Purpose: Chlorhexidine is a good prophylactic agent for post-extraction dry socket alveolitis. The bio-adhesive 0.2% chlorhexidine gel could improve this action since its intra-alveolar positioning would allow a more direct action on the alveolus and more prolonged action of the medication. Materials and Method: We present a single blind, randomised study on 30 patients to evaluate the efficacy of the bio-adhesive 0.2% chlorhexidine gel, placed only once within the alveolus, on the reduction of the incidence of impacted third molar postextraction dry socket alveolitis and its post-operative effects on patients. Results. A reduction of 42.65% in the occurrence of alveolitis and a more favourable post-operative period in the experimental group was observed. In the control group, the appearance of alveolitis was 30.76% opposite to 17.64 % in the experimental group. Conclusions: The bio-adhesive 0.2% chlorhexidine gel, applied only once after the extraction of impacted third molars, seems to be an appropriate option for the reduction of alveolitis. It improves the buccal aperture and oedema in the post-operative period, although further double blind studies with larger samples are necessary.