The concept of shared decision making (SDM) is an important emerging trend in clinical medicine but has received little or no attention in the dental literature. Decision aids can play a useful role in SDM by helping patients and clinicians choose among reasonable alternative treatment options. The purpose of this study was to develop and test an Endodontic Decision Board (EndoDB) for chairside use to help clarify treatment alternatives, benefits, risks, prognosis, and costs when root canal therapy or extraction of a tooth was indicated. The hypothesis was that the use of the EndoDB would lead to improved patient knowledge, greater satisfaction with the decision-making process, and no difference in anxiety when compared to the standard discussion and informed consent process (usual care). The EndoDB was tested in a randomized controlled trial in a postgraduate endodontics clinic. After treatment discussion, a brief questionnaire was completed by the patient to measure knowledge, satisfaction, and anxiety. Patients in the EndoDB group (n=32) demonstrated a small, but statistically significant, increase in knowledge (t-test; difference=+0.37; p=0.03) compared to the usual care group (n=35). There was no difference between groups in the measures of satisfaction or anxiety (Mann-Whitney U-test; p>0.05). Decision aids may emerge as a useful tool to facilitate SDM and evidence-based clinical practice.