Background <p>To investigate the epidemiological prevalence and sociodemographic determinants of chronic temporomandibular disorders (TMD) in South Korea using a standardized case definition from national healthcare data, with emphasis on age, sex, socioeconomic status, and residential distribution.</p> Methods <p>Data from the Korean National Health Insurance Service (2006 to 2019) were analyzed. Patients aged ≥ 20 years with three or more TMD-related visits (K07.6) were classified as chronic TMD. Sociodemographic factors included age, sex, income quintiles, and residential region. Treatment modalities were evaluated through associated diagnostic, medication, and procedural codes.</p> Results <p>Standardized prevalence of chronic TMD increased from 6.28 per 10,000 in 2010 to 12.09 in 2016, stabilizing at 9.53 in 2019. Female predominance was observed (66%), though the female-to-male ratio decreased from 2.37 to 1.68 over the study period. The highest prevalence occurred in the 20–29 year cohort (0.21%), with higher rates among high-income groups. Additionally, 49.3% of cases were concentrated in metropolitan areas. Pharmacotherapy represented the predominant intervention (95.92%), while invasive procedures such as arthrocentesis (1.07%) and TMJ surgery (0.63%) were infrequently employed.</p> Conclusions <p>This comprehensive analysis reveals distinct sociodemographic gradients and treatment preferences, providing valuable insights for healthcare planning, and highlighting the need for further research on TMD’s relationship with socioeconomic factors.</p>