Determinants of dental caries in children in the Middle East and North Africa region: a systematic review based on literature published from 2000 to 2019

Background Dental caries risk factors have been expanded to not only emphasize biology, dietary and oral habits but also broader social determinants such as socioeconomic factors and the utilization of health services. The aim was to review sociobehavioural/cultural and socioeconomic determinants of dental caries in children residing in the Middle East and North Africa (MENA) region. Methods A search was conducted in the PubMed/Medline database and Google Scholar to identify studies published from 2000 to 2019 covering children using key search terms. In the initial stages, titles, abstracts and, if needed, full articles were screened for eligibility. In the final stage, all included articles were reassessed and read, and relevant data were extracted. Results Out of 600 initial articles, a total of 77 were included in this review, of which 74 were cross-sectional, 2 were longitudinal and one was a case–control study. The studies included a total of 94,491 participants in 14 countries across the MENA region. A majority used the World Health Organization scoring system to assess dental caries. The caries prevalence ranged between 17.2% and 88.8%, early childhood caries between 3% and 57% and decayed missing filled teeth (dmft) varied between 0.6 and 8.5 across the various age groups. Increased age, low maternal education, low overall socioeconomic status, decreased frequency of tooth brushing, low parental involvement, poor oral habits, infant feeding practices and sugar consumption were among the most prevalent determinants for increased risk of caries in the reviewed studies. Conclusions Dental caries was found to be high among children in many of the studies published from MENA. The key determinants of dental caries were found to include factors related to child characteristics, family background, oral hygiene and infant feeding and eating habits. The high dental caries prevalence emphasises the need to address the prevailing modifiable sociobehavioural and socioeconomic determinants by translating them into effective oral health prevention policies and programmes.

basic prevention measures [1]. Since the declaration of the Millennium Development Goals (MDGs) in 2000 and later the Sustainable Development Goals (SDGs), both of which allowed for tracking countries' health profiles, the profile of the Middle East and North Africa (MENA) region has undergone notable changes [2]. In some MENA countries, political stability, economic growth and investments in healthcare systems have led to improvements in various health indicators, whereas some countries have been impacted by political unrest or war; subsequently, the region currently includes lowmiddle income, upper-middle income and high income countries [3,4]. These societal changes have also contributed to an increased rate of non-communicable diseases and persistence of some communicable diseases, such as dental caries, due to a marked shift in lifestyle, increased food availability and a notable nutritional transition among citizens [4].
Globally, the profile of dental caries is also heterogeneous across developing and developed countries, with large disparities reported between and within groups [5,6]. Principally, it has been claimed that dental caries is decreasing in most industrialized countries due to improvements in prevention programmes and increased access to dental health services, but conflicting results have shown that dental caries is still prevalent among underprivileged groups in many of these countries [5,7,8]. In most developing countries, dental caries levels were low until recent years, after which an increase has been observed due to growing consumption of sugars, inadequate exposure to fluorides and limited access to oral healthcare services [5,8,9]. In the MENA region, trends in dental caries have shown a rapid increase in the incidence of the disease, with most caries remaining untreated [10]. Existing data from the Eastern Mediterranean Region (EMRO) from 20 countries show wide variations in dental caries with decayed, missing, and filled teeth scores (DMFT) among 12-year-olds ranging from 0.4 to 4.4 and a higher prevalence and severity of dental caries in the primary dentition than in the permanent dentition among 6-year-olds [10]. Furthermore, distinctions between dental caries experiences are present, with high rates of untreated caries in developing countries, which reflects the limited resources available and difficulties in accessibility and affordability to essential oral health care services [10,11].
While determinants that contribute to the initiation and progression of dental caries are complex and multifactorial, understanding their role is crucial for establishing appropriate prevention and management strategies [12]. The determinants can be divided into biological, contextual/environmental, sociobehavioural/cultural and socioeconomic factors [13,14]. Examples of biological determinants include host susceptibility and oral flora, and the contextual/environmental determinants include access to and utilization of dental healthcare services, oral health promotion programmes and fluoridation of water [15]. Moreover, examples of sociobehavioural/cultural determinants regarding dental caries include dental hygiene practices, consumption of sugars, lifestyle habits such as alcohol consumption and tobacco use [16]. To the best of our knowledge, there are no recent studies focusing on sociobehavioural/cultural and socioeconomic determinants of dental caries in children residing in the MENA region. Hence, the aim of the review was to address this gap in the literature.
The central questions for this review, which incorporated literature from 2000 to 2019 published from the MENA region were:

What sociobehavioural and socioeconomic variables
have been studied within the context of dental caries prevalence in children, aged 0-20 years? 2. What did the reviewed studies reveal about the influence of sociobehavioural and socioeconomic variables on the risk for dental caries in children? 3. What recommendations can be made for future research?

Methods
Electronic searches of databases (PubMed and Medline) supplemented by the use of an online search engine (Google Scholar) were used to explore determinants and prevalence of early childhood caries (ECC) or dental caries in children and young adults (age 0-20 years) residing in the MENA region. The World Atlas categorization of the MENA region was used, and accordingly, the following countries were included: Algeria, Bahrain, Egypt, Iran, Iraq, Jordan, Kuwait, Lebanon, Libya, Morocco, Oman, Palestine, Qatar, Saudi Arabia, Syria, Tunisia, Turkey, UAE and Yemen. Combinations of the following MeSH terms were used to identify relevant articles: "caries", "children", "determinants", "behaviours", "dietary causes", "dietary habits", "education, factors, income, socio, social determinants and geographic context (each of the individual countries, e.g., Egypt, Middle East and North Africa

Screening process
A comprehensive literature search was performed and updated until June 2020. One author (AM) undertook the literature search in the specified search databases after which the two other authors (AE and MG) removed all the duplicates, identifying 600 articles. The titles and abstracts of the 600 articles were read by all authors and screened for relevance. AE and MG applied the inclusion and exclusion criteria, and when in doubt about the eligibility of an article, both independently read the abstract and, if necessary, the full-text article, after which it was discussed and full consensus was reached. Duplicate references were checked and removed using Endnote bibliographic software [17].

Inclusion and exclusion criteria
From the identified 600 articles the inclusion and exclusion criteria were applied. The initial screening process was conducted to include only articles in English published during January 2000-January 2019 within the MENA region. Following this, the titles, abstracts and, when needed, the articles' full text were screened according to their relevance to the scope of this study, the study design, health and medical conditions in the studied population and finally the age group. Articles that were not relevant to sociocultural, sociobehavioural and socioeconomic determinants of dental caries, such as those examining microbiological and genetic predictors of dental caries, were outside the scope of this study and were therefore excluded. Original cross-sectional studies, case-control studies and longitudinal studies were included, whereas reviews, interventional studies, case reports and editorial commentaries were excluded. Furthermore, studies focusing on children/young adults with certain health and medical conditions (cardiovascular disease, autism, diabetes, Down syndrome, etc.) were excluded. The final inclusion criterion that was applied was age; articles reporting results from children, teenagers and young adults aged 0-20 years were included, whereas findings related to adults were excluded. A few relevant articles where the full-text articles were not accessible were also excluded. This resulted in 77 articles being included for this study, and 523 articles were excluded as described in Fig. 1.

Determinants related to child characteristics
The author calculated this as follows the decayed or filled teeth (%)      Association: Positive ( +), negative (−) refers to this factor being either a statistically significant risk factor for caries (positive, +) or to this factor being statistically significant protective against caries (negative, −). In some studies it could not be determined whether a factor was positively or negatively associated with caries and in these cases the relation is described as unclear b The CAST index scoring system is as follows: "0: sound", "1: sealant", "2: restoration", "3: enamel lesions", "4, 5: dentine lesions", "6: pulp involvement", "7: abscess/fistula", "8: tooth loss". If a situation did not match any codes from 0 to 8, a code 9 was assigned. The codes 0-2, 3, 4-5, 6-7, and 8 were considered as "healthy", "pre-morbidity", "morbidity", "serious morbidity", and "mortality", respectively         Association: Positive ( +), negative (−) refers to this factor being either a statistically significant risk factor for caries (positive, +) or to this factor being statistically significant protective against caries (negative, −). In some studies it could not be determined whether a factor was positively or negatively associated with caries and in these cases the relation is described as unclear b The authors describe their scoring as WHO(DMFT) whereas it should be noted that the age group is 3-6 year olds where normally WHO (dmft) is being used c Based on the baseline assessment the participants were categorized into; Group I having sufficient oral health behaviours, Group II having moderate oral health behaviours and Group III having insufficient oral health behaviours and then the participants were followed for a 2-year period The CAST index scoring system is as follows: "0: sound", "1: sealant", "2: restoration", "3: enamel lesions", "4, 5: dentine lesions", "6: pulp involvement", "7: abscess/fistula", "8: tooth loss". If a situation did not match any codes from 0 to 8, a code 9 was assigned. The codes 0-2, 3, 4-5, 6-7, and 8 were considered as "healthy", "pre-morbidity", "morbidity", "serious morbidity", and "mortality", respectively        The feeding type had an impact on the caries prevalence as follows: 75.39% of breastfeed children, 70.39% of the formula fed, 68.67% of those who were weaned and 55% of those who got a mix of breast milk and formula had dental caries respectively l During the baseline sampling mothers reported that they put their child's spoon into their own mouth while feeding their child Table 3 describes the statistically significant determinants related to family background, such as socioeconomic, sociodemographic, geographical location, school type (private or public), and parents' education level, as potential risk factors contributing to dental caries. A total of 20 studies found negative associations with maternal education (13 studies) [21,26,29,31,37,52,57,58,60,67,81,83,89], paternal education (3 studies) [24,27,50], or education of both parents combined (4 studies) [20,38,40,42] (Table 3). Parents' employment status was found to be either positively or negatively associated with caries in seven studies [21,22,32,37,38,62,80]. Although there was no coherent measurement of socioeconomic status between the reviewed studies, overall socioeconomic status (SES), income, affluence or access to dental insurance were found to have a negative association with dental caries in seven studies, whereas Bener et al. found a positive association between household income and dental caries in Qatar [55]. In addition, significant associations were found between family size, order and numbers of siblings, rural or urban residency, nationality and school type in various studies (Table 3).

Determinants related to oral hygiene
In the reviewed studies, oral hygiene and oral practices were assessed directly using plaque or oral hygiene indices or indirectly using self-reports by parents/guardians or participants. Table 4 illustrates statistically significant oral hygiene-related determinants contributing to dental caries. In 11 studies, an association between the frequency of tooth brushing and dental experience was found with reduced dental caries prevalence among those who frequently brushed their teeth and vice versa [20,22,37,40,55,60,66,81,84,89,91]. Some studies reported an association between parental-related factors such as supervision of tooth brushing (mainly in primary dentition), parental knowledge about oral hygiene, or parental caries status and the caries experience in their children (Table 4). Table 5 presents the statistically significant determinants/ risk factors related to infant feeding and eating habits contributing to dental caries. Infant feeding practices such as breastfeeding, bottle feeding and mixed feeding were all positively associated with dental caries in different studies. Furthermore, four studies found a positive association between night feeding and caries [18,19,34,83]. Other factors, such as bottle feeding on demand, sleeping with the bottle, sleeping next to the mother, using a (sweetened) dummy, or sharing a spoon with the mother, were also positively associated with caries ( Table 5).

Discussion
The purpose of this review study was to identify, gather, assess and summarize evidence from scientific studies to address sociobehavioural/cultural and socioeconomic determinants of dental caries among children residing in the MENA region. A structured approach was used to identify 77 relevant studies from 14 countries (Egypt, Iran, Iraq, Jordan, Kuwait, Lebanon, Libya, Palestine, Qatar, Saudi Arabia, Syria, Turkey, UAE, and Yemen), whereas no relevant studies were found from Algeria, Bahrain, Morocco, Oman and Tunisia, highlighting a knowledge gap about children's dental status in these specific countries. This study showed a high caries prevalence in many studies regardless of age group or publication date, indicating a worsening dental health status in the MENA region compared to previous reports [95]. The most commonly reported socioeconomic/demographic and behavioural determinants of dental caries in children reported in this review included low parental education level, low household income, frequent consumption of sugars and/or poor dietary habits and poor oral habits, including tooth brushing, dental visits and parental engagement or knowledge on oral hygiene.

Age and gender as determinants for dental caries
Increased age was identified as an independent risk factor for dental caries in several studies, probably reflecting the cumulative effect of the disease, which is on par with the literature [14,98]. Although females may be expected to exhibit a higher caries rate due to earlier tooth eruption, and thus longer exposure to cariogenic processes, variations in the associations between sex and dental caries were found in this study. Female sex was associated with a higher risk in six studies, whereas males were at a higher risk in eight of the studies. Others have attributed sex variations to differences in dietary and oral hygiene behaviours or utilization of oral health care [99,100].

Sociodemographic determinants for dental caries
The role of parental variables that are directly associated with children's oral health, including sociodemographic characteristics, oral health behaviours, access to health services and other attributes, is evident in this study. In a recent study, this was validated through a conceptual model [101]. SES is generally measured by indicators of human capital, such as income, education, urban/rural living, and occupational nature, which offer advantages or disadvantages to individuals and families. In line with findings from other regions and despite the differences in measuring SES in the reviewed articles, socioeconomic factors were shown to have a significant impact on dental caries [14]. It was primarily mothers' level of education, but also other factors, such as parental occupation, unemployment, low-skilled occupation, low income, overall SES and school type, that were identified as determinants of caries (Table 2).

Dietary determinants for dental caries
Most dietary determinants for caries were related to sugar intake: consumption, amount, frequency or timing of sweet beverages, snacks and/or food. The current findings in establishing sugar intake and SES factors as key determinants of dental caries in the region are consistent with those of studies in several other countries that have demonstrated socioeconomic gradients in sugar consumption and may accordingly prompt dietary recommendations in limiting added sugar intake and targeting SES disadvantaged groups in the region [102][103][104]. Moreover, other determinants were identified, such as a lack of an overall healthy diet or intake of certain nutritious foods, which again emphasizes the importance of promoting healthy eating habits and the need for dietary guidelines.
Regarding infant feeding practices, the findings in this study were inconclusive, indicating that both bottle feeding and breastfeeding were associated with higher caries prevalence in different studies [21,44,55,60]. These findings are in contrast with those in a systematic review and meta-analysis that concluded that breastfeeding seems to be protective against dental caries when compared to bottle feeding [105].

Oral hygiene determinants for dental caries
Tooth brushing as a determinant for caries was a distinct finding in this study; a reduced dental caries experience could be found among those who frequently brush their teeth and vice versa, and this was more apparent in the young age groups with primary dentition [20,22,37,40,55,60,66,81,89,91]. Additional determinants related to tooth brushing included age of brushing initiation, frequency, adult supervision and the presence of visible plaque. These factors are all interrelated factors that could potentially also be linked to SES [106,107].

Methodological considerations
In this review, the associations between determinants and dental caries were mainly projected from crosssectional studies. These methodological choices, i.e., the study design (cross-sectional), sampling procedures (e.g., non-population based, convenience sampling), assessment setting and/or outcome measures may be an expected consequence of the relatively immature research infrastructure, limited resources in some of the MENA countries or may be related to social or political turmoil that some countries have experienced [41,108]. Although cross-sectional studies may be a feasible option in such circumstances, they only provide a snapshot of risk factors that are associated with the outcome, but causal pathways cannot be determined since the exposure and outcome are measured simultaneously [109]. On the other hand, case-control and longitudinal studies offer greater scientific evidence through better control of possible methodological biases and data analysis, and over time, these types of studies will be needed to further develop and strengthen the research landscape [108]. The aforementioned imbalance in research output between countries hinders the establishment of a comprehensive dental caries profile of the MENA region. This imposes the need to increase dental caries research output in some countries and to devote more rigorous, unique (not repetitive), up-to-date and representative research from others. These steps can strengthen the ability to comprehensively assess trends and determinants of dental caries in the region, allow for cross-country comparisons and identify regional variations in the future.

Strengths and limitations
The strengths of this study include the systematic approach employed in assessing the articles published during a period of 20 years focusing on children and young adults. Furthermore, this study focused mainly on modifiable determinants in a region with a young population, which can guide informed dental public health actions and thereby decrease health inequities. The results in this study were reported without assessing the strength/power or the quality of either the study design, sampling procedures or the statistical analysis of the included articles, which can be seen as limitations. Furthermore, the methodological heterogeneity (study design, age group, exposure, outcome measurements, covariates, statistical analyses) among the studies included in this article may have influenced the interpretation of the results; hence, these findings need to be confirmed or rejected by future studies. However, drawing the comprehensive landscape of the disease and its determinants offers an outlook in a relatively understudied region which is a prerequisite for designing follow-up studies. Future studies may focus on appraisal and quality assessment of the reviewed studies, using tools such as those suggested by Migliavaca et al. for prevalence studies [110].

Conclusions
To conclude, the prevalence of dental caries among children and young adults in the MENA region was high. Despite heterogeneity in the study designs and assessment methods of dental caries, the main determinants of dental caries were found to include age, sex, mother's education, overall socioeconomic status, tooth brushing frequency, parents' oral habits/knowledge and sugar consumption. The high dental caries prevalence imposes the need to address the prevailing modifiable sociobehavioural and socioeconomic determinants by translating them into effective oral health prevention policies and programmes. Moreover, a special emphasis on strengthening regional oral health research would further enhance the knowledge and understanding of a major public health problem in the region.