Association Between Area Deprivation and Dental Provider Density in California: A Cross-Sectional Ecological Study

Abstract Background Neighborhood socioeconomic disadvantage may contribute to inequities in access to dental care by influencing the geographic distribution of providers. The Area Deprivation Index (ADI) is a validated measure of neighborhood deprivation, but its association with dental workforce availability has not been examined statewide in California. This study evaluated the relationship between neighborhood deprivation and dental provider density across California ZIP Code Tabulation Areas (ZCTAs). Methods We conducted a cross-sectional ecological study of California ZCTAs using publicly available data from the National Plan and Provider Enumeration System (April 2026), the Neighborhood Atlas 2023 ADI, and 2024 U.S. Census population estimates. Active dental providers were linked to ZCTAs and provider density was calculated per 10,000 residents. ADI was aggregated to the ZCTA level using the median ADI national percentile. Negative binomial regression was used to assess the association between ADI and dental provider density, with population included as an offset. Secondary analyses examined California-specific ADI quartiles, dental deserts, and specialist versus general dentist availability. Results The final analytic sample included 1,426 California ZCTAs representing 39,016,384 residents and 37,945 active dental providers. Greater neighborhood deprivation was significantly associated with lower dental provider density. Each one-percentile increase in ADI corresponded to a 1.8% reduction in provider density (incidence rate ratio [RR] 0.9823, 95% confidence interval [CI] 0.9799-0.9847; p < 0.001). Compared with the least deprived quartile, the most deprived quartile had 61% fewer dental providers (RR 0.39, 95% CI 0.34-0.45; p < 0.001). Overall, 15.9% of ZCTAs contained no active dental providers, increasing from 6.8% in the least deprived quartile to 31.1% in the most deprived quartile. Specialist availability demonstrated an even steeper deprivation gradient, with specialist density declining by 86% between the least and most deprived quartiles.