 625 mg three times daily for 5 days). Outcomes were pain, wound infection, dehiscence, adverse events possibly related to antibiotics and early implant failure. The patients were followed postoperatively at 1 week, 1 month and at the beginning of the prosthetic stage. Chi-square test and ANOVA test were used to examine differences. Results: In total, 240 patients were adherent to the trial protocol: Group A, 73 patients (210 implants); Group B, 79 patients (266 implants); and Group C, 88 patients (290 implants). Patients experiencing early implant failure: 12 in Group A (16.4%), 11 in Group B (13.9%) and 13 in Group C (14.8%). No statistically significant differences were observed for any of the outcome measures between the three groups. Conclusions: It may not be necessary to provide postoperative antibiotics in patients undergoing dental implant placement, however, these preliminary findings need to be confirmed by large multicentre clinical trials. Keywords: antibiotic prophylaxis, controlled clinical trial, dental implant, failure