The present retrospective analysis sought to investigate the impact of the oral care programme (OCP) for adults provided at the Department of Conservative and Preventive Dentistry, Justus-Liebig-University of Giessen, Germany, on oral health parameters. The OCP was modular and included oral hygiene instruction/professional toothcleaning, nutrition counselling, fluoridation and re-motivation. From 1999-2014, data from 1665 patients (55.1% female, 44.9% male; median age 33 years, range 15;80) were available. Type/date of modules, % of proximal sites with plaque (PP) and with bleeding after probing (PB) and D3/4MFT/D3/4MFS were recorded. PP and PB values are given as median (min;max). Overall, 60.2% of the patients attended the OCP once, 19.1% twice, and 20.7% ≥ three times. Initially, PP/PB were 0.68(0;1)/0.08(0;1) resp. decreasing at visit two (0.62(0;1)/0.07(0;1) resp.; p≤0.001 each) with no further improvement over next visits. Patients with poor oral hygiene improved, but those with good oral hygiene worsened (p≤0.001 each). Shorter intervals between visits were more effective than longer intervals. Attendance patterns changed significantly over the years: earlier, patients attended more visits with different modules; later, patients preferred the oral hygiene module and the intervals between visits lengthened. Prevalence and incidence of caries was associated with higher PP levels. Attendance patterns changed over time and had a significant impact on the outcome of the OCP. The improvement of oral hygiene was limited and occurred within the first two visits; repeated sessions maintained this improvement. The results indicate the need for new strategies improving patients' skills for efficient hygiene techniques.