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Pediatr Dent. Author manuscript; available in PMC 2016 July 01. Published in final edited form as: Pediatr Dent. 2015 ; 37(4): 371–375.
Pediatric dentist density and preventive care utilization for Medicaid children James F. Heidenreich, DMD, MPH, MSD1, Amy S. Kim, DDS2, JoAnna M. Scott, PhD3, and Donald L. Chi, DDS, PhD4 1
Dr. Heidenreich practices pediatric dentistry in Phoenix, AZ
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2
Dr. Kim is a clinical assistant professor at the University of Washington’s Center for Pediatric Dentistry
3
Dr. Scott is an acting assistant professor in the Department of Pediatric Dentistry at the University of Washington
4
Dr. Chi is an associate professor in the Department of Oral Health Sciences at the University of Washington
Abstract Purpose—This study evaluates the relationship between county-level pediatric dentist density and dental care utilization for Medicaid-enrolled children in Washington State.
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Methods—This is a cross-sectional analysis of 604,885 children ages 0-17 enrolled in the Washington State Medicaid Program for ≥11 months in 2012. The relationship between countylevel pediatric dentist density, defined as the number of pediatric dentists per 10,000 Medicaidenrolled children, and preventive dental care utilization was evaluated using linear regression models. Results—In 2012, 179 pediatric dentists practiced in 16 of the 39 counties in Washington. County-level pediatric dentist density varied from zero to 5.98 pediatric dentists per 10,000 Medicaid-enrolled children. County-level preventive dental care utilization ranged from 32 percent to 81 percent, with 62 percent of Medicaid-enrolled children in Washington utilizing preventive dental services. After adjusting for confounders, county-level density was significantly associated with county-level dental care utilization (β=1.67, 95 percent CI=0.02, 3.32, p=0.047).
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Conclusions—There is a significant relationship between pediatric dentist density and the proportion of Medicaid-enrolled children who utilize preventive dental care services. Policies aimed at improving pediatric oral health disparities should include strategies to increase the number of oral health care providers, including pediatric dentists, in geographic areas with large proportions of Medicaid-enrolled children.
All authors have made substantive contribution to this study and manuscript, and all have reviewed the final paper prior to its submission
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Keywords Preventive Dental Care Utilization; Pediatric Dentist Density; Dental Workforce; Access to Care; Medicaid
INTRODUCTION
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There are significant disparities in oral health among children in the United States. Economically disadvantaged children are a particularly vulnerable group1. Data from the National Health and Nutrition Examination Survey (NHANES) indicate higher caries rates among children and adolescents from low-income families2. Poor oral health affects school activity, home life, and general health, diminishing overall quality of life3. Untreated dental disease extending into adulthood can affect nutritional intake, economic productivity and have long-lasting psychological consequences4. These factors underscore the importance of developing population-based strategies to reduce oral health disparities affecting vulnerable populations. One way to improve the oral health of vulnerable children is to ensure adequate access to dental care services. An estimated 37 percent of Medicaid-enrolled children utilize any dental services in a year, compared to 55 percent of privately-insured children5. Dental utilization rates are even lower among certain Medicaid subgroups, including preschoolaged children6. Fifteen-percent of children enrolled in Medicaid fail to receive needed dental care because a dental provider refused to accept Medicaid5.
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There are a number of potential strategies to reduce disparities in dental care utilization. One approach is to increase the dental workforce, particularly in areas of high need. Traditionally, dentist shortage areas have been defined as the proportion of dentists to total population in a geographic area7. This measure, however, may not be relevant in estimating dental need among pediatric populations. The availability of pediatric dentists within a geographic area may be a better measure of resources available to families with children. Pediatric dentists receive at least two additional years of clinical training beyond dental school that prepares them to address the unique dental needs of children. Pediatric dentists are most likely to practice in areas with higher numbers of general dentists and where higher percentages of adults with a college degree live8. Unfavorable pediatric dentist-to-child ratios are found mostly in rural states9. In other words, rural areas have disproportionately fewer pediatric dentists to serve children.
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No studies to date have looked specifically at pediatric dentist density and utilization of dental services among Medicaid enrollees. Early work by Groenewegen and Postma found demand for dental services among publicly-insured adult patients was positively associated with the dentist density of the area in which they lived10. A study of women of childbearing age in Ohio found no significant relationship between dentist density and dental service utilization11. For Medicaid-enrolled children in Alabama, availability of a dentist in the county of residence who accepted Medicaid patients was significantly associated with receiving dental sealants12.
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This study evaluated the relationship between the pediatric dentist-to-child ratio and preventive dental care utilization for Medicaid-enrolled children through a cross-sectional, secondary data analysis of Medicaid claims data. Our hypothesis was that county-level pediatric dentist density was positively associated with county-level dental care utilization for Medicaid-enrolled children. This study is important because it will shed light on the extent to which the availability of pediatric dentists influences dental care utilization for underserved children, and is expected to help policymakers improve programs aimed at reducing disparities in dental care utilization for Medicaid-enrolled children.
METHODS Data Sources and Human Subjects Protection
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A dataset including children ages zero to17 years enrolled in the Medicaid program and associated dental claims for the year 2012 was obtained from the Washington State Health Care Authority. The data included each child’s age, race, gender, and county of residence. County-level variables were obtained from the 2012-2013 Area Health Resource File (AHRF), distributed by the U.S. Department of Health and Human Services Health Resource and Services Administration, and from the U.S. Census Bureau. Historical information on pediatric dentists practicing in Washington State from 2012 was obtained from the Washington State Academy of Pediatric Dentistry (WSAPD). The Washington State Institutional Review Board (IRB) reviewed and approved this study protocol prior to start of the study (FWA00000326). Participants
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The study population included all children ages zero to17 years enrolled in Washington Medicaid for equal to or greater than 11 months in 2012. Study variables
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Independent variable—The main predictor was pediatric dentist density, defined as the number of pediatric dentists per 10,000 Medicaid-enrolled children in a county. Data provided from the WSAPD were used to estimate the total number of active pediatric dentists practicing in each county. These dentists were verified by cross-checking the American Academy of Pediatric Dentistry (AAPD) national membership directory, dental practice websites, the Washington State Department of Health provider registry and National Provider Identification (NPI) registry. Pediatric dentistry residents, retired dentists, dentists living outside the state of Washington, and providers who were not pediatric dentists were excluded. The number of Medicaid-enrolled children was estimated from the Washington State Health Care Authority enrollment records from 2012. Outcome—The outcome of interest was the proportion of Medicaid-enrolled children utilizing any preventive dental care at the county level. We defined preventive care using Current Dental Terminology (CDT) codes, as reported in each child’s claims file. These CDT codes included D0120 (periodic oral evaluation), D0150 (comprehensive oral evaluation), D1110 (adult prophylaxis), D1120 (child prophylaxis), D1206 (topical fluoride
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varnish), D1208 (topical application of fluoride), and D1351 (sealant).13 Preventive dental services provided by physicians were not included in this study.
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Potential confounders—Six county-level variables were conceptualized as potential confounders of the relationship between pediatric dentist density and preventive dental care utilization. Four variables were derived from the AHRF: the total dentist-to-child ratio12 (total number of dentists in a county per 10,000 Medicaid-enrolled children), rurality9,14,15 (a nine-category variable defined by the U.S. Department of Agriculture Rural-Urban Continuum Code), number of community health centers16, and county Health Professional Shortage Area (HPSA) status (non-HPSA/part HPSA/full HPSA)17. There were two exploratory confounders. The first was the age of each county’s Access to Baby and Child Dentistry (ABCD) program18 (a special Medicaid access program aimed at improving the oral health of Medicaid-enrolled children under age six years). This was measured in years and calculated from the month and year in which each program was initiated. The second was regionality, defined as whether the county was east or west of the Cascades mountain range, which is a physical barrier in the state believed to affect population and health provider distribution as well as access to health care services.
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Data Analysis—Descriptive statistics were generated for all variables of interest, including child’s age, race, and gender. The county was the unit of analysis for all regression models (N=39). Unadjusted linear regression was used to evaluate for confounding and to assess the associations between each of the hypothesized confounders described previously and (1) the primary predictor variable (pediatric dentist density) and (2) the outcome variable (preventive dental care utilization). All statistically significant confounders (α=0.05) were tested for multicollinearity by measuring variance inflation factor values and were included in the final regression models if there was no evidence of multicollinearity. Unadjusted and adjusted linear regression models were constructed to evaluate the association between the primary predictor variable (pediatric dentist density) and the outcome variable (preventive dental care utilization). All data were analyzed using Stata 13 for Windows (StataCorp LP, College Station, Texas).
RESULTS Study Population
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A total of 794,117 children ages zero to 17 years were enrolled in the Washington State Medicaid program in 2012. We focused on the 604,885 children enrolled in Medicaid for equal to or greater than 11 months in 2012. The average age of children in the study population was 8.9 years (standard deviation=4.8 years). Most of the study population was White (42 percent), with the next largest component consisting of “Other Race” (26 percent). Nearly half (49 percent) of the Medicaid-enrolled children in Washington State lived in King, Pierce, Snohomish or Yakima Counties. Approximately 66 percent of the population lived in western Washington and 34 percent were in eastern Washington.
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Dental care utilization
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Mean utilization of preventive dental care services for all Medicaid-enrolled children in the state was 62 percent. County-level utilization ranged from 32 percent (Clallam) to 81 percent (Chelan). Preventive dental care utilization was notably lower among coastal counties of western Washington. All four counties bordering the Pacific coast – Clallam, Jefferson, Pacific and Grays Harbor – were among the five counties with the lowest rates of preventive dental care utilization. Preventive dental services utilization among Medicaid-enrolled children in Washington’s 21 eastern counties was 71 percent, compared to 58 percent in among those living in western Washington counties. The top 12 counties with the highest percent of children who utilized preventive dental services were all in eastern Washington (Figure 1a).
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Pediatric dentist density
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Analysis of confounders
One hundred seventy-nine pediatric dentists were identified, practicing in 16 of the 39 counties during 2012. Twenty-three counties (59 percent) had no pediatric dentists. Mean pediatric dentist density for the state was 2.96 pediatric dentists per 10,000 Medicaidenrolled children. For counties with at least one pediatric dentist, densities ranged from 1.18 to 5.98 pediatric dentists per 10,000 Medicaid-enrolled children (Figure 1b). The county with the most number of pediatric dentists was King County, with 74 pediatric dentists, or 41 percent of the state’s practicing pediatric dentists practiced, serving 21 percent of the state’s Medicaid-enrolled child population. There were 86,680 or 14 percent of Medicaid-enrolled children living in counties with no pediatric dentist.
Tests of association between pediatric dentist density, preventive dental services utilization and each of the potential confounders revealed that both ABCD program age and regionality were statistical cofounders (Table 1). There was no evidence of multicollinearity between these two confounders and both were included in the final regression models. Regression analyses
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All 39 counties in Washington State were included in the final regression analysis. An unadjusted linear regression model was performed to test the relationship between countylevel pediatric dentist density and preventive dental care utilization by Medicaid-enrolled children. This model revealed that as the ratio of pediatric dentist per 10,000 children in a county increased by one, on average, the proportion of Medicaid-enrolled children who utilized preventive dental care increased by 0.79 percent. This was not a statistically significant increase (p=0.449). Multiple variable linear regression was performed to test the association between pediatric dentist density and preventive dental care utilization by Medicaid-enrolled children in a county, after adjusting for confounders (regionality and ABCD program age). After adjusting for those confounders, as the ratio of pediatric dentist per 10,000 children in a county increased by one, on average, the proportion of Medicaidenrolled children who utilized preventive dental care increased by 1.67 percent (p=0.047) (Table 2).
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DISCUSSION In this study, we examined the relationship between pediatric dentist density and preventive dental care utilization for Medicaid-enrolled children. Consistent with our hypothesis, the final regression model indicated pediatric dentist density is significantly and positively associated with preventive dental care use for Medicaid-enrolled children. Our findings are consistent with those of Groenewegen and Postma, who described a significant increase in use of dental services among publicly-insured patients corresponding to an increase in dentist density10. Their study was survey-based and evaluated dentist density and its effects on adult utilization of any dental service. The advantage of the present study compared to Groenewegen and Postma is that we analyzed administrative claims data, thus eliminating potential recall bias and sampling error.
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The two geographic regions of Washington State appear to influence both the density of pediatric dentist density and preventive dental care utilization for Medicaid-enrolled children. Regionality therefore was found to have a confounding effect in observing the relationship between these two variables (Figure 2). As expected, the more rural eastern part of Washington had overall lower pediatric dentist density. However, preventive dental care utilization in eastern Washington counties was higher compared to counties in western Washington. This unexpected result might be explained by the role extended family and community networks play in rural counties in helping families schedule dental appointments and find transportation to the dentist office. Families may be able to more easily find dentists who accept Medicaid because rural dentists have a more visible role in the community. Additionally, the importance of preventive dental care for children may be conveyed through social networks such as farm worker communities. Given the association between regionality and preventive dental service utilization we observed, future studies should identify regional characteristics such as the role of family and unique social networks that influence dental care utilization for socioeconomically vulnerable children in rural areas. We also found ABCD program age was significantly associated with pediatric dentist density and preventive dental utilization at the county level. ABCD was first rolled out in Spokane County in 1995 and was finished rolling out in 2013. Preliminary analyses indicate ABCD has been an effective strategy to improve access to dental care for younger children in Medicaid18. It is possible there are spillover effects to older children in Medicaid. Future research should examine the relationship between ABCD program age and dental utilization rates for Medicaid-enrolled children under age six years to help tailor interventions for vulnerable subgroups that could be layered onto the existing ABCD Program.
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These preliminary findings suggest that increasing the number of pediatric dentists in areas with high populations of Medicaid children may result in improvements in access to dental care services. However, this may not be a feasible workforce policy strategy given the cost of training pediatric dentists, who may not end up practicing in areas of high need. Other proposed solutions to improve access to care for vulnerable populations have included foreign trained dentists19,20, requiring a one-year residency after dental school21, or to introduce mid-level dental providers to target oral health disparities22. Such programs need
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to focus on providing additional training on how to treat children and deploying these providers to areas of need, including areas with no pediatric dentists. The current standard for measuring dental need is based on a dentist to population ratio. This measure is used to direct federal resources aimed at influencing the distribution of dentists to areas of higher need. The findings of the present study underscore the importance of developing area-level need measures that account for the specific dental needs of vulnerable children. Taking into account the pediatric dentist-to-child ratio in defining and allocating resources to areas of need could improve child dental care utilization rates.
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There are a number of study limitations. First, our model assumes patients do not travel across county lines for dental care. The county-level density measure may underestimate geographic access to pediatric dental care when the population lives near pediatric dentists in neighboring counties. Similarly, it is possible children could have lived in multiple counties in a given year. Additional geospatial analyses, which take into account distance to dentists, travel patterns, and changes in child residence, could provide additional insight on the role of dentist density and dental care use for Medicaid-enrolled children. Second, our models only consider a dentist’s primary place of practice, as reported by the WSAPD and verified through practice websites, and the Washington State Department Public Health and NPI registries. These data sources did not provide information on how dentists might split practice time between multiple practice locations. We were also unable to account for the number of years each dentist worked in a particular county. Measuring full-time equivalents rather than number of dentists would provide a more accurate estimate of the workforce availability. In future studies, surveying or interviewing pediatric dentists to better describe workplace characteristics could address this limitation. Third, our findings are generalizable only to children in Washington Medicaid. Care should be taken before applying our findings to other states because each state may have unique patterns of dental care utilization based on state Medicaid policies, population characteristics, and regional differences. This study does however serve as a model of the process by which similar analyses could be conducted in other states to determine the effects of pediatric dentist density on dental care use for children in Medicaid. Furthermore, the Patient Protection and Affordable Care Act will enroll thousands of new adults into Medicaid, which has unknown implications for dental utilization for children23. State and federal health policy reforms underscore the importance of additional research on ways to formulate workforce policies that will address disparities in dental use among publicly-insured populations. Finally, addressing disparities in preventive dental care utilization is only part of a comprehensive solution that includes improving oral health behaviors such as tooth brushing with fluoride toothpaste and reducing carbohydrate intake. Future studies should examine ways that Medicaid access interventions can address such health behaviors so that these interventions comprehensively improve oral health outcomes for vulnerable children.
CONCLUSION Based upon this study’s results, the following conclusions can be drawn:
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1.
After adjusting for confounders, there is a significant positive relationship between the number of pediatric dentists per 10,000 Medicaid-enrolled children and the proportion of Medicaid-enrolled children who utilized preventive dental care in a given year.
2.
Each additional pediatric dentist per 10,000 Medicaid-enrolled children in a county is associated with a 1.67 percent increase in utilization of preventive dental services for Medicaid-enrolled children.
3.
Policies aimed at improving pediatric oral health disparities should include strategies to increase the number of pediatric dentists who practice in counties with large numbers of Medicaid-enrolled children and provide additional training to non-specialists who treat children in these areas.
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ACKNOWLEDGEMENTS Thank you to the Washington State Health Care Authority for providing the Medicaid datasets, the Washington State Dental Service Foundation for data on the ABCD Program, and Ms. Stephanie Cook from the WSAPD for assistance with AAPD membership data. This study was funded by the National Institute of Dental and Craniofacial Research Grant No. K08DE020856 (D. Chi).
REFERENCES
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1. U.S. Department of Health and Human Services. Oral Health in America: A Report of the Surgeon General. Department of Health and Human Services, National Institute of Dental and Craniofacial Research, National Institutes of Health; Rockville, MD: 2000. 2. Macek MD, Heller KE, Selwitz RH, Manz MC. Is 75 percent of dental caries really found in 25 percent of the population? J Public Health Dent. 2004; 64:20–5. [PubMed: 15078057] 3. Filstrup SL, Briskie D, da Fonseca M, Lawrence L, Wandera A, Inglehart MR. Early childhood caries and quality of life: child and parent perspectives. Pediatr Dent n.d. 25:431–40. 4. Hollister MC, Weintraub JA. The association of oral status with systemic health, quality of life, and economic productivity. J Dent Educ. 1993; 57:901–12. [PubMed: 8263237] 5. United States. Government Accountability Office. Extent of Dental Disease in Children Has Not Decreased , and Millions Are Estimated to Have Untreated Tooth Decay. Government Accounting Office; Washington, DC: 2008. 6. Martin AB, Hardin JW, Veschusio C, Kirby HA. Differences in dental service utilization by rural children with and without participation in head start. Pediatr Dent. 2012; 34:107–11. [PubMed: 23211894] 7. Wang F, Luo W. Assessing spatial and nonspatial factors for healthcare access: towards an integrated approach to defining health professional shortage areas. Health Place. 2005; 11:131–46. [PubMed: 15629681] 8. Solomon E. Analysis of the Demographic Characteristics of Pediatric Dental Practice Sites. Pediatr Dent. 2007; 29:214–9. [PubMed: 17688018] 9. Nainar SMH, Feigal RJ. Geographic distribution of pediatric dentists in private practice in the United States. Pediatr Dent. 2004; 26:526–9. [PubMed: 15646916] 10. Groenewegen PP, Postma JH. The supply and utilization of dental services. Soc Sci Med. 1984; 19:451–9. [PubMed: 6484630] 11. Kaylor MB, Polivka BJ, Chaudry R, Salsberry P, Wee AG. Dental services utilization by women of childbearing age by socioeconomic status. J Community Health. 2010; 35:190–7. [PubMed: 20013059] 12. Dasanayake AP, Li Y, Philip S, Kirk K, Bronstein J, Childers NK. Utilization of dental sealants by Alabama Medicaid children: barriers in meeting the year 2010 objectives. Pediatr Dent n.d. 23:401–6.
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13. Chi D, Milgrom P. Preventive dental service utilization for Medicaid-enrolled children in New Hampshire: a comparison of care provided by pediatric dentists and general dentists. J Health Care Poor Underserved. 2009; 20:458–72. [PubMed: 19395842] 14. Wall TP, Brown LJ. The urban and rural distribution of dentists, 2000. J Am Dent Assoc. 2007; 138:1003–11. quiz 1023. [PubMed: 17606500] 15. Martin AB, Vyavaharkar M, Veschusio C, Kirby H. Rural-urban differences in dental service utilization among an early childhood population enrolled in South Carolina Medicaid. Matern Child Health J. 2012; 16:203–11. [PubMed: 21153760] 16. Rosenblatt RA, Andrilla CHA, Curtin T, Hart LG. Shortages of medical personnel at community health centers: implications for planned expansion. J Am Med Assoc. 2006; 295:1042–9. 17. Chi DL, Leroux B. County-level determinants of dental utilization for Medicaid-enrolled children with chronic conditions: How does place affect use? Health Place. 2012; 18:1422–9. [PubMed: 22981229] 18. Kobayashi M, Chi D, Coldwell SE, Domoto P, Milgrom P. The effectiveness and estimated costs of the access to baby and child dentistry program in Washington State. J Am Dent Assoc. 2005; 136:1257–63. [PubMed: 16196230] 19. Bazargan N, Chi DL, Milgrom P. Exploring the potential for foreign-trained dentists to address workforce shortages and improve access to dental care for vulnerable populations in the United States: a case study from Washington State. BMC Health Serv Res. 2010; 10:336. [PubMed: 21143987] 20. Mick SS, Lee SY, Wodchis WP. Variations in geographical distribution of foreign and domestically trained physicians in the United States: “safety nets” or “surplus exacerbation”? Soc Sci Med. 2000; 50:185–202. [PubMed: 10619689] 21. Lamster IB, Eaves K. A model for dental practice in the 21st century. Am J Public Health. 2011; 101:1825–30. [PubMed: 21852631] 22. Friedman JW, Mathu-Muju KR. Dental therapists: improving access to oral health care for underserved children. Am J Public Health. 2014; 104:1005–9. [PubMed: 24825199] 23. Dubay L, Kenney G. Expanding Public Health Insurance to Parents: Effects on Children’s Coverage under Medicaid. Health Serv Res. 2003; 38:1283–302. [PubMed: 14596391]
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Author Manuscript Figure 1.
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Preventive Dental Care Utilization for Medicaid- enrolled Children in Washington State by County, 2012. (B) Pediatric Dentist Density in Washington State by county, 2012
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Dental care utilization and pediatric dentist density, comparing eastern and western Washington State counties, 2012
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Table 1
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Unadjusted associations between proposed confounders with pediatric dentist density and preventive dental services utilization among Medicaid-enrolled children in Washington State in 2012 (n = 39) using linear regression. Pediatric Dentist Density
Preventive Dental Services
Variable:
Slope
P-value
Slope
P-value
General dentist-to-child ratio
0.08
0.014*
−0.09
0.613
Number of community health centers
0.19
0.002*
0.39
0.290
Dental Health Professional Shortage Area designation
0.075
No part of county a shortage area
0.117
(reference)
(reference)
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Whole county a shortage area
−3.15
0.113
−3.18
0.766
Part of county a shortage area
−2.50
0.196
4.93
0.632
< 0.001*
Rural-Urban Continuum Codes 1 - 3 (metropolitan) (reference) 4 – 6 (nonmetropolitan) 7 – 9 (rural) Access to Baby and Child Dentistry Program age
0.201
(reference)
(reference)
−2.36
< 0.001*
−5.07
0.168
−2.72
< 0.001*
−7.38
0.115
0.19
0.005*
1.02
0.009* 0.001*
Regionality western Washington
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eastern Washington
(reference) −1.60
0.006*
(reference) 10.30
0.001*
*
p
Pediatr Dent. Author manuscript; available in PMC 2016 July 01. Published in final edited form as: Pediatr Dent. 2015 ; 37(4): 371–375.
Pediatric dentist density and preventive care utilization for Medicaid children James F. Heidenreich, DMD, MPH, MSD1, Amy S. Kim, DDS2, JoAnna M. Scott, PhD3, and Donald L. Chi, DDS, PhD4 1
Dr. Heidenreich practices pediatric dentistry in Phoenix, AZ
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2
Dr. Kim is a clinical assistant professor at the University of Washington’s Center for Pediatric Dentistry
3
Dr. Scott is an acting assistant professor in the Department of Pediatric Dentistry at the University of Washington
4
Dr. Chi is an associate professor in the Department of Oral Health Sciences at the University of Washington
Abstract Purpose—This study evaluates the relationship between county-level pediatric dentist density and dental care utilization for Medicaid-enrolled children in Washington State.
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Methods—This is a cross-sectional analysis of 604,885 children ages 0-17 enrolled in the Washington State Medicaid Program for ≥11 months in 2012. The relationship between countylevel pediatric dentist density, defined as the number of pediatric dentists per 10,000 Medicaidenrolled children, and preventive dental care utilization was evaluated using linear regression models. Results—In 2012, 179 pediatric dentists practiced in 16 of the 39 counties in Washington. County-level pediatric dentist density varied from zero to 5.98 pediatric dentists per 10,000 Medicaid-enrolled children. County-level preventive dental care utilization ranged from 32 percent to 81 percent, with 62 percent of Medicaid-enrolled children in Washington utilizing preventive dental services. After adjusting for confounders, county-level density was significantly associated with county-level dental care utilization (β=1.67, 95 percent CI=0.02, 3.32, p=0.047).
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Conclusions—There is a significant relationship between pediatric dentist density and the proportion of Medicaid-enrolled children who utilize preventive dental care services. Policies aimed at improving pediatric oral health disparities should include strategies to increase the number of oral health care providers, including pediatric dentists, in geographic areas with large proportions of Medicaid-enrolled children.
All authors have made substantive contribution to this study and manuscript, and all have reviewed the final paper prior to its submission
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Keywords Preventive Dental Care Utilization; Pediatric Dentist Density; Dental Workforce; Access to Care; Medicaid
INTRODUCTION
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There are significant disparities in oral health among children in the United States. Economically disadvantaged children are a particularly vulnerable group1. Data from the National Health and Nutrition Examination Survey (NHANES) indicate higher caries rates among children and adolescents from low-income families2. Poor oral health affects school activity, home life, and general health, diminishing overall quality of life3. Untreated dental disease extending into adulthood can affect nutritional intake, economic productivity and have long-lasting psychological consequences4. These factors underscore the importance of developing population-based strategies to reduce oral health disparities affecting vulnerable populations. One way to improve the oral health of vulnerable children is to ensure adequate access to dental care services. An estimated 37 percent of Medicaid-enrolled children utilize any dental services in a year, compared to 55 percent of privately-insured children5. Dental utilization rates are even lower among certain Medicaid subgroups, including preschoolaged children6. Fifteen-percent of children enrolled in Medicaid fail to receive needed dental care because a dental provider refused to accept Medicaid5.
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There are a number of potential strategies to reduce disparities in dental care utilization. One approach is to increase the dental workforce, particularly in areas of high need. Traditionally, dentist shortage areas have been defined as the proportion of dentists to total population in a geographic area7. This measure, however, may not be relevant in estimating dental need among pediatric populations. The availability of pediatric dentists within a geographic area may be a better measure of resources available to families with children. Pediatric dentists receive at least two additional years of clinical training beyond dental school that prepares them to address the unique dental needs of children. Pediatric dentists are most likely to practice in areas with higher numbers of general dentists and where higher percentages of adults with a college degree live8. Unfavorable pediatric dentist-to-child ratios are found mostly in rural states9. In other words, rural areas have disproportionately fewer pediatric dentists to serve children.
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No studies to date have looked specifically at pediatric dentist density and utilization of dental services among Medicaid enrollees. Early work by Groenewegen and Postma found demand for dental services among publicly-insured adult patients was positively associated with the dentist density of the area in which they lived10. A study of women of childbearing age in Ohio found no significant relationship between dentist density and dental service utilization11. For Medicaid-enrolled children in Alabama, availability of a dentist in the county of residence who accepted Medicaid patients was significantly associated with receiving dental sealants12.
Pediatr Dent. Author manuscript; available in PMC 2016 July 01.
Heidenreich et al.
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This study evaluated the relationship between the pediatric dentist-to-child ratio and preventive dental care utilization for Medicaid-enrolled children through a cross-sectional, secondary data analysis of Medicaid claims data. Our hypothesis was that county-level pediatric dentist density was positively associated with county-level dental care utilization for Medicaid-enrolled children. This study is important because it will shed light on the extent to which the availability of pediatric dentists influences dental care utilization for underserved children, and is expected to help policymakers improve programs aimed at reducing disparities in dental care utilization for Medicaid-enrolled children.
METHODS Data Sources and Human Subjects Protection
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A dataset including children ages zero to17 years enrolled in the Medicaid program and associated dental claims for the year 2012 was obtained from the Washington State Health Care Authority. The data included each child’s age, race, gender, and county of residence. County-level variables were obtained from the 2012-2013 Area Health Resource File (AHRF), distributed by the U.S. Department of Health and Human Services Health Resource and Services Administration, and from the U.S. Census Bureau. Historical information on pediatric dentists practicing in Washington State from 2012 was obtained from the Washington State Academy of Pediatric Dentistry (WSAPD). The Washington State Institutional Review Board (IRB) reviewed and approved this study protocol prior to start of the study (FWA00000326). Participants
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The study population included all children ages zero to17 years enrolled in Washington Medicaid for equal to or greater than 11 months in 2012. Study variables
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Independent variable—The main predictor was pediatric dentist density, defined as the number of pediatric dentists per 10,000 Medicaid-enrolled children in a county. Data provided from the WSAPD were used to estimate the total number of active pediatric dentists practicing in each county. These dentists were verified by cross-checking the American Academy of Pediatric Dentistry (AAPD) national membership directory, dental practice websites, the Washington State Department of Health provider registry and National Provider Identification (NPI) registry. Pediatric dentistry residents, retired dentists, dentists living outside the state of Washington, and providers who were not pediatric dentists were excluded. The number of Medicaid-enrolled children was estimated from the Washington State Health Care Authority enrollment records from 2012. Outcome—The outcome of interest was the proportion of Medicaid-enrolled children utilizing any preventive dental care at the county level. We defined preventive care using Current Dental Terminology (CDT) codes, as reported in each child’s claims file. These CDT codes included D0120 (periodic oral evaluation), D0150 (comprehensive oral evaluation), D1110 (adult prophylaxis), D1120 (child prophylaxis), D1206 (topical fluoride
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varnish), D1208 (topical application of fluoride), and D1351 (sealant).13 Preventive dental services provided by physicians were not included in this study.
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Potential confounders—Six county-level variables were conceptualized as potential confounders of the relationship between pediatric dentist density and preventive dental care utilization. Four variables were derived from the AHRF: the total dentist-to-child ratio12 (total number of dentists in a county per 10,000 Medicaid-enrolled children), rurality9,14,15 (a nine-category variable defined by the U.S. Department of Agriculture Rural-Urban Continuum Code), number of community health centers16, and county Health Professional Shortage Area (HPSA) status (non-HPSA/part HPSA/full HPSA)17. There were two exploratory confounders. The first was the age of each county’s Access to Baby and Child Dentistry (ABCD) program18 (a special Medicaid access program aimed at improving the oral health of Medicaid-enrolled children under age six years). This was measured in years and calculated from the month and year in which each program was initiated. The second was regionality, defined as whether the county was east or west of the Cascades mountain range, which is a physical barrier in the state believed to affect population and health provider distribution as well as access to health care services.
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Data Analysis—Descriptive statistics were generated for all variables of interest, including child’s age, race, and gender. The county was the unit of analysis for all regression models (N=39). Unadjusted linear regression was used to evaluate for confounding and to assess the associations between each of the hypothesized confounders described previously and (1) the primary predictor variable (pediatric dentist density) and (2) the outcome variable (preventive dental care utilization). All statistically significant confounders (α=0.05) were tested for multicollinearity by measuring variance inflation factor values and were included in the final regression models if there was no evidence of multicollinearity. Unadjusted and adjusted linear regression models were constructed to evaluate the association between the primary predictor variable (pediatric dentist density) and the outcome variable (preventive dental care utilization). All data were analyzed using Stata 13 for Windows (StataCorp LP, College Station, Texas).
RESULTS Study Population
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A total of 794,117 children ages zero to 17 years were enrolled in the Washington State Medicaid program in 2012. We focused on the 604,885 children enrolled in Medicaid for equal to or greater than 11 months in 2012. The average age of children in the study population was 8.9 years (standard deviation=4.8 years). Most of the study population was White (42 percent), with the next largest component consisting of “Other Race” (26 percent). Nearly half (49 percent) of the Medicaid-enrolled children in Washington State lived in King, Pierce, Snohomish or Yakima Counties. Approximately 66 percent of the population lived in western Washington and 34 percent were in eastern Washington.
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Dental care utilization
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Mean utilization of preventive dental care services for all Medicaid-enrolled children in the state was 62 percent. County-level utilization ranged from 32 percent (Clallam) to 81 percent (Chelan). Preventive dental care utilization was notably lower among coastal counties of western Washington. All four counties bordering the Pacific coast – Clallam, Jefferson, Pacific and Grays Harbor – were among the five counties with the lowest rates of preventive dental care utilization. Preventive dental services utilization among Medicaid-enrolled children in Washington’s 21 eastern counties was 71 percent, compared to 58 percent in among those living in western Washington counties. The top 12 counties with the highest percent of children who utilized preventive dental services were all in eastern Washington (Figure 1a).
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Pediatric dentist density
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Analysis of confounders
One hundred seventy-nine pediatric dentists were identified, practicing in 16 of the 39 counties during 2012. Twenty-three counties (59 percent) had no pediatric dentists. Mean pediatric dentist density for the state was 2.96 pediatric dentists per 10,000 Medicaidenrolled children. For counties with at least one pediatric dentist, densities ranged from 1.18 to 5.98 pediatric dentists per 10,000 Medicaid-enrolled children (Figure 1b). The county with the most number of pediatric dentists was King County, with 74 pediatric dentists, or 41 percent of the state’s practicing pediatric dentists practiced, serving 21 percent of the state’s Medicaid-enrolled child population. There were 86,680 or 14 percent of Medicaid-enrolled children living in counties with no pediatric dentist.
Tests of association between pediatric dentist density, preventive dental services utilization and each of the potential confounders revealed that both ABCD program age and regionality were statistical cofounders (Table 1). There was no evidence of multicollinearity between these two confounders and both were included in the final regression models. Regression analyses
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All 39 counties in Washington State were included in the final regression analysis. An unadjusted linear regression model was performed to test the relationship between countylevel pediatric dentist density and preventive dental care utilization by Medicaid-enrolled children. This model revealed that as the ratio of pediatric dentist per 10,000 children in a county increased by one, on average, the proportion of Medicaid-enrolled children who utilized preventive dental care increased by 0.79 percent. This was not a statistically significant increase (p=0.449). Multiple variable linear regression was performed to test the association between pediatric dentist density and preventive dental care utilization by Medicaid-enrolled children in a county, after adjusting for confounders (regionality and ABCD program age). After adjusting for those confounders, as the ratio of pediatric dentist per 10,000 children in a county increased by one, on average, the proportion of Medicaidenrolled children who utilized preventive dental care increased by 1.67 percent (p=0.047) (Table 2).
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DISCUSSION In this study, we examined the relationship between pediatric dentist density and preventive dental care utilization for Medicaid-enrolled children. Consistent with our hypothesis, the final regression model indicated pediatric dentist density is significantly and positively associated with preventive dental care use for Medicaid-enrolled children. Our findings are consistent with those of Groenewegen and Postma, who described a significant increase in use of dental services among publicly-insured patients corresponding to an increase in dentist density10. Their study was survey-based and evaluated dentist density and its effects on adult utilization of any dental service. The advantage of the present study compared to Groenewegen and Postma is that we analyzed administrative claims data, thus eliminating potential recall bias and sampling error.
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The two geographic regions of Washington State appear to influence both the density of pediatric dentist density and preventive dental care utilization for Medicaid-enrolled children. Regionality therefore was found to have a confounding effect in observing the relationship between these two variables (Figure 2). As expected, the more rural eastern part of Washington had overall lower pediatric dentist density. However, preventive dental care utilization in eastern Washington counties was higher compared to counties in western Washington. This unexpected result might be explained by the role extended family and community networks play in rural counties in helping families schedule dental appointments and find transportation to the dentist office. Families may be able to more easily find dentists who accept Medicaid because rural dentists have a more visible role in the community. Additionally, the importance of preventive dental care for children may be conveyed through social networks such as farm worker communities. Given the association between regionality and preventive dental service utilization we observed, future studies should identify regional characteristics such as the role of family and unique social networks that influence dental care utilization for socioeconomically vulnerable children in rural areas. We also found ABCD program age was significantly associated with pediatric dentist density and preventive dental utilization at the county level. ABCD was first rolled out in Spokane County in 1995 and was finished rolling out in 2013. Preliminary analyses indicate ABCD has been an effective strategy to improve access to dental care for younger children in Medicaid18. It is possible there are spillover effects to older children in Medicaid. Future research should examine the relationship between ABCD program age and dental utilization rates for Medicaid-enrolled children under age six years to help tailor interventions for vulnerable subgroups that could be layered onto the existing ABCD Program.
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These preliminary findings suggest that increasing the number of pediatric dentists in areas with high populations of Medicaid children may result in improvements in access to dental care services. However, this may not be a feasible workforce policy strategy given the cost of training pediatric dentists, who may not end up practicing in areas of high need. Other proposed solutions to improve access to care for vulnerable populations have included foreign trained dentists19,20, requiring a one-year residency after dental school21, or to introduce mid-level dental providers to target oral health disparities22. Such programs need
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to focus on providing additional training on how to treat children and deploying these providers to areas of need, including areas with no pediatric dentists. The current standard for measuring dental need is based on a dentist to population ratio. This measure is used to direct federal resources aimed at influencing the distribution of dentists to areas of higher need. The findings of the present study underscore the importance of developing area-level need measures that account for the specific dental needs of vulnerable children. Taking into account the pediatric dentist-to-child ratio in defining and allocating resources to areas of need could improve child dental care utilization rates.
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There are a number of study limitations. First, our model assumes patients do not travel across county lines for dental care. The county-level density measure may underestimate geographic access to pediatric dental care when the population lives near pediatric dentists in neighboring counties. Similarly, it is possible children could have lived in multiple counties in a given year. Additional geospatial analyses, which take into account distance to dentists, travel patterns, and changes in child residence, could provide additional insight on the role of dentist density and dental care use for Medicaid-enrolled children. Second, our models only consider a dentist’s primary place of practice, as reported by the WSAPD and verified through practice websites, and the Washington State Department Public Health and NPI registries. These data sources did not provide information on how dentists might split practice time between multiple practice locations. We were also unable to account for the number of years each dentist worked in a particular county. Measuring full-time equivalents rather than number of dentists would provide a more accurate estimate of the workforce availability. In future studies, surveying or interviewing pediatric dentists to better describe workplace characteristics could address this limitation. Third, our findings are generalizable only to children in Washington Medicaid. Care should be taken before applying our findings to other states because each state may have unique patterns of dental care utilization based on state Medicaid policies, population characteristics, and regional differences. This study does however serve as a model of the process by which similar analyses could be conducted in other states to determine the effects of pediatric dentist density on dental care use for children in Medicaid. Furthermore, the Patient Protection and Affordable Care Act will enroll thousands of new adults into Medicaid, which has unknown implications for dental utilization for children23. State and federal health policy reforms underscore the importance of additional research on ways to formulate workforce policies that will address disparities in dental use among publicly-insured populations. Finally, addressing disparities in preventive dental care utilization is only part of a comprehensive solution that includes improving oral health behaviors such as tooth brushing with fluoride toothpaste and reducing carbohydrate intake. Future studies should examine ways that Medicaid access interventions can address such health behaviors so that these interventions comprehensively improve oral health outcomes for vulnerable children.
CONCLUSION Based upon this study’s results, the following conclusions can be drawn:
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1.
After adjusting for confounders, there is a significant positive relationship between the number of pediatric dentists per 10,000 Medicaid-enrolled children and the proportion of Medicaid-enrolled children who utilized preventive dental care in a given year.
2.
Each additional pediatric dentist per 10,000 Medicaid-enrolled children in a county is associated with a 1.67 percent increase in utilization of preventive dental services for Medicaid-enrolled children.
3.
Policies aimed at improving pediatric oral health disparities should include strategies to increase the number of pediatric dentists who practice in counties with large numbers of Medicaid-enrolled children and provide additional training to non-specialists who treat children in these areas.
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ACKNOWLEDGEMENTS Thank you to the Washington State Health Care Authority for providing the Medicaid datasets, the Washington State Dental Service Foundation for data on the ABCD Program, and Ms. Stephanie Cook from the WSAPD for assistance with AAPD membership data. This study was funded by the National Institute of Dental and Craniofacial Research Grant No. K08DE020856 (D. Chi).
REFERENCES
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1. U.S. Department of Health and Human Services. Oral Health in America: A Report of the Surgeon General. Department of Health and Human Services, National Institute of Dental and Craniofacial Research, National Institutes of Health; Rockville, MD: 2000. 2. Macek MD, Heller KE, Selwitz RH, Manz MC. Is 75 percent of dental caries really found in 25 percent of the population? J Public Health Dent. 2004; 64:20–5. [PubMed: 15078057] 3. Filstrup SL, Briskie D, da Fonseca M, Lawrence L, Wandera A, Inglehart MR. Early childhood caries and quality of life: child and parent perspectives. Pediatr Dent n.d. 25:431–40. 4. Hollister MC, Weintraub JA. The association of oral status with systemic health, quality of life, and economic productivity. J Dent Educ. 1993; 57:901–12. [PubMed: 8263237] 5. United States. Government Accountability Office. Extent of Dental Disease in Children Has Not Decreased , and Millions Are Estimated to Have Untreated Tooth Decay. Government Accounting Office; Washington, DC: 2008. 6. Martin AB, Hardin JW, Veschusio C, Kirby HA. Differences in dental service utilization by rural children with and without participation in head start. Pediatr Dent. 2012; 34:107–11. [PubMed: 23211894] 7. Wang F, Luo W. Assessing spatial and nonspatial factors for healthcare access: towards an integrated approach to defining health professional shortage areas. Health Place. 2005; 11:131–46. [PubMed: 15629681] 8. Solomon E. Analysis of the Demographic Characteristics of Pediatric Dental Practice Sites. Pediatr Dent. 2007; 29:214–9. [PubMed: 17688018] 9. Nainar SMH, Feigal RJ. Geographic distribution of pediatric dentists in private practice in the United States. Pediatr Dent. 2004; 26:526–9. [PubMed: 15646916] 10. Groenewegen PP, Postma JH. The supply and utilization of dental services. Soc Sci Med. 1984; 19:451–9. [PubMed: 6484630] 11. Kaylor MB, Polivka BJ, Chaudry R, Salsberry P, Wee AG. Dental services utilization by women of childbearing age by socioeconomic status. J Community Health. 2010; 35:190–7. [PubMed: 20013059] 12. Dasanayake AP, Li Y, Philip S, Kirk K, Bronstein J, Childers NK. Utilization of dental sealants by Alabama Medicaid children: barriers in meeting the year 2010 objectives. Pediatr Dent n.d. 23:401–6.
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13. Chi D, Milgrom P. Preventive dental service utilization for Medicaid-enrolled children in New Hampshire: a comparison of care provided by pediatric dentists and general dentists. J Health Care Poor Underserved. 2009; 20:458–72. [PubMed: 19395842] 14. Wall TP, Brown LJ. The urban and rural distribution of dentists, 2000. J Am Dent Assoc. 2007; 138:1003–11. quiz 1023. [PubMed: 17606500] 15. Martin AB, Vyavaharkar M, Veschusio C, Kirby H. Rural-urban differences in dental service utilization among an early childhood population enrolled in South Carolina Medicaid. Matern Child Health J. 2012; 16:203–11. [PubMed: 21153760] 16. Rosenblatt RA, Andrilla CHA, Curtin T, Hart LG. Shortages of medical personnel at community health centers: implications for planned expansion. J Am Med Assoc. 2006; 295:1042–9. 17. Chi DL, Leroux B. County-level determinants of dental utilization for Medicaid-enrolled children with chronic conditions: How does place affect use? Health Place. 2012; 18:1422–9. [PubMed: 22981229] 18. Kobayashi M, Chi D, Coldwell SE, Domoto P, Milgrom P. The effectiveness and estimated costs of the access to baby and child dentistry program in Washington State. J Am Dent Assoc. 2005; 136:1257–63. [PubMed: 16196230] 19. Bazargan N, Chi DL, Milgrom P. Exploring the potential for foreign-trained dentists to address workforce shortages and improve access to dental care for vulnerable populations in the United States: a case study from Washington State. BMC Health Serv Res. 2010; 10:336. [PubMed: 21143987] 20. Mick SS, Lee SY, Wodchis WP. Variations in geographical distribution of foreign and domestically trained physicians in the United States: “safety nets” or “surplus exacerbation”? Soc Sci Med. 2000; 50:185–202. [PubMed: 10619689] 21. Lamster IB, Eaves K. A model for dental practice in the 21st century. Am J Public Health. 2011; 101:1825–30. [PubMed: 21852631] 22. Friedman JW, Mathu-Muju KR. Dental therapists: improving access to oral health care for underserved children. Am J Public Health. 2014; 104:1005–9. [PubMed: 24825199] 23. Dubay L, Kenney G. Expanding Public Health Insurance to Parents: Effects on Children’s Coverage under Medicaid. Health Serv Res. 2003; 38:1283–302. [PubMed: 14596391]
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Preventive Dental Care Utilization for Medicaid- enrolled Children in Washington State by County, 2012. (B) Pediatric Dentist Density in Washington State by county, 2012
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Dental care utilization and pediatric dentist density, comparing eastern and western Washington State counties, 2012
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Table 1
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Unadjusted associations between proposed confounders with pediatric dentist density and preventive dental services utilization among Medicaid-enrolled children in Washington State in 2012 (n = 39) using linear regression. Pediatric Dentist Density
Preventive Dental Services
Variable:
Slope
P-value
Slope
P-value
General dentist-to-child ratio
0.08
0.014*
−0.09
0.613
Number of community health centers
0.19
0.002*
0.39
0.290
Dental Health Professional Shortage Area designation
0.075
No part of county a shortage area
0.117
(reference)
(reference)
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Whole county a shortage area
−3.15
0.113
−3.18
0.766
Part of county a shortage area
−2.50
0.196
4.93
0.632
< 0.001*
Rural-Urban Continuum Codes 1 - 3 (metropolitan) (reference) 4 – 6 (nonmetropolitan) 7 – 9 (rural) Access to Baby and Child Dentistry Program age
0.201
(reference)
(reference)
−2.36
< 0.001*
−5.07
0.168
−2.72
< 0.001*
−7.38
0.115
0.19
0.005*
1.02
0.009* 0.001*
Regionality western Washington
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eastern Washington
(reference) −1.60
0.006*
(reference) 10.30
0.001*
*
p
