Background: Clinical experience is important in undergraduate dental education, but (suitable) patients to learn from are often lacking. Online case-based discussions were introduced to overcome patient dependency and to synchronize theoretical with clinical education. Materials and methods: Undergraduate dental students in groups of 5-7 discussed online clinical case reports presenting either minor (2nd year) or complex periodontal pathology (3rd year). Each case consisted of a brief patient history, extra-and intraoral clinical pictures, periodontal chart, peri-apical and/ or orthopantomographic radiographs. Students had to discuss diagnosis and treatment planning. Questionnaires assessed students' and supervisors' general appreciation (score on 20), time investment and opinions about organisation, relation case/course content, future planning, learning effect and online environment (5-point Likert scale). A crossover design with three tests (pre-test, test in between and post-test) was used to investigate whether the frequency of case introduction (one case per week vs. one case element per week) had an effect on learning. Data was analysed with descriptive statistics (questionnaires) and repeated measures ANOVA (crossover design). Results: Students (n = 119) and supervisors (n = 9) highly appreciated the exercise. Students reported spending on average 74 min per week to read a case, prepare and post messages. Supervisors' total time investment was 342 min per semester to create a case, provide online feedback and to prepare a live-discussion. No significant differences in test-scores were found between the two modalities of case introduction. Conclusion: Online case-based discussions, in conjunction with a theoretical course, are valuable additions to the dental curriculum, especially to reinforce the transition from theory to clinical practice.