Preoperative administration of amoxicillin is not recommended in healthy patients undergoing implant surgery.

Design A multicentre, prospective, randomised, placebo-controlled, double-blinded clinical trial reported the early implant failure and postoperative infections of healthy or relatively healthy patients receiving 2 grams of amoxicillin one hour preoperatively from their scheduled dental implant placement. The registration of the study protocol in EudraCT and Clinical Trials.gov (#NCT03412305) followed the ethical principles of the Declaration of Helsinki and the CONSORT guidelines for clinical trials.Case selection Several trial drugs expired before recruiting the intended 1,000 patients calculated based on previous trials reporting 2% and 5% early implant loss, with and without antibiotic prophylaxis. Thus, the study cohort (age >18 years, not planned for immediate loading, not requiring substantial bone augmentation, with an absence of severe diseases or immunosuppression or immunodeficiency) received 757 implants in total between November 2014 and April 2018, consisting of the prophylactic antibiotic therapy group (patients n = 235) and the placebo group (patients n = 235), with a fair sex distribution and a mean age of 57.4 ± 13.9 years. A computer-generated list of random numbers assisted the randomisation (test or control group) with a block-size six. For the clinical procedures, bone augmentation was limited to autogenous bone chips and bone debris. One- and two-stage surgery protocols were used in maxillary or mandibular single or multiple dental implants. The utilised implant systems were Straumann SLA (Straumann Implants, Switzerland), Astra Tech Dental Implant Systems (Dentsply Sirona, Sweden), Nobel Biocare (Sweden) and Southern Implants (Ltd, South Africa). Chlorhexidine 0.2% was prescribed preoperatively and/or postoperatively. Implant failure was the main measured outcome, whereas postoperative infections and adverse events were the secondary outcomes postoperatively assessed at 7-14-day (first follow-up) and 3-6-month (second follow-up) intervals.Data analysis The sample size calculation (type one error: 0.05; power: 80%) estimated 500 patients in each group. Proportional differences and relative risk (RR) with a 95% confidence interval (CI) were calculated. Implant failure was the dependent variable for the multiple logistic regression (MLR) model examining the indicator variables smoking (yes or no), and age (<50 years; 50-64; and ≥65), as well as the independent variables bone augmentation (yes or no), number of implants (1, 2-3 and ≥4), and treatment group (antibiotic prophylaxis or placebo). P-values <0.05 or 95% CIs for ratios not including one were deemed statistically significant. The analyses were carried out using statistical software for data science (STATA).Results Overall, six (2.5%) and seven patients (3.0%) from the amoxicillin and placebo groups had implant failures, respectively. Thus, the intergroup difference was not significant (RR: 0.85; 95% CI: 0.29-2.48, p = 0.75). Absolute risk reduction was 0.46%, with a number needed to treat (NNT) of 219. In other words, one in every 219 patients will benefit from receiving prophylactic antibiotics. In addition, no variable was associated with implant failure. Two (0.8%) and five patients (2.1%) from the amoxicillin and placebo groups, respectively, had postoperative infections at the first follow-up interval. Thus, the intergroup difference was not significant (RR: 0.29; 95% CI: 0.08-2.01, p = 0.25). Five (2.1%) and seven patients (3.0%) from the amoxicillin and placebo groups, respectively, had postoperative infections at the second follow-up interval. Thus, the intergroup difference was not significant (RR: 0.70; 95% CI: 0.23-2.18, p = 0.54). No adverse events were reported.Conclusion Prophylactic antibiotic treatment for dental implant surgery to prevent implant loss may not be appropriate. Each dose must be prescribed based on evidence-based guidelines to avoid overuse and misuse of antibiotics promoting resistant bacteria.