Abstract: This review included 18 double-blind placebo-controlled trials with a total of 2456 participants. Five trials were assessed at unclear risk of bias, thirteen at high risk, and none at low risk of bias. Compared to placebo, antibiotics probably reduce the risk of infection in patients undergoing third molar extraction(s) by approximately 70% (RR 0.29 (95% CI 0.16 to 0.50) P < 0.0001, 1523 participants, moderate quality evidence) which means that 12 people (range 10-17) need to be treated with antibiotics to prevent one infection following extraction of impacted wisdom teeth. There is evidence that antibiotics may reduce the risk of dry socket by 38% (RR 0.62 (95% CI 0.41 to 0.95) P = 0.03, 1429 participants, moderate quality evidence) which means that 38 people (range 24-250) need to take antibiotics to prevent one case of dry socket following extraction of impacted wisdom teeth. There is also some evidence that patients who have prophylactic antibiotics may have less pain (MD -8.17 (95% CI -11.90 to -4.45) P < 0.0001, 372 participants, moderate quality evidence ) overall 7 days after the extraction compared to those receiving placebo, which may be a direct result of the lower risk of infection. There is no evidence of a difference between antibiotics and placebo in the outcomes of fever (RR 0.34, 95% CI 0.06 to 1.99), swelling (RR 0.92, 95% CI 0.65 to 1.30) or trismus (RR 0.84, 95% CI 0.42 to 1.71) 7 days after tooth extraction. Antibiotics are associated with an increase in generally mild and transient adverse effects compared to placebo (RR 1.98 (95% CI 1.10 to 3.59) P = 0.02) which means that for every 21 people (range 8-200) who receive antibiotics, an adverse effect is likely. Although general dentists perform dental extractions because of severe dental caries or periodontal infection, there were no trials identified which evaluated the role of antibiotic prophylaxis in this group of patients in this setting. All of the trials included in this review included healthy patients undergoing extraction of impacted third molars, often performed by oral surgeons. There is evidence that prophylactic antibiotics reduce the risk of infection, dry socket and pain following third molar extraction and result in an increase in mild and transient adverse effects. It is unclear whether the evidence in this review is generalisable to those with concomitant illnesses or immunodeficiency, or those undergoing the extraction of teeth due to severe caries or periodontitis. However, patients at a higher risk of infection are more likely to benefit from prophylactic antibiotics, because infections in this group are likely to be more frequent, associated with complications and be more difficult to treat. Due to the increasing prevalence of bacteria which are resistant to treatment by currently available antibiotics, clinicians should consider carefully whether treating 12 healthy patients with antibiotics to prevent one infection is likely to do more harm than good.

Plain-language summary: This review looks at whether antibiotics, given to dental patients as part of their treatment, prevent infection after tooth extraction. There were 18 studies considered, with a total of 2456 participants who received either antibiotics (of different kinds and dosages) or placebo, immediately before and/or just after tooth extraction. There were concerns about aspects of the design and reporting of all the studies. In all of the studies healthy people had extractions of impacted wisdom teeth done by oral surgeons. This review provides evidence that antibiotics administered just before and/or just after surgery reduce the risk of infection, pain and dry socket after wisdom teeth are removed by oral surgeons, but that using antibiotics also causes more (generally brief and minor) side effects for these patients. Additionally, there was no evidence that antibiotics prevent fever, swelling or problems with restricted mouth opening in patients who have had wisdom teeth removed. There was no evidence to judge the effects of preventative antibiotics for extractions of severely decayed teeth, teeth in diseased gums, or extractions in patients who are sick or have low immunity to infection. Undertaking research in these groups of people may not be possible or ethical. However, it is likely that in situations where patients are at a higher risk of infection that preventative antibiotics may be beneficial, because infections in this group are likely to be more frequent and more difficult to treat. Another concern, which cannot be assessed by clinical trials, is that widespread use of antibiotics by people who do not have an infection is likely to contribute to the development of bacterial resistance. The conclusion of this review is that antibiotics given to healthy people to prevent infections, may cause more harm than benefit to both the individual patients and the population as a whole.