The objective of this study was twofold, namely to evaluate the effectiveness of a dental clinical practice guideline on the management of asymptomatic impacted lower third molars (i) on referral rates and (ii) on dentists' change in knowledge. A two-arm cluster randomized controlled trial, with pre- and post-test assessments, was conducted. A guideline was implemented by multifaceted interventions (i.e. feedback, reminders, and an interactive meeting). The effect was evaluated after 1 yr by repeating the baseline questionnaire and by monitoring the number of patients who were referred for removal of their asymptomatic impacted mandibular third molars. Instruments were questionnaires for detecting changes in knowledge, patient records, and panoramic radiographs. The knowledge of dentists regarding asymptomatic mandibular third molar management was found to increase significantly in the intervention group as compared to the control group. There was no statistically significant difference between the groups in guideline-consistent patient referral rates at the post-test assessment. It was concluded that the methodology employed for dissemination and implementation of a clinical practice guideline on asymptomatic mandibular third molar management improves dentists' knowledge on this topic and is effective in improving decision-making in simulated cases; however, no clinical effect was demonstrated.