Chlorhexidine (CHX) mouthwash is a good prophylactic agent for postextraction alveolar osteitis (AO), a very common complication. Recently, a bio-adhesive gel to deliver the active substance, CHX, has been introduced. The intra-alveolar positioning of the bio-adhesive gel allows more direct and prolonged action of CHX, which could be useful in the prevention of AO following extraction of impacted third molars. Presented here is a double-blind, randomised and parallel-group study evaluating the efficacy of the bio-adhesive 0.2% CHX gel (n=53) applied once within the alveolus during third molar surgery, compared to placebo gel only (n=50), in reducing the incidence of impacted third-molar postextraction AO. A 63.33% reduction in the occurrence of AO (P=0.019) was observed in the experimental group. In the control group, the occurrence of AO was 30% compared to 11% in the experimental group. Bio-adhesive 0.2% CHX gel, applied only once within the alveolus site at the time of surgery, may reduce the incidence of AO following removal of impacted third molars.