AbstractAimEvaluate the efficacy of 0.3% chlorhexidine mouthwash (CHX) and 2‐g amoxicillin (AMX) on the prevalence and nature of transient bacteraemia after surgical removal of an impacted lower third molar.Materials and MethodsThirty patients were assigned to either the CHX, AMX, or placebo groups (CTR) in a triple‐blind, randomized, placebo‐controlled trial. Blood was cultured and identified at three time points; baseline, 30 s and 15 min following flap incision. Samples were processed for using BACTECTM FX and then Matirx‐assisted laser desorption/ionization‐time of flight mass spectrometry for positive identification.ResultsThe prevalence of transient bacteraemia was 50% in the CTR group, and 10% each in the CHX and AMX groups. At 30 s, there was no difference in the prevalence of transient bacteraemia in the CHX (10%), AMX (10%) and CTR (30%) groups (p = 0.477). However, at 15 min, there was a statistically significant difference in the prevalence of bacteraemia between the CHX (0), AMX (10%) and CTR (40%) groups (p = 0.029). The majority of cultures yielded gram‐positive cocci. The most frequently isolated organisms were viridans streptococci and Actinomyces oris.Conclusion0.3% CHX is effective in preventing postoperative bacteraemia for at least 15min and may be considered as a prophylaxis antiseptic prior to thrid molar surgery.The trial was registered and approved by Thai Clinical Trails Registry Committee (TCTR20210531006).