Objective The aim of this study was to evaluate the effectiveness of a preclinical oral prophylaxis education program by examining the effectiveness of the teaching module on changes to the students' attitudes towards their individual hygiene behaviors with interdental brushes (IDBs). Methods As being part of a new didactic program on oral interproximal prophylaxis, all preclinical third-year students (n = 96) enrolled in the 2014/15 academic year received theoretical, pre-clinical, and clinical lessons on interproximal prophylaxis. The evaluation of educational outcomes was linked to observed changes in students' hygiene behaviors using interdental brushes. Knowledge, skills, attitudes, satisfaction, competence and performance were also explored. The evaluation interviews were recorded at each recall, i.e., 1 week, 1 month, 3 months and 1 year after baseline. Results Motivation to use IDBs is clearly related to the perception of the effectiveness of the brushes and the perception of bleeding reduction. At one week, 89.6% of subjects reported using IDBs. Individual use decreased significantly from one week to one month (-26%, p = 0.006) while a non-significant upward trend occurred between one month and three months. Among students reporting usage of IDBs at 1 year (20.8%), only 2.0% used IDBs daily. Most students would recommend IDBs to other people at the beginning (69.8%). However, this share dropped to 50% at 3 months. IDB-users prescribed more than non-users.