Introduction. Dental caries constitutes an important social issue. Contemporary dentistry attempts to solve this problem by e.g. oral health promotion. Proper prophylactic measures might lead to a decrease in the incidence of caries and periodontal diseases, as well as an increase in the overall quality of life. Aim. To evaluate the influence of hygiene and dietary habits on the oral health of secondary school students on the basis of a questionnaire‑based and clinical study. Material and methods. 131 secondary school students aged 17–19, attending classes with an extended curriculum in biology and chemistry from the PUMS patron schools, were included in the study. Anonymous questionnaires comprising questions concerning oral hygiene habits were distributed. Also, a clinical examination that included the assessment of the dentition, periodontium, oral hygiene, occlusion and temporo‑mandibular joint was performed. Results. Tooth brushing is performed twice (or more) daily by 73.0% students from Poznan and 69.1% from outside Poznan. Statistically significant differences were observed for habits such as systematic tongue brushing (respectively 34.9% and 54.4%) or mouthrinse use (44.4% and 25.0%). Snacking between meals (72.5% students) and drinking beverages with a low pH (36.6% every day or more) are widespread among young people. The number of DMFT in students from Poznan is 4.0 and for students from other cities 5.0 (greater number of fillings). 16.6% of students are free of caries. Among the respondents from Poznan there was not even one extraction due to caries. The median value of the plaque index (Silness and Löe) is a sign of good oral hygiene; 0.46 for Poznan and 0.38 for others. Conclusions. Comparing the data with that in the literature, the students exhibited similar habits and oral health. However, alarming habits were also observed; e.g. the low percentage of students who brushed their teeth correctly with the roll technique (13.5%), and who used supplementary products for oral hygiene maintenance (mouthrinses – 34.4%, dental floss – 12.2%). Further education and prophylaxis aimed at adolescents should be performed in order to increase oral health awareness.

Key words: oral hygiene, secondary school students, dietary habits, caries prevention, oral health.