Dental Caries Experience (DMFT) and Oral Hygiene Status Among 18-Year-Old Adolescents in Two Bulgarian Municipalities: A Cross-Sectional Study

Background: As a highly prevalent chronic non-communicable disease in children and teens, dental caries continues to be a major global public health issue. Effective prevention and planning rely heavily on the systematic monitoring of oral health at key developmental ages. Objectives: This study aimed to assess dental caries prevalence and experience, alongside oral hygiene levels, among 18-year-olds using the DMFT and OHI-S indices. Additionally, differences in caries experience and oral hygiene status according to sex and place of residence were examined. Methods: A cross-sectional study was conducted (May–June 2026) involving 480 18-year-old adolescents. A stratified quota sampling design ensured equal representation by sex (male/female) and residence (urban/rural). Following informed consent, clinical indices were recorded and statistically analyzed. Results: Participant distribution by sex and residence was balanced. For the overall cohort, the mean DMFT index was 7.48 ± 4.08 (decayed: 3.91 ± 3.59; missing: 0.13 ± 0.43; filled: 3.43 ± 3.33). Females exhibited a significantly higher number of filled teeth (p = 0.004). Urban–rural comparisons revealed significant disparities in decayed (p = 0.001) and missing teeth (p = 0.015), as well as the total DMFT index (p = 0.002). The mean OHI-S score was 1.89 ± 1.01. Sex-based analysis revealed significantly poorer oral hygiene in males across all parameters: DI-S (p = 0.034), CI-S (p = 0.004), and OHI-S (p = 0.006). No significant differences in OHI-S components were observed based on residence. Conclusions: Residence was significantly associated with caries experience, while females had significantly more filled teeth than males. Poorer oral hygiene was associated with higher DMFT scores. These findings support consideration of targeted preventive oral health strategies for population groups with poorer oral health indicators and may provide preliminary evidence relevant to regional oral health surveillance and preventive planning.