The objective of this study was to assess the knowledge about oral cancer, in particular about diagnostic items and risk factors, after educational intervention by means of a standardized survey. On the basis of the evaluation at baseline, an educational programme consisting of different approaches (for instance, oral presentations, poster, DVD and a brochure) was designed. In May 2009, the questionnaire 'Practices and opinions about oral cancer' focusing on the knowledge about diagnostic factors and risk factors for oral cancer was mailed to every dentist in Schleswig-Holstein, Germany (n = 2280). The results were based on 394 of 2280 questionnaires. After a 1-year educational intervention, the dentists' overall knowledge about diagnostic procedures and risk factors for oral cancer had improved. The low baseline results for diagnostic procedures and risk factors showed the highest improvement rate immediately after the intervention. Within the reevaluation subgroups, responders who had attended a continuing education course during the intervention period showed better results compared with the whole sample of the reevaluation. The results showed that a structured educational programme with different approaches increases dentists' knowledge about diagnostic procedures and risk factors. This intervention may not only give useful recommendations for further educational courses, but emphasizes the necessity of attending continuous further educational courses.