AbstractTo evaluate the effect of repeated dental health care instructions plus a single initial prophylaxis a study was conducted in the Dutch Royal Military Academy. The experimental group consisted of second year cadets and the control group of first year students. The final examination took place 1 year after the baseline examination. After the final examination the study was repeated to see whether the results of the first experiment were reproducible. Experimental effects were measured by a questionnaire and dental indices. The results of the study showed significant and relevant improvements in dental knowledge, attitude, reported behavior, the participants' perception of the gingival status, the ability to diagnose gingivitis and the condition of the supporting tissues. The effects were reproduced in the second experiment.