Universal coverage for oral health care in 27 low-income countries: a scoping review

Background Low-income countries bear a growing and disproportionate burden of oral diseases. With the World Health Organization targeting universal oral health coverage by 2030, assessing the state of oral health coverage in these resource-limited nations becomes crucial. This research seeks to examine the political and resource commitments to oral health, along with the utilization rate of oral health services, across 27 low-income countries. Methods We investigated five aspects of oral health coverage in low-income countries, including the integration of oral health in national health policies, covered oral health services, utilization rates, expenditures, and the number of oral health professionals. A comprehensive search was conducted across seven bibliographic databases, three grey literature databases, and national governments’ and international organizations’ websites up to May 2023, with no linguistic restrictions. Countries were categorized into “full integration”, “partial integration”, or “no integration” based on the presence of dedicated oral health policies and the frequency of oral health mentions. Covered oral health services, utilization rates, expenditure trends, and the density of oral health professionals were analyzed using evidence from reviews and data from World Health Organization databases. Results A total of 4242 peer-reviewed and 3345 grey literature texts were screened, yielding 12 and 84 files respectively to be included in the final review. Nine countries belong to “full integration” and thirteen countries belong to “partial integration”, while five countries belong to “no integration”. Twelve countries collectively covered 26 types of oral health care services, with tooth extraction being the most prevalent service. Preventive and public health-based oral health interventions were scarce. Utilization rates remained low, with the primary motivation for seeking care being dental pain relief. Expenditures on oral health were minimal, predominantly relying on domestic private sources. On average, the 27 low-income countries had 0.51 dentists per 10,000 population, contrasting with 2.83 and 7.62 in middle-income and high-income countries. Conclusions Oral health care received little political and resource commitment toward achieving universal health coverage in low-income countries. Urgent action is needed to mobilize financial and human resources, and integrate preventive and public health-based interventions. Supplementary Information The online version contains supplementary material available at 10.1186/s41256-024-00376-9.


Introduction
Oral diseases, such as dental caries, periodontal disease, and oral cancer, stand out as the most prevalent health conditions, posing a major global public health challenge [1].It was estimated that approximately 3.5 billion people suffered from oral diseases worldwide [2].Oral diseases could lead to pain, swelling, mastication difficulties, and susceptibility to other medical conditions such as atherosclerosis, cardiovascular disease, diabetes, and malnutrition [3][4][5][6].Oral diseases can also affect self-esteem, reduce social interaction, and even result in stigmatization [7].Moreover, they are closely linked to substantial productivity loss and lower educational attainments.Evidence indicates that the global productivity loss due to oral diseases reached an estimated US$ 323 billion in 2019 [7]; additionally, children with poor oral health are 52% more likely to exhibit poor academic performance and 43% more likely to experience school absenteeism [8].
Resources for oral health care and the burden of oral diseases are unevenly distributed across regions, countries, and socioeconomic groups [7].In 2019, 88% of the direct costs of oral health care were spent for only 22.5% of the world's population, mainly residing in high-income countries [7].Meanwhile, more than three-quarters of those with oral conditions lived in low-and middleincome countries (LMICs) [7].In Rwanda, for example, 54.3% of its population had untreated dental caries according to its first National Oral Health Survey [9].Due to high out-of-pocket spending, disadvantaged households paying for necessary oral health care are more likely to experience catastrophic health expenditures and face impoverishment than their better-off counterparts [10,11].In addition, countries with public dental care coverage have lower socioeconomic inequalities in dental care utilization than those without such programs [12].
To tackle these challenges, the global community has launched a series of initiatives for oral health.In 2021, the World Health Assembly (WHA) adopted a resolution urging the integration of oral health into national policies and universal health coverage (UHC) [13].This resolution was followed by the release of the Global Strategy on Oral Health during the 2022 WHA, which envisions achieving UHC for oral health for all individuals and communities by 2030 [14].As a critical step towards implementing this strategy, the World Health Organization (WHO) released the Global Oral Health Action Plan (2023-2030), providing guidance for member states to operationalize objectives at the national and sub-national levels [15].On December 15, 2023, the WHO added Noma (Cancrum Oris) to its list of neglected tropical diseases, marking a significant step toward prioritizing political and resource commitments for this severe and potentially fatal oral disease [16].
In addition to these initiatives, a notable effort is the WHO Global Oral Health Status Report [7].This report reviews the status of oral disease burden, oral health policies, and resource investments over countries.While groundbreaking, the report and its country profiles only provide a summary of the existence of national oral health policies using a binary "yes-or-no" question without providing further details, such as the covered oral health services in their national policies.In addition, the report does not examine oral health service utilization rates or analyze oral health expenditures over the years.
To address these gaps, especially for low-income countries, we conducted a scoping review to examine universal oral health coverage in low-income countries through five key questions: (1) the integration of oral health in national health policies; (2) the inclusion of clinical and public oral health care services in government-defined essential health service lists; (3) oral health care utilization rates; (4) oral health care expenditures; and (5) the number of oral health care professionals.

Search strategy
We conducted a scoping review to examine the universal coverage for oral health care in low-income countries.We followed the World Bank 2020 income classification [17] in identifying the 27 low-income countries (countries with gross national income [GNI] per capita of 1,045 US dollars or less) as listed in Table 1.We looked for evidence from peer-reviewed publications, grey literature, websites of national governments and international organizations, and WHO databases.We reported this scoping review in accordance with the guidance of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) [18].We registered the protocol of this scoping review a priori in Open Science Framework (https:// osf.io/ 5pbhm/).For peer-reviewed publications, we systematically searched seven bibliographic electronic databases: Pub-Med, Embase (Elsevier), Web of Science (Clarivate), EconLit (EBSCO), Global Health (EBSCO), WHO Global     2, the string consists of three groups of keywords: keywords and MeSH terms representing "oral", "dental", and "teeth"; keywords representing health care or the three UHC dimensions, such as "care", "health", "service", "finance", "coverage", "spending", "utilization"; and keywords and MeSH terms referring to the 27 low-income countries.We searched for the presence of keywords in titles and abstracts of publications.The search covered the period from January 2010 to May 2023 to capture the recent data.
We conducted a comprehensive search for grey literature from four sources.First, we searched the WHO Country Planning Cycle Database [19], WHO Noncommunicable Diseases Document Repository [20], and WHO MiNDbank database [21] to identify countries' most recent National Health Policies, Strategies, and Plans (NHPSPs), National Health Service Packages, National Non-communicable Disease Strategic Plans, and National Oral Health Strategic Plans.A NHPSP outlines a country's political and resource commitment to ensuring the health of its population [22], while a National Health Service Package specifies governmentdefined essential public and clinical health services to be delivered at different health care levels [23].By examining National Non-communicable Disease Strategic Plans, we assessed the extent to which countries align with WHO's recommendations on recognizing and addressing oral health issues through the lens of common risk factors shared with other non-communicable diseases.
Additionally, through searching National Oral Health Strategic Plans, we provided baseline information on the progress toward the international commitment of having operational national oral health policies by 2030 [15].
Second, we conducted searches to identify oral health content in national health policies beyond the four policy types mentioned above.This was done by using the WHO publication database [24] and the Google search engine with predefined strings.The Google search was applied to the websites of national health departments and WHO country profiles [25] (see details for the Google search in Web Appendix 2).Third, we searched three grey literature databases, including the PAIS Index, OECD iLibrary, and World Bank eLibrary (see details in Web Appendix 3).Both Google and grey literature database searches covered the period from January 2010 to May 2023.Fourth, we examined the websites and reports of major non-governmental organizations and foundations that provide international oral health care services, such as Global Dental Relief [26], Smiles for Everyone Foundation [27], and Global Child Dental Fund [28].We utilized a snowball strategy to scrutinize the reference lists of searched peer-reviewed and grey literature.

Literature review and evidence extraction
For peer-reviewed publications, titles and abstracts of searched studies were imported into reference management tools (EndNote and Zotero).Duplicates were removed.All remaining titles and abstracts were uploaded to the Covidence platform (https:// www.covid ence.org/), where three coauthors independently screened and selected studies for full-text review.The selected full-text studies were subsequently retrieved and assigned to two groups of coauthors for data extraction, with each group consisting of two members.To ensure accuracy, the two coauthors of each group independently reviewed the same studies and cross-checked each other's work.For grey literature, as most of it does not have a structured abstract, we were not able to remove duplicates with reference management tools.Therefore, we assigned the full text of all the searched grey literature to four groups of coauthors, with each group consisting of two members, to conduct a literature review and data extraction in duplicate.
We used a pilot-tested template in the form of Excel spreadsheets to record the extracted information.This template included fields for "title", "author(s)", "publication year", "study location", "study design", "study aim", "data source", "data collected year", and "main findings".Discrepancies between group members on review and data extraction were discussed and addressed at team meetings.Additional details on data extraction can be found in Web Appendix 4.

Evidence synthesis and analysis
We started with assessing a country's integration of oral health into national health policies.We categorized the 27 low-income countries into three groups: first, "full integration", defined as countries that have developed national oral health policies, thereby fulfilling target 1.1 of the WHO Global Oral Health Action Plan (2023-2030) related to establishing operational national oral health policies [15]; second, "partial integration", defined as countries that lack such specific policies but aggregately mention oral health keywords at least five times across other national health policies; and third, "no integration", defined as countries that lack national oral health policies and aggregately mention oral health keywords less than five times across other national health policies.In order to identify countries as "partial integration" and "no integration", we followed previous studies [29,30] and created a list of oral health keywords through a review of significant literature on oral health.We conducted searches for each keyword and counted the frequency of their appearance in each included national health policy document.We only counted when a keyword appeared in the context of oral health.For example, the keyword "abscess" will be counted if it pertains to dental abscesses but will not be counted if it refers to abscesses within other tissues of the body (see keywords in Web Appendix 5).The threshold of at least five mentions was established as a significant number in previous studies that assessed the policy inclusion of surgery [29,30].Since countries' NHPSPs and National Noncommunicable Disease Strategic Plans are the main policies demonstrating countries' political commitments to health, we also offered a more detailed summary of oral health content within these two policy types, which is presented in the Appendix.
In terms of assessing oral health services included in countries' essential service packages, we focused on the national health policies that include a list of governmentdefined essential clinical and public health services, such as National Health Service Packages, and summarized the covered oral health care services.This analysis aimed to provide insights into the extent to which oral health has received practical priority within essential healthcare coverages outlined in national policies.
To assess oral health care utilization rates, we narratively summarized utilization rates found in both peerreviewed publications and grey literature.Additionally, we summarized the primary reasons for seeking oral health care services and the most frequently administered interventions.We also summarized the determinants and inequalities of oral health care utilizations.
We used two international data sources to assess oral health expenditures: (1) the WHO Global Oral Health Status country profiles [31], which documented per capita expenditures on outpatient dental care in 2019, aggregated from both public and private sources, and (2) the WHO Global Health Expenditure Database [32], which recorded dental outpatient expenditures per capita financed by domestic public, private, and external sources between 2016 and 2020.We downloaded data from these two sources in May 2023.We identified thirteen low-income countries with available data from both data sources and compared their recorded values.
To assess the workforce, we obtained data on the number of dentists, dental prosthetic technicians, dental assistants and dental therapists per 10,000 population from the WHO National Health Workforce Account [33].We downloaded data for the years spanning from 2010 and 2021.Countries varied in terms of years with available data.Using countries' most recent data, we calculated the average densities of dentists, dental prosthetic technicians, dental assistants and dental therapists in low-income countries and compared them with those in middle-income and high-income countries.We downloaded the workforce data in July 2023.
Web Appendix 6 presents a summary of the information sources used to gather evidence for analyzing each of the five research questions.

Results
As shown in the PRISMA flowchart (Fig. 1), our systematic search of the seven electronic bibliographic databases yielded a total of 4242 studies.After removing duplicates, studies published before 2010, and those deemed irrelevant based on title and abstract screening, a fulltext review for eligibility was given to 65 studies.From this full-text review, we identified twelve peer-reviewed papers that met our inclusion criteria.For grey literature, we obtained 3345 records from multiple sources.After a full-text review of each literature, we excluded 3241 records that did not meet the inclusion criteria, as well as 20 outdated policies that had been replaced by their more recent versions.Consequently, we included 84 pieces of grey literature.Together with the peer-reviewed studies, our scoping review ultimately included 96 articles.For the twelve peer-reviewed papers, Table 3 demonstrates that nine out of them are questionnaire-and screening-based research that provided information on oral health care utilization, while three discussed the current stock or the development of oral health professionals.Out of the 84 pieces of grey literature, 28 consist of the WHO Global Oral Health Status Report and its associated country profiles, while the remaining 56 comprise the most recent national health policies with oral health care information.Figure 3 illustrates that the 56 national

Oral health care services included in government-defined essential health service lists
We identified thirteen countries with lists of governmentdefined essential clinical and public health care services.Except Burundi, all the other twelve countries mentioned the coverage of oral health care services, resulting in a collective offering of 26 different types of oral health care services (Table 4).By country, Rwanda distinguished itself by offering the most extensive array of oral services to its population (12 types) [52][53][54].It is followed by Ethiopia (11 types) [73], Sierra Leone (8 types) [81], Liberia (5 types) [79], Madagascar and Mozambique (4 types, respectively) [40,45], Afghanistan, Malawi, and Somalia (3 types, respectively) [59,80,83], Eritrea (2 types) [71], as well as Gambia and Sudan (1 type, respectively) [76,88].
Tooth extraction emerged as the predominant intervention, appearing in the health service lists of seven countries [40,52,73,[79][80][81]83]. Four countries covered dental abscess drainage [52,73,79,83], making this procedure the second most frequently provided intervention.In contrast, as preventive measures, services on oral health knowledge awareness [45,73,81], dental scaling [54], fluoride use expansion [45], and     oral disease screening [53] were only covered by a small number of countries.Of particular concern, only Sierra Leone explicitly covered Atraumatic Restorative Treatment (also called Alternative Restorative Treatment) (ART) [81].As ART has been recommended by the WHO as a cost-effective approach to address dental caries in resource-limited settings [23,90], its rare coverage indicates a consistently insufficient supply in lowincome countries.Additionally, information was limited regarding what segment of the population was covered by essential oral health care services.We identified only four countries with explicit information on the age characteristics of the covered population, including Liberia [79], Mozambique [45], and Eritrea [71], covering oral health care services for school-age children; only Eritrea and Ethiopia, however, explicitly covered oral health care services for the elderly and the detection of cleft lip and palate for newborns, respectively [71,73].Information was scarce regarding the cost-sharing structure of oral health care services.Among the countries that included coverage of oral health care services, only Ethiopia explicitly outlined a cost-sharing arrangement.In Ethiopia, the detection of cleft lip and palate in newborns, along with the promotion of awareness regarding proper oral hygiene practices, is provided at no cost.However, other oral health care services, such as tooth extraction, involve a cost-sharing mechanism [73].Unfortunately, detailed information on the specifics of the cost-sharing mechanism is lacking.

Utilization rates of oral health care service
We identified seven countries with available information on the utilization rates of oral health care services.
Among countries with nationally sampled populations, the individual rate was 2.0% in Mozambique among its general population (past 12 months usage) [46], 2.1% in Burkina Faso among adults (past 6 months usage) [91], 13.4% in Sudan among adults (past 12 months usage) [92], and 29.4% in Rwanda among its general population (ever usage) [9]; Sierra Leone witnessed various utilization rates of ever usage for school children at different ages, ranging from 3.0% for the 6-years-old, 34.0% for the 12-years-old, to 27.0% for the 15-years-old [93].On the other hand, for populations sampled at the subnational or institutional level, the estimated rates ranged from 7.4% in Ethiopia's Areka town among school children (past 12 months usage) [94], 10.6% in Ethiopia's Mekelle city among school children (past 12 months usage) [95], 9.0% in Sudan's Khartoum State among aged 16 and above for regular checkups and 37% among the elderly attending primary healthcare centers (past 12 months usage) [96,97], to 52.0% in Uganda's Nebbi District among adults (past 12 months usage) [98].
In terms of reasons for seeking oral health care services, a significant proportion of the surveyed population reported dental pain, such as 66.9% in Sudan and 98.7% in Rwanda [9,92], or reported that they would only seek care when facing oral health conditions (e.g., school children in Sierra Leone) [93].In the realm of treatments, tooth extraction was the most frequently administered intervention for alleviating dental pain, rather than other restorative dental care procedures.Concretely, among the individuals who sought oral health care services, 73.7% of those in Uganda's Nebbi District had tooth extraction as their sole treatment [98], while the percentage was 55.0% in Sudan's Khartoum State [97], and 52.0% in Mozambique [46].In Ethiopia's Areka town, 41.4% of those who have visited dental clinics went for emergency dental pain treatment and 8.6% for tooth extraction [94].See details in Table 3 and Web Appendix 7.
We identified three peer-reviewed papers with information on the determinants and inequalities of dental service utilization.Among the socioeconomic determinants, adults residing in urban areas, those from wealthier households, or school children born to mothers with higher educational attainment are consistently more likely to use dental care services compared to those living in rural areas, from less wealthy households, or children born to mothers with lower education levels [91,92,95].

Oral health care expenditures
Oral healthcare expenditures in low-income countries are low.Based on WHO's Global Oral Health Status country profiles [31], only North Korea, the Syrian Arab Republic, and Sudan allocated more than one US dollar per capita in 2019 on dental outpatient care, while all the other countries spent an amount ranging from zero to 0.5 US dollars per capita (Fig. 4).On the other hand, according to the WHO Global Health Expenditure Database [32], fourteen countries spent an average of 0.19 US dollars per capita for dental outpatient care for the most recent year of available data.Among these fourteen countries, nine predominantly relied on the domestic private sector to bear expenditures, with only Afghanistan, Gambia, and South Sudan financing more than half of Table 4 Oral health care services included in government-defined essential health service lists 1. Country name abbreviations: RWA (Rwanda), ETH (Ethiopia), SLE (Sierra Leone), LBR (Liberia), MDG (Madagascar), MOZ (Mozambique), AFG (Afghanistan), MWI (Malawi), SOM (Somalia), ERI (Eritrea), GMB (Gambia) their expenditures from domestic government sources (Fig. 5).When considering time trends, only five countries-Afghanistan, Burkina Faso, Gambia, Niger, and South Sudan-exhibited an upward trend in government expenditures from 2016 to 2020, while Sierra Leone, Sudan, and Uganda reduced their government funds during the same period.Out of the eight countries that received external funds, four experienced a decline in annual receipts.These countries are Afghanistan, Guinea, Sierra Leone, and South Sudan.Interestingly, these reductions did not lead to significant decreases in the overall expenditures on dental outpatient care in Afghanistan and South Sudan, attributed to the increased financial support from their respective domestic governments (Web Appendix 10).Furthermore, we observed significant discrepancies in the recorded per capita expenditures on dental outpatient care in 2019 between the two data sources.These disparities are particularly notable for countries such

Number of oral health professionals
Our literature review identified three papers highlighting a significant shortage of oral health professionals in low-income countries [99][100][101].For the WHO National Health Workforce Account [33], from 2010 to 2021, twenty-six low-income countries reported workforce data on dentists, while only twelve countries reported data on dental prosthetic technicians, and sixteen countries reported data on dental assistants and dental therapists.Somalia is the only country that did not report any oral health workforce data.
On average, the most recent dentist density is remarkably low, standing at 0.51 per 10,000 population across low-income countries (Fig. 6).This number is less than one-fifth of the density in middle-income countries (2.83) and represents a mere one-fifteenth of the density in high-income countries (7.62) [33].By individual country, only five low-income countries exceeded the average line of 0.51.These countries are the Syrian Arab Republic (6.61), North Korea (2.19), Sudan (2.13), Afghanistan (0.71), and Eritrea (0.54).The remaining countries exhibited considerably low dentist densities, ranging from 0.01 to 0.21 dentists per 10,000 population.
We also observed that some countries relied on other types of professionals, encompassing dental prosthetic technicians, dental assistants, and dental therapists, rather than predominantly on dentists to deliver oral health care services.For example, Sierra Leone's workforce is primarily composed of dental prosthetic technicians.In countries such as Uganda, Malawi, Guinea-Bissau, Gambia, Burkina Faso, Mali, Togo, and Liberia, there is a higher prevalence of dental assistants and dental therapists compared to dentists (Fig. 7).However, the average density of other dental professionals in low-income countries remained remarkably low, with only 0.07 dental prosthetic technicians and 0.08 dental assistants and dental therapists per 10,000 population, compared to 0.46 and 0.83 in middle-income countries and 2.11 and 5.88 in high-income countries.We grouped findings of the five study aspects by country in Web Appendix 12.For oral health expenditures, we summarized countries' most recent data on per capita expenditures on oral outpatient care in Web Appendix 12.

Discussion
Given the rising prevalence of oral diseases worldwide and the recent international commitment to achieving universal coverage for oral health by 2030, our study offers timely information on the universal coverage states for oral health in 27 low-income countries.Overall, we identified that there are limited sources of information on oral health in low-income countries, highlighting an urgent need to intensify efforts in progress monitoring and strengthening oral health care systems.
The extent of integrating oral health in national health policies varies across the 27 low-income countries.Notably, only nine countries have developed national oral health policies; thirteen countries lack such specific policies but have significantly incorporated oral health within their other national health policies.However, as a particular concern, five countries lack both national oral health policies and an adequate mention of oral health within their other national health policies, indicating neglect of political commitment to oral health in these nations.Furthermore, our study revealed that only five low-income countries (Afghanistan, Burkina Faso, Eritrea, Gambia, and Madagascar) have explicitly included oral health in national health policies designed for maternal, children, and elderly health [35,42,62,71,75].This small number reflects that the concept of treating oral disease as a progressive condition throughout the life course received little attention from policy makers in low-income countries.
In addition, we identified a large deficiency in oral health service provision in low-income countries.According to WHO, the African region faces a substantial disease burden from seven oral diseases, including dental caries, periodontal diseases, oral cancers, noma, oral manifestation of HIV and AIDS, orofacial trauma, and cleft lip and palate [23].Accordingly, the WHO recommended the inclusion of three key interventions-oral urgent treatment, affordable fluoride toothpaste, and atraumatic restorative treatment-in the basic package of oral care for resource-limited settings [90].However, we found that only four low-income countries explicitly included some of these three key interventions in their government-defined essential health care service lists, and no low-income countries listed noma and the management of the oral manifestation of HIV and AIDS.In contrast, we observed a skewed prioritization toward invasive clinic procedures, such as tooth extraction and dental abscess drainage, rather than preventive interventions delivered in a public health approach, for example, the usage of affordable fluoride toothpaste.This finding reconfirmed the deep-seated Westernized model of dentistry in low-income countries, which relied on a clinical interventionist philosophy but oversight addressing oral health issues in an upstream and community-based approach [1].
An example of an upstream public health approach that we identified is the integration of fluoride usage and school interventions in Mozambique.In its Health Sector Strategic Plan 2014-2019 [45], Mozambique prioritized access to fluorides through the widespread use of fluoride toothpaste, water fluoridation, and fluoridebased mouthwash for children aged 6-12.Additionally, in its National Oral Health Strategy 2019-2024 [46], the country advanced oral health education and daily interventions such as tooth brushing in schools.These public health strategies hold the potential to enhance the accessibility and affordability of effective upstream interventions, empower individuals with self-care skills for oral hygiene, and cultivate health behaviors that favor oral health [15].We advocate for low-income countries to share experiences on advancing oral health prevention, promotion, and management services, and to implement the WHO Global Oral Health Action Plan 2023-2030 according to their national priorities and context.This approach mirrors the efforts of South-East Asian countries, as highlighted in the Report for the Regional Meeting for Implementing the Action Plan for Oral Health 2022-2023, where countries emphasized interactions and experience sharing on oral health systems across the region [102].
In addition, our study indicates that data on oral health care utilization, oral health care expenditure, and workforce are very limited in low-income countries, reflecting countries' low level of investment in progress monitoring and system strengthening for oral health.For example, we only observed three countries (Afghanistan, Burundi, and Rwanda) that included the development of oral health professionals in their national health human resource plans [56,61,64].Furthermore, despite the evidence that out-of-pocket expenditures for oral health care are among the main drivers of catastrophic health expenditures [10,11], most low-income countries with available expenditure data still require a dominant proportion of payments to be borne by the domestic private sector.Considering that most low-income countries simultaneously lack a provision for WHO-recommended interventions, our study unveiled a worrisome situation of spending valuable out-of-pocket resources on the less-effective and sometimes harmful measures, like the removal of the uvula and dental buds for children [103].Relying on traditional oral health interventions has been demonstrated as not financially sustainable in lowincome countries [104], and we call for policy makers to reconfigure the oral health system and better reorientate public and private financial resources toward recommended evidence-based interventions.Furthermore, the discrepancies in expenditure data between international data sources underscore the need for increased efforts within the international community to coordinate endeavors in data collection.Such coordination is essential in providing policy makers with aligned and reliable measurement results, thereby supporting evidence-based policymaking when allocating financial resources to oral health.
Our study has several limitations.First, when searching for national policies containing oral health information, we used the websites of countries' health departments and WHO's existing databases.This approach may overlook oral health information contained in policies released by other departments, such as the education departments.Second, we employed public-facing websites and databases to download national health policy documents.This approach does not eliminate the possibility that oral health policies might be outlined in government internal documents that are not publicly accessible.Additionally, there remains the chance that updated versions of the accessible documents exist, but their existence is unknown to us.For future analyses, we recommend using personal contact to identify dedicated government staff responsible for oral health to locate relevant policy documents.

Conclusions
Our study provides a comprehensive examination of five aspects of universal health coverage for oral health care in low-income countries.Policy integration for oral health care significantly varied across the 27 low-income countries while most countries do not have dedicated national oral health policies and lack services that tackle oral health within the framework of common risk factors with non-communicable diseases.Tooth extraction and other invasive interventions are dominant in lowincome countries, with only a few countries adhering to WHO recommendations on the provision of preventive and public health measures for oral health, which is concerning.Financial and human resources are scarce in low-income countries, and more political and resource commitment is needed to reverse the low utilization rates in low-income countries.

Figure 2
Figure 2 illustrates the distribution of the 96 included articles across countries.Notably, Rwanda stands out with the highest number of included articles at ten, followed closely by Afghanistan and Ethiopia at six.The remaining countries generally have articles ranging from one to five.We included one peer-reviewed article and one grey literature (the WHO Global Oral Health Status Report) that examined oral health resources in multiple low-income countries.For the twelve peer-reviewed papers, Table3demonstrates that nine out of them are questionnaire-and screening-based research that provided information on oral health care utilization, while three discussed the current stock or the development of oral health professionals.Out of the 84 pieces of grey literature, 28 consist of the WHO Global Oral Health Status Report and its associated country profiles, while the remaining 56 comprise the most recent national health policies with oral health care information.Figure3illustrates that the 56 national

Fig. 2
Fig. 2 Distribution of the 96 included articles across countries

Fig. 3
Fig. 3 Distribution of the 56 included policy documents over policy types.*RMNCH: Reproductive, Maternal, Newborn and Child Health

Fig. 4 Fig. 5
Fig. 4 Per capita expenditures on dental outpatient care in 2019 based on Global Oral Health Status Report.Note: Currency in US dollar

Fig. 6
Fig. 6 Most recent number of dentists per 10,000 population in 27 low-income countries.(Data source: WHO National Health Workforce Accounts Data Portal)

Fig. 7
Fig. 7 Most recent number of dentists, dental prosthetic technicians, and dental assistants and therapists per 10,000 population in 27 low-income countries.(Data source: WHO National Health Workforce Accounts Data Portal)

Table
27 low-income countries included in this studyAfghanistan, Burkina Faso, Burundi, Central African Republic, Chad, Democratic Republic of the Congo (Congo DR), Eritrea, Ethiopia, Gambia, Guinea, Guinea-Bissau, Liberia, Madagascar, Malawi, Mali, Mozambique, Niger, North Korea, Rwanda, Sierra Leone, Somalia, South Sudan, Sudan, Syrian Arab Republic, Togo, Uganda, Yemen Index Medicus, and Dentistry and Oral Sciences Source.Two librarian coauthors (JC and MB) developed keyword search strings and adapted them for different databases.Table2shows the search string for PubMed.Search strings for other bibliographic databases are presented in Web Appendix 1.As shown in Table

Table 2
Search strings for PubMed

Table 3
Summary of the 12 included peer-reviewed studies