Caries Preventive Interventions and Oral Health Inequalities: A Scoping Review

Introduction: Dental caries remains one of the most prevalent but preventable diseases among children worldwide and especially affects children with a lower socioeconomic status or ethnic minority background. It is important that all groups of children are reached by preventive interventions to reduce oral health inequalities. So far, it is unknown whether children from different social and ethnic groups benefit equally from potentially effective oral health interventions. Objectives: This scoping review aimed to identify European public health interventions that report their effect on dental caries across different social groups. Methods: Four databases were searched for studies evaluating the effect of oral health interventions on dental caries among children from 0 to 12 y, and studies were included when results were presented by children of different social groups separately. Results: A total of 14 studies were included, representing 4 different countries: 3 randomized and 11 nonrandomized studies. Most studies were performed at schools. Six studies showed results indicative of a reduction in oral health inequalities, 4 studies showed results that potentially widen oral health inequalities, and 5 studies showed results that were indicative of no impact on oral health inequalities. Interventions that contain early approaches, with a high frequency, approaching multiple levels of influence, and including at least the broader organizational or public policy level, may have the potential to reduce oral health inequalities among children from birth to young adolescence. Conclusion: We recommend researchers to perform high-quality intervention studies and to evaluate the effectiveness of oral health intervention always in different socioeconomic or ethnic groups separately, to better understand their contribution toward oral health (in)equalities. Knowledge Transfer Statement: This review offers insight in the differential effects that oral health interventions might have across different social groups. Its results can be used to develop interventions that might reduce oral health inequalities among children. Also, we recommend future researchers to always evaluate the effects of any preventive oral health measure in different social groups separately.


Review
Abstract: Introduction: Dental caries remains one of the most prevalent but preventable diseases among children worldwide and especially affects children with a lower socioeconomic status or ethnic minority background.

It is important that all groups of children are reached by preventive interventions to reduce oral health inequalities. So far, it is unknown whether children from different social and ethnic groups benefit equally from potentially effective oral health interventions.
Objectives: This scoping review aimed to identify European public health interventions that report their effect on dental caries across different social groups.
Methods: Four databases were searched for studies evaluating the effect of oral health interventions on dental caries among children from 0 to 12 y, and studies were included when results were presented by children of different social groups separately.
Results: A total of 14 studies were included, representing 4 different countries: 3 randomized and 11 nonrandomized studies.Most studies were performed at schools.Six studies showed results indicative of a reduction in oral health inequalities, 4 studies showed results that potentially widen oral health inequalities, and 5 studies showed results that were indicative of no impact on oral health inequalities.Interventions that contain early approaches, with a high frequency, approaching multiple levels of influence, and including at least the broader organizational or public policy level, may have the potential to reduce oral health inequalities among children from birth to young adolescence.

Introduction
Dental caries is one of the most prevalent, but neglected, noncommunicable diseases among children worldwide (The Lancet 2009; Kassebaum et al. 2015).Dental caries is preventable, and it is known that preventive care has positive longterm consequences in terms of wellbeing and cost-effectiveness (Selwitz et al. 2007;The Lancet 2009;Pitts et al. 2017).Therefore, especially intervening at a young age is important to maintain proper oral health behaviors during adulthood (Halfon and Hochstein 2002).Dental caries among children has been reduced in European countries in the previous decade, but still a stagnation or even worsening in its prevalence prevails (Watt and Sheiham 1999;Pitts et al. 2017;Schuller et al. 2018).Especially socially disadvantaged children, indicated by low socioeconomic status or ethnic minority background, are more often affected by poor oral health, including dental caries (Watt and Sheiham 1999;Schuller et al. 2018).Therefore, in a recent report from the World Health Organization (WHO), for setting goals for 2030, concerns are raised about the existing oral health inequalities that were not reduced in the past years and due to the COVID-19 pandemic might be even further increased (WHO 2021).
Several oral health interventions that could prevent dental caries among children do exist on an international basis, and previous researchers have summarized and evaluated those for their effectiveness (dos Santos et al. 2013;de Silva et al. 2016).Also, 1 systematic review has been performed on dental preventive strategies among disadvantaged children solely (Skeie and Klock 2018), and 1 recent review summarized the effect of intervention studies on oral health inequalities based on the analyses, reporting, and interpretation of the individual studies (Shen et al. 2021).However, so far, the effects of oral health interventions have not been objectively summarized and evaluated for different groups of social status separately.This is alarming since from research beyond the field of oral health, it is known that effective interventions can increase health inequalities as children belonging to affluent social groups (e.g., high socioeconomic status or ethnic majority background) are reached better and benefit more from preventive interventions than disadvantaged groups (e.g., low socioeconomic status or ethnic minority background) (Lorenc et al. 2013).So far, no study has been performed to gain more insight into potential reasons for the differential impact of interventions on oral health in a systematic manner.Insight in characteristics of interventions that could reduce or induce oral health inequalities could help future researchers and policy makers in the development of oral health intervention programs.Moreover, previous reviews include intervention studies that were carried out in the United States, Australia, Brazil, or lowincome countries.Even though the oral health of inhabitants among European countries is relatively good compared to other continents, at the same time, oral health inequalities exist in all European countries (Forster et al. 2018).Especially, because most European countries pay limited attention to oral health inequalities within their policy, the need for research in oral health promotion to develop comprehensive strategies is urgent (Patel 2012).Given the limited insight in the prevention and reduction of oral health inequalities, a scoping review was performed.Scoping reviews are a type of review that is commonly used to explore and summarize evidence of all available literature, to identify knowledge gaps, and to inform future research, especially when gaining insight in intervention programs (Peters et al. 2020).Therefore, the aim of this scoping review was to identify European public health interventions that report their effect on dental caries in children across different social groups, to summarize the effect of these interventions across different social groups in a narrative manner, to determine the potential direction on oral health inequalities of each intervention study, and to identify common attributes of interventions according to their potential direction on oral health inequalities.

Protocol and Registration
Scoping reviews are used to identify and provide an overview of the available evidence.The main consideration to perform a scoping review is when it is not aimed to produce a synthesized answer to the research question (Munn et al. 2018).Therefore, to answer the aims of this review, a scoping review was conducted.The review reports according to the PRISMA extension for conducting Scoping Reviews (PRISMA-ScR) (Tricco et al. 2018).The review protocol was published on PROSPERO (CRD42020156635).For the selection of gray literature and unpublished results, to limit the risk of reporting bias, we performed an electronic search in WorldCat, Scientific Electronic Library Online (scielo.org),opengrey.eu,Open Access Theses and Dissertations (oatd.org),and Google Scholar, based on the following keywords: intervention, oral health, caries prevention, public health, and socially disadvantaged children.

Study Selection
Titles and abstracts were independently screened by 2 researchers (AM-L and YY) using EndNote to make the initial selection.All potentially relevant studies were read full-text by 2 researchers (AM-L and YY).In case of discrepancy, a third reviewer (LK) was consulted.Thereafter, reference lists of systematic reviews identified in the literature search and of all included studies were screened for additional relevant studies.

Data Extraction
From the final set of relevant studies, the following data were extracted: study characteristics (first author, publication year, country, study design, study population size, age, duration, setting), type of intervention, control group, outcome(s), outcome assessment, the measures of social disadvantage (e.g., indicator of SES, ethnic background, or of area deprivation score), and effect size measures used.

Analysis
The effect on dental caries of each intervention was evaluated for the lowest and highest group of social disadvantage and assessed by mean differences (MDs) or risk ratios (RRs) with corresponding confidence intervals (CIs) calculated by Student's t test or the Mantel-Haenszel procedure with a significance level of P < 0.05.To identify the potential direction of each intervention on oral health inequalities, the (significance of) effect estimates were compared.Due to the differences in study design and outcome measures and statistical heterogeneity, no statistical synthesis of results was performed, and no pooled summary measures were presented.We categorized the differential effects of each intervention per social group as follows: 1) the intervention is indicative of a potential reduction in oral health inequalities: the intervention preferentially reduced dental caries in the most disadvantaged group; 2) the intervention is indicative of a potential widening of oral health inequalities: the intervention preferentially reduced dental caries in the least disadvantaged group; and 3) the intervention is indicative of no preferential impact on oral health inequalities: the intervention equally reduced dental caries in both social groups or did not show an overall effect.Accordingly, we reported determinants of the interventions, such as type, length, frequency, setting, or the level of influence.The level of influence on health behavior was categorized as individual (knowledge, attitudes, and beliefs), interpersonal (family, friends, peers, or interactions), organizational (institutionalized rules or regulations), community (social networks and norms), and policy level (local, regional, or national policies and laws) (McLeroy et al. 1988;Rimer and Glanz 2005).

Risk of Bias
This is a scoping review, and generally all available evidence regardless of the methodological quality is included.In order to examine how previous research was conducted and which elements contribute to the quality of the evidence, we additionally present a risk of bias analysis.These results will give guidance and recommendation for future research.To assess the risk of bias in the individual studies, the Quality Assessment Tool for Quantitative Studies from the Effective Public Health Practice Project was used (Effective Public Healthcare Panacea Project 1998; Jackson and Waters 2005).This is a validated assessment method to rate the methodological quality of both randomized and nonrandomized intervention studies recommended for evaluating public health programs (Jackson and Waters 2005;Armijo-Olivo et al. 2012).The tool includes 6 components, including selection bias, design, confounders, blinding, data collection methods, and withdrawals and dropouts.Study components were rated as strong, moderate, or weak, and the study was rated strong if none of the components were rated weak, moderate if 1 component was rated weak, or weak if 2 or more components were rated weak.

Selection of Studies
The study selection is summarized in the Figure .Electronic searches retrieved a total of 3,639 unique references.Titles and abstracts were screened, and 174 studies were selected for fulltext screening.Finally, a selection of 14 articles was included in the present study.The main reasons for exclusion were non-European countries, no stratification into social groups, no evaluation of an intervention program, or studies without a control group.

Quality of Included Studies
In Table 1, the global rating of the methodological quality of the included studies is presented, and an extended table including the rating of all 6 components is presented in Appendix Table 1.Of the included studies, 3 were rated as strong (Winter et al. 1989;Qadri et al. 2018;Kidd et al. 2020), 5 were rated as moderate (Evans et al. 1996;Freeman et al. 2001;Levin et al. 2009;Wagner and Heinrich-Weltzien 2017;Winter et al. 2018), and 6 were rated as weak in terms of study quality (Dargent-Paré et al. 1999;Ellwood et al. 2004;Heinrich-Weltzien et al. 2007;Drosen et al. 2010;McMahon et al. 2011;MacPherson et al. 2013).

Effect of Interventions across Social Groups
Interventions that may reduce inequalities Six studies showed results that were indicative of a reduction in dental health inequalities (Evans et al. 1996;McMahon et al. 2011;MacPherson et al. 2013;Wagner and Heinrich-Weltzien 2017;Winter et al. 2018;Kidd et al. 2020) (Table 2 and Appendix Table 2).The first study showed that children living in the fluoridated areas had statistically significantly lower caries levels than children in the nonfluoridated areas.Moreover, children in the low social class showed a higher reduction in dental caries (Evans et al. 1996).The second study showed that children from the most deprived areas had a significantly  To assess the risk of bias in the individual studies, the quality assessment tool for quantitative studies from the effective public health practice project was used.2).Bold font effect estimates indicate statistical significance (P < 0.05).CI, confidence interval; dmft, decayed missing filled teeth in primary dentition; DMFT, decayed missing and filled teeth in permanent dentition; dmfs, decayed missing and filled surfaces in primary dentition; DMFS, decayed missing and filled surfaces in permanent dentition; d3mft, modification of dmft that assesses caries only if the decay affects the dentin layer; D3MFT, modification of DMFT that assesses caries only if the decay affects the dentin layer; d1-4mfs, modification of dmfs that assesses caries reaching both enamel and dentin; d3-4mfs, modification of dmfs that assesses caries only if the decay affects the outer and inner dentin layers; MD, mean difference; RR, risk ratio; SES, socioeconomic status; ∆, increment.a The potential impact on oral health inequalities is reported using symbols indicating the following: ↓ if the intervention is likely to reduce inequalities; ↑ if the intervention is likely to widen inequalities; and ↔ if the intervention had no differential impact on the 2 groups.
b The groups refer to different intervention elements as indicated in Table 1.The sixth study showed that children in intervention group 2 (receiving supervised toothbrushing, toothbrushing exercise, free toothbrush and toothpaste at kindergarten, and instructions on toothbrushing at primary school) and with low SES had statistically significantly lower dental caries compared to the control group, which received basic dental education at primary school only.Among children of high SES, this decrease in dental caries was not observed (Winter et al. 2018).

Interventions that may widen inequalities
Four studies showed results that were indicative of a widening in oral health inequalities (Dargent-Paré et al. 1999;Heinrich-Weltzien et al. 2007;Levin et al. 2009;Qadri et al. 2018) (Table 2 and  Appendix Table 2).One study showed that children from both employed and unemployed fathers who received an intervention program, including several elements (including provision and promotion of several fluoride measures), showed significantly reduced dental caries, where the difference among children from employed fathers was largest (Dargent-Paré et al. 1999).Another study evaluated the effect of an extended preventive program where the intervention group received additional preventive measures (i.e., brushing exercises, dental screening, fluoride varnish) on top of the basic program (yearly lessons and education on oral health) at primary schools.Children with an ethnic majority background showed a significant reduction in dental caries, where the group of Grammar students showed the greatest absolute difference (Heinrich-Weltzien et al. 2007).The third study evaluated the effect of biweekly supervised mouth rinsing at school with a fluoride solution, compared to children receiving no intervention.Only children from the least deprived areas showed a statistically significant decrease in dental caries (Levin et al. 2009).The last study evaluated the effect of oral health education provided by schoolteachers at primary schools, and the authors of this study calculated the incidence rate ratio in both socioeconomic groups.The educational program showed a significant protective effect on the development of dental caries in children with high SES but not with low SES (Qadri et al. 2018).

Interventions that may have no impact on inequalities
Five studies showed results that did not have a differential impact on oral health inequalities (Winter et al. 1989;Freeman et al. 2001;Ellwood et al. 2004;Drosen et al. 2010;Winter et al. 2018) (Table 2 and Appendix Table 2).One study evaluated the effect of an extended preventive program, including the basic program and additional brushing exercises, fluoride varnish, and educational games, compared to a basic program that included the yearly instruction on caries prevention and supervised toothbrushing and dental flossing.Children from both ethnic majority and ethnic minority groups did not show a statistically significant difference in dental caries, although a small reduction in dental caries was observed among children with an ethnic minority background (Drosen et al. 2010).The second study evaluated the effect on dental caries in 2 intervention groups that were provided with dental health literature, toothbrush, and free toothpaste containing either 440 or 1,450 ppm fluoride.Of the intervention group that received 1,450 ppm fluoride toothpaste, children from the nondeprived and deprived areas showed a similar absolute reduction in dental caries.Children from the intervention group receiving 440 ppm fluoride and belonging to the most deprived areas showed a nonsignificant reduction in dental caries, whereas children from the nondeprived areas showed a nonsignificant increase in dental caries (Ellwood et al. 2004).Another study evaluated the effect of a break policy at primary schools where only the consumption of milk and fruit was allowed.In both socioeconomic groups, the intervention did not significantly change the risk of dental caries (Freeman et al. 2001).The fourth study studied the effect of the provision of free toothpaste with a high fluoride content (1,055 ppm) compared to free toothpaste with low fluoride content (550 ppm).Children with both manual and nonmanual occupational class parents did not show a significant difference in dental caries (Winter et al. 1989).The last study evaluated the effect of 5 different interventions, including several components at kindergarten and primary schools (ranging from intensive to less intensive program elements), compared to children who did receive basic dental education at primary school.Although children from low SES receiving interventions 3 and 4 (receiving few times toothbrushing exercises or instructions on toothbrushing) showed an increase in caries, no statistically significant differences in effect on dental caries were observed between interventions 1, 3, 4, and 5 (Winter et al. 2018).

Common Characteristics of Interventions
Of the 6 studies that were indicative of a potential reduction in oral health inequalities (Evans et al. 1996;McMahon et al. 2011;MacPherson et al. 2013;Wagner and Heinrich-Weltzien 2017;Winter et al. 2018;Kidd et al. 2020), 3 evaluated (a part) of the "Childsmile" intervention (McMahon et al. 2011;MacPherson et al. 2013;Kidd et al. 2020).Five interventions included a daily exposure to fluoride via water or toothbrushing (Evans et al. 1996;McMahon et al. 2011;MacPherson et al. 2013;Winter et al. 2018;Kidd et al. 2020), 3 were performed from birth onward (Evans et al. 1996;McMahon et al. 2011;Wagner and Heinrich-Weltzien 2017), duration varied from 2 to 6 y, and the setting differed per study.All studies evaluated dental caries in the deciduous dentition and 1 additionally in permanent teeth (Winter et al. 2018).Furthermore, all programs incorporated the wider organizational or public policy level by implementing a setting where teeth are brushed at school regularly or having fluoridated water.
Of the 4 studies that were indicative of a potential widening in oral health inequalities (Dargent-Paré et al. 1999;Heinrich-Weltzien et al. 2007;Levin et al. 2009;Qadri et al. 2018), 3 had an infrequent exposure to the intervention program (Heinrich-Weltzien et al. 2007;Levin et al. 2009;Qadri et al. 2018), and for 1 study, frequency was unknown (Dargent-Paré et al. 1999).All studies were performed in primary schools and evaluated dental caries in the permanent dentition (Dargent-Paré et al. 1999;Heinrich-Weltzien et al. 2007;Levin et al. 2009;Qadri et al. 2018).Regarding the level of influence, 1 study focused at the individual and interpersonal level (Qadri et al. 2018) (i.e., having oral health education in class), and 3 others included a combination of the individual (i.e., provision of fluoride) or interpersonal (i.e., oral health education in class) and organizational level (i.e., implementing a fixed moment of mouth rinsing or toothbrushing in class) (Dargent-Paré et al. 1999;Heinrich-Weltzien et al. 2007;Levin et al. 2009).
Of the 5 studies that showed results that did not indicate a differential impact on oral health inequalities (Winter et al. 1989;Freeman et al. 2001;Ellwood et al. 2004;Drosen et al. 2010;Winter et al. 2018), 3 were performed at primary schools (Freeman et al. 2001;Drosen et al. 2010;Winter et al. 2018) and 2 at a home setting (Winter et al. 1989;Ellwood et al. 2004).The program frequency was mainly once or a few times a year (Winter et al. 1989;Ellwood et al. 2004;Drosen et al. 2010;Winter et al. 2018).The age when the intervention started and its duration varied.Two studies evaluated caries in mixed dentition (Drosen et al. 2010;Winter et al. 2018), 2 in deciduous dentition (Winter et al. 1989;Ellwood et al. 2004), and 1 in permanent dentition (Freeman et al. 2001).Also, the level of influence varied per study, with 2 studies solely focusing on the individual level (i.e., provision of toothpaste or toothbrush) (Winter et al. 1989;Ellwood et al. 2004), 1 merely on the organizational level (i.e., nutrition guidelines for school break) (Freeman et al. 2001), and 2 incorporated a mix of individual, interpersonal, and organizational level (i.e., oral health education, provision of fluoride or toothbrush, supervised toothbrushing in class, or fluoride varnish application) (Drosen et al. 2010;Winter et al. 2018) (Table 3).

Main Results
The present scoping review identified (components of) interventions that have the potential to reduce oral health inequalities among children.Of the included studies, 6 presented intervention strategies with a potential reduction in oral health inequalities, 4 presented intervention strategies that were indicative of a widening in oral health inequalities, and 5 presented intervention strategies that were indicative of no preferential impact on oral health inequalities.Common characteristics of interventions that may reduce oral health inequalities were a high frequency of the intervention program (daily), an early onset (from birth onward), targeting at the deciduous dentition, and incorporating at least the organizational or public policy level regarding the level of influence.

Explanation of Results
In our study, we found that the timing of the intervention, from birth onward, may play a role in the effectiveness of the intervention, especially among the most disadvantaged groups.This is supported by a previous study that concluded that targeting children at a younger age (before 24 months) could lead to greater reductions in early childhood caries (Hirsch et al. 2012).Also, another study revealed the importance of intervening during the early years of a child's life for future oral health (Chen et al. 2007).Besides, in older children with permanent dentition, disparities might be already wider due to long-term poor lifestyle behaviors that could already be present at an early age and continued throughout the years (Harris et al. 2006;Verlinden et al. 2019;Lioret et al. 2020).This theory is also supported by the WHO, which supports a good start to life for every child as a key strategy to limit the effects of social disadvantage on health during childhood and to reduce the risk of several chronic and lifestyle diseases  (Whitehead 2007;McLaren et al. 2010).
The WHO supports this by setting goals to limit health disparities, which underlines that all levels from the wider society and system should be involved when taking action to improve equal health to the whole population (Marmot et al. 2012).

Strength and Limitations
A strength of this scoping review is the comprehensive literature search in multiple databases.We aimed to include all relevant articles without language or publication year limits.Furthermore, we also included nonrandomized studies in this review.Although these individual studies may be more prone to bias, by including these studies, we were able to evaluate the effect of certain policies or regulations implemented at schools or The potential impact on inequalities is reported using symbols indicating the following: ↓ if the intervention is likely to reduce inequalities, ↑ if the intervention is likely to widen inequalities, and ↔ if the intervention had no differential impact on the 2 groups.
Table 3. (continued) communities and thereby provide a more comprehensive overview of potential measures that could be implemented to reduce oral health inequalities in the future.On the other hand, there are also limitations to consider.A limited number of relevant studies could be included in this scoping review, as we had to exclude 63 studies because of the nonstratification of social groups.Also, of the limited studies that were included, 6 were of low quality.Therefore, the results of this scoping review should be interpreted with caution.However, it clearly identifies the need for highquality studies when aiming to reduce dental caries across different social groups.If randomization is not possible, a proper description of the study population, including an overview of baseline characteristics, or taking measures to reduce loss to follow-up, could ensure that the internal validity of individual studies will not be highly affected.We only included studies from European countries, although other studies have been performed that evaluated the effect of interventions across different social groups in other continents.Nevertheless, we decided to only include European studies since these will be more homogeneous regarding fluoridated water laws, health care and school systems, and the cultural and socioeconomic backgrounds of the population.Consequently, the results of this review are applicable for and generalized to a European population setting.Another limitation is that each study determined socially disadvantaged groups differently.Also, the determination and comparison of the lowest and highest groups might differ per study.For example, when the most extreme social groups are compared (e.g., lowest 10% versus highest 10%), a much larger difference will be revealed than comparing the lowest 50% versus the highest 50% of a total population, and this might influence the conclusion regarding the potential impact on oral health inequalities per study.Moreover, in our study, we evaluate the potential impact on oral health inequalities using the (significance of) effect estimates per social group, by only including studies that reported the effect of the intervention in groups of children with different social backgrounds separately.
It should be noted that other methods exist to evaluate the impact on oral health inequalities potentially leading to a divergent conclusion (King et al. 2012).Furthermore, our scoping review mainly relies on the statistical significance of the individual study results to evaluate the differential impact of the intervention in each social group, which is highly influenced by the sample sizes of each study group (Appendix Table 2).Since most studies that were included in this review were initially not designed to study the effect of the intervention in different social groups of children separately, the sample size of each social group might be underpowered.Therefore, we cannot exclude the possibility that interventions with an effect size that clearly showed an absolute mean difference would have shown statistically significant results and a potential impact on oral health inequalities if it would have larger power.

Conclusions
The need for interventions to reduce oral health inequalities has been previously recognized.This review shows that oral health interventions may have differential effects across children from birth to 12 y from different social groups.Interventions that contain early approaches, with a high frequency, and influence multiple levels, including the broader organizational or public policy level, are most promising to reduce oral health inequalities among children.Still, the causes of inequalities in oral health remain interrelated and complex.The number of high-quality studies is very limited, which subsequently limits the conclusion of this review.In order to come up with thoroughly based conclusions, we first need more properly designed intervention studies in the field of preventive dentistry.In addition, we suggest to evaluate the effectiveness of an oral health intervention always in socioeconomic or ethnic groups separately, to better understand the effect of the intervention on oral health inequalities.

Figure .
Figure.PRISMA flow diagram for study selection.Flow diagram shows the selection of studies that were retrieved, screened, and selected for inclusion.

Table 1 .
Characteristics of Included Intervention Studies.DMFT, decayed missing and filled teeth in permanent dentition; dmfs, decayed missing and filled surfaces in primary dentition; DMFS, decayed missing and filled surfaces in permanent dentition; d3mft, modification of dmft that assesses caries only if the decay affects the dentin layer; D3MFT, modification of DMFT that assesses caries only if the decay affects the dentin layer; d1-4mfs, modification of dmfs that assesses caries reaching both enamel and dentin; d3-4mfs, modification of dmfs that assesses caries only if the decay affects the outer and inner dentin layers; NaF, sodium fluoride; RCT, randomized controlled trial; ppm, parts per million. a

Table 2 .
Effectiveness of Interventions on Dental Caries Stratified per Social Group and the Potential Impact on Oral Inequalities.

Table 3 .
Common Characteristics of Interventions Sorted by Their Potential Impact on Oral Health Inequalities.