Background. Dental caries is a multifactorial disease and its management requires a thorough analysis of its etiological factors. Objectives. The present study used a multivariate approach to investigate the associations of socioeconomic and health-related determinants with untreated tooth decay and level of oral hygiene in adult individuals. Material and methods. A cross-sectional study involved 597 adult patients. Health and socioeconomic status were assessed using a self-administered structured questionnaire. The presence of decayed teeth was recorded clinically using the World Health Organization diagnostic thresholds. Oral hygiene level was estimated using the plaque index. Multiple linear regression analysis was used to explore the associations of socioeconomic and health-related variables with the number of decayed teeth and level of oral hygiene. Results. Socioeconomic and health-related variables explained 34.1% of the observed variation in the number of decayed teeth (p < 0.001) and 19.2% of the observed variation in the plaque index (p < 0.001). Analysis revealed several significant associations for both decayed teeth and plaque index scores. Males had 2.3 more untreated decayed teeth than women and an increased plaque index score of 0.3 units (unique contributions of 6.6 and 4.2%, respectively). An increase in self-assessed household economic status decreased the average number of decayed teeth by 1.3 and the plaque level score by 0.13 (unique contributions of 3.13% and 1.46%, respectively). Smokers presented with 1.78 more decayed teeth than non-smokers (unique contribution of 2.1%) and an increase in the plaque index by 0.48 units (unique contribution of 8.5%). Conclusions. Untreated dental caries and dental plaque severity share the same socioeconomic and health-related determinants.