The purpose of the present study was to develop and evaluate a preventive dental program at two Danish chocolate factories. The program was undertaken within the setting of an occupational health service in order to control oral occupational diseases. Eighty-nine persons (80%), 19-61 yr of age, participated in a 2-yr follow-up study. Preventive care was offered to the workers by a dental hygienist. Clinical prophylaxis was given at four visits the first year and two visits the second year. Health education was based on active involvement of the participants and safety committee or safety group members in order to stimulate self-care activities at the factories. The outcome of the program was evaluated by clinical recordings of visible plaque index (VPI), gingival bleeding (GB), calculus index (CI), and DMFS. Data on dental conditions were recorded at baseline, after 12, and after 24 months. Questionnaires were completed by the workers each time in order to obtain data on dental knowledge, attitudes, dental health behavior, social network activities, and perceptions of the process. The results showed improvement in dental health in terms of stepwise reductions in VPI, GB, CI, and DS. For example, mean GB decreased from 36% of the teeth scored at baseline to 9% at 24 months and mean DS decreased from 2.3 to 0.7. Positive developments of dental health behavior were observed. The proportion of workers reporting daily toothbrushing at work increased from 6% to 24% during the program and the proportion of workers using dental floss regularly increased from 24% to 47%. However, the changes in dental knowledge and attitudes were rather diffuse.(ABSTRACT TRUNCATED AT 250 WORDS)