Dietary and Hygiene-Related Knowledge Versus Reported Behaviors of Eighteen-Year-Olds: A Nationwide Cross-Sectional Study

<b>Background/Objectives</b>: The aim of the present study was to examine eighteen-year-olds' self-assessed knowledge about diet and hygiene, behaviors that they report, and education they receive during dental appointments. <b>Methods</b>: Questionnaires distributed among 1611 subjects included questions concerning sociodemographic factors, dietary and hygiene knowledge and behaviors, and dental visits. Spearman's rank correlation and a bivariate and multivariate logistic regression analysis was conducted; odds ratios (ORs) and adjusted odds ratios (AORs) were calculated (<i>p</i> ≤ 0.05). <b>Results</b>: Respondents self-assessed their oral health knowledge; 63.1% of them considered it to be limited, and 40.7% understood the cariogenic effect of frequent snacking. Dentists and a dental team (DT) were the main source of information (55.7%). Dietary advice was recommended by 10.8% of dentists and the DT, while check-up appointments were advised by 49.2%. Parents' higher education contributed to a lower intake of cariogenic food. This effect was stronger for the mother's education. Dental appointments scheduled twice a year increased the chances of consuming healthy food (A2OR = 1.21 (1.07-2.11); <i>p</i> = 0.0028). Being informed increased the chances of toothbrushing ≥ 2 times (OR: 1.21, CI 1.10-1.46), using fluoridated toothpaste (OR: 1.26 CI1.05-1.55), and the frequency of appointments (A1OR: 1.56 CI 1.21-1.87; A2OR: 1.78 CI 1.54-1.91). <b>Conclusions</b>: Knowledge and oral health related behaviors, as well as the involvement of the dental team in education, are inadequate. Education and instruction in the dental office has a favorable influence on oral-health-related behaviors. It is, therefore, necessary to undertake systemic solutions so that dental practitioners are more involved. Providing oral health knowledge should be the standard of care.