Background and Objective: This study aimed to assess the prevalence, extent, risk indicators, and intraoral distribution of underlying dentin shadows (UDS) in the occlusal surfaces of the permanent posterior teeth. Subjects and Methods: A total of 1197 adolescents were included in the study (participation rate of 72.3%). The association between the independent variables, on the one hand, and the prevalence and extent of UDS were assessed using multilevel Poisson regression models. The prevalence ratios (PR), rate ratios (RR), and 95% confidence intervals (95% CIs) were estimated. The overall prevalence of UDS was 8.8% (95% CI = 6.0–11.5), with an overall mean of 0.13 (95% CI = 0.08–0.17) lesions per individual. Those with UDS exhibited a mean of 1.45 (95% CI = 1.28–1.62) lesions. Results: Lower family income (PR = 1.58; 95% CI = 1.03–2.41) and caries activity (PR = 1.53; 95% CI = 1.01–2.31) were significantly associated with UDS prevalence, while age ≥17 years (RR = 1.43; 95% CI = 1.03–1.99) and caries activity (RR = 1.63; 95% CI = 1.55–2.30) were significantly associated with caries extent. The most commonly affected teeth were lower first molars, followed by upper first molars and lower second molars. Conclusion: This study found a low prevalence and extent of UDS in the occlusal surface. Sociodemographic variables and caries activity were associated with the occurrence of UDS.