Objective: To assess whether inability to afford dental care is associated with the number of teeth with untreated dental caries and whether this association is independent of socioeconomic factors and ethnicity. Basic research design: Data were from the National Health and Nutrition Examination Survey (NHANES) (2015-2018), a cross-sectional national survey of non-institutionalised Americans. Clinical setting: The survey included clinical assessment of tooth condition, data on sociodemographic factors, use of dental services, health insurance, number of teeth and affordability of dental care when needed. Participants: The analysis included 9,440 participants aged 18 years and over. Main outcome measures: The association between number of teeth with untreated caries and affordability of dental care was assessed adjusting for age, gender, ethnicity, income, education, dental visits, and health insurance. Results: The mean number of teeth with untreated caries was 0.51, and 13% reported inability to afford care. Mean numbers of teeth with untreated caries among those unable and able to afford dental care were 1.46 and 0.36, respectively. In the fully adjusted model, the rate ratio for teeth with caries among those who could not afford dental care was 2.45 (95% Confidence Intervals ‘CI’: 2.04, 2.95). Income and education inequalities were slightly attenuated after accounting for inability to afford care. Other statistically significant predictors included education, and irregular dental visits. Conclusion: Inability to afford dental care may exacerbate inequalities in dental caries. The findings highlight the need for affordable access to dental services. Keywords: Dental Caries, Affordability, Dental Care, Socioeconomic Status