OBJECTIVE Dental practice is based upon dentists' cognitions, knowledge being foundational. Knowledge is attained through education and perception. Although knowledge is modulated by beliefs, attitudes, preferences, and behaviors, it is essential to evidence-based practice. Cross-sectional studies uniformly demonstrate that community NSRCT is of sub-optimal quality worldwide, is lack of knowledge a problem? Our purpose was to measure dentists' knowledge of root canal treatment (NSRCT). METHODS Quantitative and qualitative data were extracted: purpose, topics assessed, authors cited knowledge sources, number of dentists studied, number of questions, authors descriptors of knowledge level, % correct answers by question, authors recommendations. METHODS OVID Medline, EMBASE, Web of Science, and hand-searching. METHODS Studies which had measured dentists' knowledge of non-surgical root canal treatment that was valuable, reliable, and had practical implications which could be implemented. A total of 51 papers from 19 countries measured the knowledge of 15,580 dentists using 445 questions on 29 root canal treatment topics. CONCLUSIONS 'Gold standards' were from literature, external bodies, or expert consensus in 47, 31, and 2 papers respectively. Levels of knowledge by percentage correct answers among studies were poor to moderate and varied considerably. The mean, for the 50 studies where overall study percentages could be calculated, was 57%, standard deviation 17%, and a range of 16% to 82%. Authors' adjectives describing knowledge levels were generally negative. Additional education was advised in 49 papers, but without evidence that education was inadequate; 6 papers recommended increased use of protocols; only 5 papers advocated research on the cause of lack of knowledge. CONCLUSIONS Dentists' root canal treatment knowledge was found to be poor to moderate, as well variable. This may constrain quality of care. However, provision of information without attention to dentists' cognitions and motivations may not be successful. Educational strategies and goals should be re-evaluated. Evidence-based practice faces many barriers.