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Using GIS to Analyze Inequality in Access to Dental Care in the District of Columbia

Learning Objectives
1. Explain a new or unfamiliar viewpoint on a topic of ethical or professional conduct
2. Evaluate the usefulness of this information for his or her practice, teaching, or conduct
3. Decide whether and when to apply the new information to his or her practice, teaching, or conduct
1 Credit CME

Background: Access to dental care in mixed-race and predominantly African American wards in the District of Columbia (DC) was investigated in relation to community development.

Methods: This study used high-resolution geographic information system (GIS) tools to map all general dentistry and periodontal practice locations in DC wards. The spatial analysis contextualized each ward's land use and demographic data obtained from DC government reports.

Findings: The analysis revealed inter-ward inequity in dental care access, which was measured by proximity to and number of dental clinics in each DC ward. Residents in affluent wards had access to many dental practices and superior amenities. Residents in wards poorly served by public transportation and with few resources had few, if any, dental clinics.

Conclusions: Dental practices are inequitably distributed across DC wards. DC policy should prioritize community development—specifically, resource allocation and community outreach—to promote health equity and improve access to and quality of dental care among residents of color.


The 2000 Surgeon General report on oral health underscored that “there are profound and consequential disparities in oral health” that primarily affect persons who are poor and have racially and ethnically minoritized identities.1 Sources of inequity include social determinants (eg, lack of financial resources, transportation, understanding of oralhealth's roles in overall health). Persons with low incomes have compromised access to insurance coverage for dental services, and Medicaid offers limited dental coverage.1,2 Dental care access inequity differs between and within states, exacerbated by shortages of dental professionals in identified areas.3,4

Regional distributions of dental services have been evaluated using models based on a geographic information system(GIS) to determine the number of new dental practices needed to allow accessibility to a dentist within a certain number of miles.5 GIS has not, however, been used to study relationships between oral health care access and community development. Accordingly, this research contextualized each DC ward's land use and demographic data, obtained from District of Colombia (DC) government reports, with spatial analysis enabled by GIS mapping of dental practice locations.


DC covers 68.34 miles of land5 and includes numerous historically African American communities. As defined by the DC Office of Planning, a ward is a district “established for administrative or political purposes” and represented by an elected council member.7 For each DC ward, we collected and summarized dental practice, land use, income, and employment status data. General dentistry and periodontal practice locations were collected online, entered into a database, and coded by specialty, street address, and zip code. Other data were obtained from DC government and census reports. We used the Quantum Geographic Information System to overlay the DC general and periodontal dental practice locations on a map of census tracts integrating population data to create a dental practice map and then overlaid ward boundaries on the map.


Quiz Ref IDResidents of DC's Ward 4 have the most access to dental care, and residents of Ward 8 have the least. Residents of Wards 1, 5, and 7 also have compromised access to dental services. (See Figure.)Quiz Ref IDQuiz Ref ID

Figure. Ward Map of Locations of DC General Dentistry and Periodontal Practices With Census Tract Population Dataa
aCensus tract-level demographic data from the 2018 American Community Survey were joined with US Census Bureau Tiger/Line shapefiles. Dental practice locations were obtained from a web-based dental directory database.8

Ward 4 is affluent, with a 2021 median income of $94 163 compared to the DC citywide median income of $91 414.9 It has low crime rates, abundant community organizations, neighborhood amenities (eg, retail), well-integrated Metrorail service, relatively high-performing public schools with strong parental support, and substantial unmet need for new affordable housing units.10 In 2021, about 31% of Ward 4 residents identified as White, a percentage slightly below the DC citywide average of 42%.9 When the wards were overlaid on the map of dental practice locations, it is apparent that there are numerous dental practices distributed throughout the ward. Taken together, the demographic data and map of dental practice locations suggest a relation between Ward 4's community development and its residents' access to oral health services.

Ward 8 communities are inhabited by residents with lower incomes and are less publicly resourced and economically developed. Although Ward 8 has been racially integrated since 1877,11 it is now about 92% African American.12 In 2021, the median household income in Ward 8 of $39 473 was the lowest in DC and less than half DC's median income.12 An influx of new residents to Ward 8 in the 1950s created economic and social disruption that continued into the 1990s. In 2000, 1 in 6 housing units in Ward 8 were vacant and 1 in 3 residents of Ward 8 lived in poverty.11 The unemployment rate of 18% in Ward 8 is about 2.5 times higher than the average of 7.3% for the DC area.12 When Ward 8 was overlaid on the map of dental practice locations, it's clear that there is a lack of dental practices.

Data on median income and population density for all the wards are displayed in the 1.

Table. Ward Statistics

WardMedian IncomeSquare MilesPopulation
Ward 1$110 3392.591 673
Ward 2$112 2446.492 809
Ward 3$143 33910.484 979
Ward 4$94 1638.987 150
Ward 5$91 18910.290 380
Ward 6$113 9225.7103 197
Ward 7$42 2018.480 669
Ward 8$39 4738.780 517

Quiz Ref IDResidents of DC wards with high percentages of persons with minoritized racial and ethnic identities and low median incomes have more limited access to oral health services than residents of more affluent DC wards. They have less access to well-integrated public transportation and must travel farther to access dental care in DC than residents of wards that have more community development and investment. These findings align with data from similar studies of other regions of the United States. For example, a GIS study in Ohio also revealed lack of access to dental care among residents in historically rural and low-income areas.5


Quiz Ref IDInequitable distribution of dental practices across DC reveals inequity in dental care access. Some residents endure more obstacles to accessing dental services than others. Identifying neighborhoods with limited access should be a public policy priority to encourage reform and innovation (eg, student loan repayment options and other incentives for oral health clinicians to practice in culturally and economically diverse communities) and would help develop public health outreach programs that promote equitable access to quality oral health services.

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The AMA Journal of Ethics exists to help medical students, physicians and all health care professionals navigate ethical decisions in service to patients and society. The journal publishes cases and expert commentary, medical education articles, policy discussions, peer-reviewed articles for journal-based, video CME, audio CME, visuals, and more. Learn more

Article Information

AMA Journal of Ethics

AMA J Ethics. 2022;24(1):E41-47.

AMA CME Accreditation Information

Credit Designation Statement: The American Medical Association designates this journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

CME Disclosure Statement: Unless noted, all individuals in control of content reported no relevant financial relationships.

If applicable, all relevant financial relationships have been mitigated.


This research was supported by grant R25DE025778 from the National Institute of Dental and Craniofacial Research of the National Institutes of Health.

Conflict of Interest Disclosure: The author(s) had no conflicts of interest to disclose.

The viewpoints expressed in this article are those of the author(s) and do not necessarily reflect the views and policies of the AMA.

Author Information:

  • Jennita Davis is a student in the Rollins School of Public Health at Emory University in Atlanta, Georgia. She is a recent graduate of Howard University's Interdisciplinary Studies Program, with a concentration in bioethics. Her research interests include bioethics, health disparities, and reproductive rights; Meirong Liu, PhD is an associate professor at the Howard University School of Social Work in Washington, DC. She has led evaluations of several federally funded programs that established multi-institutional, comprehensive, long-term partnerships to address oral health disparities and improve oral health disparity research in underserved populations. Her research focuses on program development, program evaluation, and the policies and programs that provide access to public benefits for vulnerable populations; Dennis Kao, PhD is an associate professor at the Carleton University School of Social Work in Ottawa, Ontario, Canada. His research focuses on health equity, aging-friendly communities, geographic information systems, data visualization, and digital storytelling; Xinbin Gu, MD, PhD is a professor and the associate dean of research at the Howard University College of Dentistry in Washington, DC. She is the principal investigator of the Howard University/Johns Hopkins University Summer Research Experience Program in Oral Health Disparity for Underrepresented Racial and Ethnic Students, which provides innovative training to students from underrepresented communities to conduct health disparity research and practice; Gail Cherry-Peppers, DDS, MS is an associate professor and the director of community dentistry at the Howard University College of Dentistry in Washington, DC. Her research focuses on oral health disparities and their associations with chronic diseases.

US Department of Health and Human Services.  Oral Health in America: A Report of the Surgeon General. National Institute of Dental and Craniofacial Research, National Institutes of Health; 2000. Accessed October 5, 2021. https://www.nidcr.nih.gov/sites/default/files/2017-10/hck1ocv.%40www.surgeon.fullrpt.pdf
Patrick  DL, Lee  RS, Nucci  M, Grembowski  D, Jolles  CZ, Milgrom  P.  Reducing oral health disparities: a focus on social and cultural determinants.  BMC Oral Health. 2006;6(suppl 1):S4.Google Scholar
Rural Health Information Hub.  Health professional shortage areas: dental care, by county, 2021.  Accessed October 4, 2021. https://www.ruralhealthinfo.org/charts/9
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Horner  MW, Mascarenhas  AK.  Analyzing location-based accessibility to dental services: an Ohio case study.  J Public Health Dent. 2007;67(2):113–118.Google ScholarCrossref
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 DC Health Matters.  2021 Demographics: summary of data for ward: ward 4. Updated January 2021. https://www.dchealthmatters.org/demographicdata?id=131491
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AMA CME Accreditation Information

CME Expiration Date: 01/01/2025

Credit Designation Statement:  The American Medical Association designates this Journal-based CME activity activity for a maximum of 1.00 AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Successful completion of this CME activity, which includes participation in the evaluation component, enables the participant to earn up to: 

  • 1.00 Medical Knowledge MOC points in the American Board of Internal Medicine's (ABIM) Maintenance of Certification (MOC) program;
  • 1.00 Self-Assessment points in the American Board of Otolaryngology – Head and Neck Surgery’s (ABOHNS) Continuing Certification program;
  • 1.00 MOC points in the American Board of Pediatrics’ (ABP) Maintenance of Certification (MOC) program; and
  • 1.00 Lifelong Learning points in the American Board of Pathology’s (ABPath) Continuing Certification program;

It is the CME activity provider's responsibility to submit participant completion information to ACCME for the purpose of granting MOC credit.


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