In this critical review, we summarized the evidence on associations between individual/household income and oral health, between income inequality and oral health, and income-related inequalities in oral health. Meta-analyses of mainly cross-sectional studies confirm that low individual/household income is associated with oral cancer (odds ratio, 2.41; 95% confidence interval [CI], 1.59–3.65), dental caries prevalence (prevalence ratio, 1.29; 95% CI, 1.18–1.41), any caries experience (odds ratio, 1.40; 95% CI, 1.19–1.65), tooth loss (odds ratio, 1.66; 95% CI, 1.48–1.86), and traumatic dental injuries (odds ratio, 0.76; 95% CI, 0.65–0.89). Reviews also confirm qualitatively that low income is associated with periodontal disease and poor oral health–related quality of life. Limited evidence from the United States shows that psychosocial and behavioral explanations only partially explain associations between low individual/household income and oral health. Few country-level studies and a handful of subnational studies from the United States, Japan, and Brazil show associations between area-level income inequality and poor oral health. However, this evidence is conflicting given that the association between area-level income inequality and oral health outcomes varies considerably by contexts and by oral health outcomes. Evidence also shows cross-national variations in income-related inequalities in oral health outcomes of self-rated oral health, dental care, oral health–related quality of life, outcomes of dental caries, and outcomes of tooth loss. There is a lack of discussion in oral health literature about limitations of using income as a measure of social position. Future studies on the relationship between income and oral health can benefit substantially from recent theoretical and methodological advancements in social epidemiology that include application of an intersectionality framework, improvements in reporting of inequality, and causal modeling approaches. Theoretically well-informed studies that apply robust epidemiological methods are required to address knowledge gaps for designing relevant policy interventions to reduce income-related inequalities in oral health.
AidaJKondoKKondoNWattRGSheihamATsakosG.2011. Income inequality, social capital and self-rated health and dental status in older Japanese. Soc Sci Med. 73(10):1561–1568.
2.
BartleyM.2004. Health inequality: an introduction to theories, concepts, and methods. Cambridge, UK: Polity.
3.
BastosJLBoingAFPeresKGAntunesJLPeresMA.2011. Periodontal outcomes and social, racial and gender inequalities in Brazil: a systematic review of the literature between 1999 and 2008. Cad Saude Publica. 27(Suppl 2):S141–S153.
4.
Ben-ShlomoYKuhD.2002. A life course approach to chronic disease epidemiology: conceptual models, empirical challenges and interdisciplinary perspectives. Int J Epidemiol. 31(2):285–293.
5.
BernabeEHobdellMH.2010. Is income inequality related to childhood dental caries in rich countries?J Am Dent Assoc. 141(2):143–149.
6.
BernabeEMarcenesW.2011. Income inequality and tooth loss in the United States. J Dent Res. 90(6):724–729.
7.
BernabeESheihamASabbahW.2009. Income, income inequality, dental caries and dental care levels: an ecological study in rich countries. Caries Res. 43(4):294–301.
8.
BhandariBNewtonJTBernabeE.2015a. Income inequality and use of dental services in 66 countries. J Dent Res. 94(8):1048–1054.
9.
BhandariBNewtonJTBernabeE.2015b. Income inequality, disinvestment in health care and use of dental services. J Public Health Dent. 75(1):58–63.
10.
BlakelyTDisneyGAtkinsonJTengAMackenbachJP.2017. A typology for charting socioeconomic mortality gradients: “go southwest.” Epidemiology. 28(4):594–603.
11.
BlakelyTDisneyGValeriLAtkinsonJTengAWilsonNGurrinL.2018. Socioeconomic and tobacco mediation of ethnic inequalities in mortality over time: repeated census-mortality cohort studies, 1981 to 2011. Epidemiology. 29(4):506–516.
12.
BorrellLNCrawfordND.2012. Socioeconomic position indicators and periodontitis: examining the evidence. Periodontol 2000. 58(1):69–83.
13.
BorrellLNTalihM.2012. Examining periodontal disease disparities among U.S. adults 20 years of age and older: NHANES III (1988–1994) and NHANES 1999–2004. Public Health Rep. 127(5):497–506.
14.
CelesteRKFritzellJNadanovskyP.2011. The relationship between levels of income inequality and dental caries and periodontal diseases. Cad Saude Publica. 27(6):1111–1120.
15.
CelesteRKNadanovskyP.2010. How much of the income inequality effect can be explained by public policy? Evidence from oral health in Brazil. Health Policy. 97(2–3):250–258.
16.
CelesteRKNadanovskyPFritzellJ.2011. Trends in socioeconomic disparities in the utilization of dental care in Brazil and Sweden. Scand J Public Health. 39(6):640–648.
17.
CelesteRKNadanovskyPPonce de LeonAFritzellJ.2009. The individual and contextual pathways between oral health and income inequality in Brazilian adolescents and adults. Soc Sci Med. 69(10):1468–1475.
18.
ChalubLLBorgesCMFerreiraRCHaddadJPFerreiraEFEVargasAM.2014. Association between social determinants of health and functional dentition in 35-year-old to 44-year-old Brazilian adults: a population-based analytical study. Community Dent Oral Epidemiol. 42(6):503–516.
19.
ChalubLLMartinsCCFerreiraRCVargasAM.2016. Functional dentition in Brazilian adults: an investigation of social determinants of health (SDH) using a multilevel approach. PLoS One. 11(2):e0148859.
20.
Commission on Social Determinants of Health. 2007. A conceptual framework for action on the social determinants of health. Geneva, Switzerland: World Health Organization.
21.
ConwayDIPetticrewMMarlboroughHBerthillerJHashibeMMacphersonLM.2008. Socioeconomic inequalities and oral cancer risk: a systematic review and meta-analysis of case-control studies. Int J Cancer. 122(12):2811–2819.
22.
Correa-FariaPMartinsCCBoneckerMPaivaSMRamos-JorgeMLPordeusIA.2015. Absence of an association between socioeconomic indicators and traumatic dental injury: a systematic review and meta-analysis. Dent Traumatol. 31(4):255–266.
23.
DalyMCDuncanGJMcDonoughPWilliamsDR.2002. Optimal indicators of socioeconomic status for health research. Am J Public Health. 92(7):1151–1157.
24.
DoLGSpencerAJSladeGDHaDHRoberts-ThomsonKFLiuP.2010. Trend of income-related inequality of child oral health in Australia. J Dent Res. 89(9):959–964.
25.
EvansCRWilliamsDROnnelaJPSubramanianSV.2018. A multilevel approach to modeling health inequalities at the intersection of multiple social identities. Soc Sci Med. 203:64–73.
26.
FarmerJMcLeodLSiddiqiARavaghiVQuinonezC.2016. Towards an understanding of the structural determinants of oral health inequalities: a comparative analysis between Canada and the United States. SSM Popul Health. 2:226–236.
27.
FarmerJPhillipsRCSinghalSQuinonezC.2017. Inequalities in oral health: understanding the contributions of education and income. Can J Public Health. 108(3):e240–e245.
28.
FleischerNLDiez RouxAV.2008. Using directed acyclic graphs to guide analyses of neighbourhood health effects: an introduction. J Epidemiol Community Health. 62(9):842–846.
29.
GalobardesBShawMLawlorDALynchJWDavey SmithG.2006. Indicators of socioeconomic position (part 1). J Epidemiol Community Health. 60(1):7–12.
30.
Goulart MdeAVettoreMV.2016. Is the relative increase in income inequality related to tooth loss in middle-aged adults?J Public Health Dent. 76(1):65–75.
31.
Guarnizo-HerreñoCCTsakosGSheihamAMarmotMGKawachiIWattRG.2015. Austin Powers bites back: a cross sectional comparison of US and English national oral health surveys. BMJ. 351:h6543.
32.
HeadeyB.2008. Poverty is low consumption and low wealth, not just low income. Soc Indic Res. 89(1):23–39.
KapilashramiAHankivskyO.2018. Intersectionality and why it matters to global health. Lancet. 391(10140):2589–2591.
35.
KassebaumNJSmithAGCBernabéEFlemingTDReynoldsAEVosTMurrayCJLMarcenesW; GBD 2015 Oral Health Collaborators. 2017. Global, regional, and national prevalence, incidence, and disability-adjusted life years for oral conditions for 195 countries, 1990–2015: a systematic analysis for the global burden of diseases, injuries, and risk factors. J Dent Res. 96(4):380–387.
36.
KawachiIKennedyBP.1999. Income inequality and health: pathways and mechanisms. Health Serv Res. 34(1Pt 2):215–227.
37.
KjellssonGGerdthamUGPetrieD.2015. Lies, damned lies, and health inequality measurements: understanding the value judgments. Epidemiology. 26(5):673–680.
38.
KramerPFChaffeeBWBertelliAEFerreiraSHBeriaJUFeldensCA.2015. Gains in children’s dental health differ by socioeconomic position: evidence of widening inequalities in southern Brazil. Int J Paediatr Dent. 25(6):383–392.
39.
KumarSKroonJLallooR.2014. A systematic review of the impact of parental socio-economic status and home environment characteristics on children’s oral health related quality of life. Health Qual Life Outcomes. 12:41.
40.
LaaksonenMPrättäläRHelasojaVUutelaALahelmaE.2003. Income and health behaviours: evidence from monitoring surveys among Finnish adults. J Epidemiol Community Health. 57(9):711–717.
41.
LynchJSmithGDHarperSHillemeierMRossNKaplanGAWolfsonM.2004. Is income inequality a determinant of population health? Part 1. A systematic review. Milbank Q. 82(1):5–99.
42.
LynchJWKaplanGASalonenJT.1997. Why do poor people behave poorly? Variation in adult health behaviours and psychosocial characteristics by stages of the socioeconomic lifecourse. Soc Sci Med. 44(6):809–819.
43.
MacIntyreS.1997. The Black report and beyond: what are the issues?Soc Sci Med. 44(6):723–745.
44.
MackenbachJPMartikainenPMenvielleGde GelderR.2016. The arithmetic of reducing relative and absolute inequalities in health: a theoretical analysis illustrated with European mortality data. J Epidemiol Community Health. 70(7):730–736.
45.
ManskiRMoellerJChenHWidstromEListlS.2016. Disparity in dental attendance among older adult populations: a comparative analysis across selected European countries and the USA. Int Dent J. 66(1):36–48.
46.
MejiaGJamiesonLMHaDSpencerAJ.2014. Greater inequalities in dental treatment than in disease experience. J Dent Res. 93(10):966–971.
47.
MerloJ.2018. Multilevel analysis of individual heterogeneity and discriminatory accuracy (MAIHDA) within an intersectional framework. Soc Sci Med. 203:74–80.
48.
MoellerJStarkelRQuiñonezCVujicicM.2017. Income inequality in the United States and its potential effect on oral health. J Am Dent Assoc. 148(6):361–368.
49.
NandiAGlymourMMKawachiIVanderWeeleTJ.2012. Using marginal structural models to estimate the direct effect of adverse childhood social conditions on onset of heart disease, diabetes, and stroke. Epidemiology. 23(2):223–232.
50.
PattussiMPMarcenesWCroucherRSheihamA.2001. Social deprivation, income inequality, social cohesion and dental caries in Brazilian school children. Soc Sci Med. 53(7):915–925.
51.
PeresMALiuPDemarcoFFSilvaAERWehrmeisterFCMenezesAMPeresKG.2018. Income trajectories affect treatment of dental caries from childhood to young adulthood: a birth cohort study. Braz Oral Res. 32:e36.
52.
PeresMALuzziLPeresKGSabbahWAntunesJLDoLG.2015. Income-related inequalities in inadequate dentition over time in Australia, Brazil and USA adults. Community Dent Oral Epidemiol. 43(3):217–225.
53.
PeresMAPeresKGAntunesJLJunqueiraSRFrazaoPNarvaiPC.2003. The association between socioeconomic development at the town level and the distribution of dental caries in Brazilian children. Rev Panam Salud Publica. 14(3):149–157.
54.
PeresMAPeresKGde BarrosAJDVictoraCG.2007. The relation between family socioeconomic trajectories from childhood to adolescence and dental caries and associated oral behaviours. J Epidemiol Community Health. 61(2):141–145.
55.
RavaghiVQuinonezCAllisonPJ.2013a. Comparing inequalities in oral and general health: findings of the Canadian health measures survey. Can J Public Health. 104(7):e466–e471.
56.
RavaghiVQuinonezCAllisonPJ.2013b. The magnitude of oral health inequalities in Canada: findings of the Canadian health measures survey. Community Dent Oral Epidemiol. 41(6):490–498.
57.
RoncalliAGSheihamATsakosGWattRG.2015. Socially unequal improvements in dental caries levels in Brazilian adolescents between 2003 and 2010. Community Dent Oral Epidemiol. 43(4):317–324.
58.
SabbahWSheihamABernabeE.2010. Income inequality and periodontal diseases in rich countries: an ecological cross-sectional study. Int Dent J. 60(5):370–374.
59.
SabbahWTsakosGChandolaTSheihamAWattRG.2007. Social gradients in oral and general health. J Dent Res. 86(10):992–996.
60.
SabbahWTsakosGSheihamAWattRG.2009. The role of health-related behaviors in the socioeconomic disparities in oral health. Soc Sci Med. 68(2):298–303.
61.
SabbahWWattRGSheihamATsakosG.2009. The role of cognitive ability in socio-economic inequalities in oral health. J Dent Res. 88(4):351–355.
62.
SandersAESladeGDJohnMTSteeleJGSuominen-TaipaleALLahtiSNuttallNMAllenPF.2009. A cross-national comparison of income gradients in oral health quality of life in four welfare states: application of the Korpi and Palme typology. J Epidemiol Community Health. 63(7):569–574.
63.
SchuchHSNascimentoGGPeresKGMittintyMNDemarcoFFCorreaMBGiganteDPHortaBLPeresMADoLG.2019. The controlled direct effect of early life socioeconomic position on periodontitis in a birth cohort. Am J Epidemiol. 188(6):1101–1108.
64.
SchuchHSPeresKGDemarcoFFHortaBLGiganteDPPeresMADoLG.2018. Effect of life-course family income trajectories on periodontitis: birth cohort study. J Clin Periodontol. 45(4):394–403.
65.
SchuchHSPeresKGSinghAPeresMADoLG.2017. Socioeconomic position during life and periodontitis in adulthood: a systematic review. Community Dent Oral Epidemiol. 45(3):201–208.
66.
SchwendickeFDorferCESchlattmannPFoster PageLThomsonWMParisS.2015. Socioeconomic inequality and caries: a systematic review and meta-analysis. J Dent Res. 94(1):10–18.
67.
SeerigLMNascimentoGGPeresMAHortaBLDemarcoFF.2015. Tooth loss in adults and income: systematic review and meta-analysis. J Dent. 43(9):1051–1059.
68.
ShenJWildmanJSteeleJ.2013. Measuring and decomposing oral health inequalities in an UK population. Community Dent Oral Epidemiol. 41(6):481–489.
69.
SinghAHarfordJAntunesJLFPeresMA.2018. Area-level income inequality and oral health among Australian adults—a population-based multilevel study. PLoS One. 13(1):e0191438.
70.
SinghAHarfordJSchuchHSWattRGPeresMA.2016. Theoretical basis and explanation for the relationship between area-level social inequalities and population oral health outcomes: a scoping review. SSM Popul Health. 2:451–462.
71.
SissonKL.2007. Theoretical explanations for social inequalities in oral health. Community Dent Oral Epidemiol. 35(2):81–88.
72.
SladeGDAkinkugbeAASandersAE.2014. Projections of U.S. edentulism prevalence following 5 decades of decline. J Dent Res. 93(10):959–965.
73.
SubramanianSVJonesKKaddourAKriegerN.2009. Revisiting Robinson: the perils of individualistic and ecologic fallacy. Int J Epidemiol. 38(2):342–360; author reply 370–343.
74.
TchicayaALorentzN.2014. Socioeconomic inequalities in the non-use of dental care in Europe. Int J Equity Health. 13:7.
75.
TownsendPDavidsonNBlackDS.1982. Inequalities in health: the Black Report. Harmondsworth, UK: Penguin.
76.
VanderWeeleTJ.2015. Explanation in causal inference: methods for mediation and interaction. New York, NY: Oxford University Press.
77.
van DoorslaerEMasseriaCKoolmanX; The OECD Health Equity Research Group. 2006. Inequalities in access to medical care by income in developed countries. Can Med Assoc J. 174(2):177–183.
78.
VettoreMVAqeeliA.2016. The roles of contextual and individual social determinants of oral health-related quality of life in Brazilian adults. Qual Life Res. 25(4):1029–1042.
79.
VettoreMVMarquesRAPeresMA.2013. Social inequalities and periodontal disease: multilevel approach in SBBrasil 2010 survey. Rev Saude Publica. 47(Suppl 3):29–39.
80.
WagstaffADoorslaerE.V.2000. Income inequality and health: what does the literature tell us?Annu Rev Public Health. 21:543–567.
81.
WattRGHeilmannAListlSPeresMA.2016. London charter on oral health inequalities. J Dent Res. 95(3):245–247.
82.
WattRGSheihamA.2012. Integrating the common risk factor approach into a social determinants framework. Community Dent Oral Epidemiol. 40(4):289–296.
Supplementary Material
Please find the following supplemental material available below.
For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.
For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.
