Dental caries remains the most prevalent oral disease. The prevalence of untreated dental caries in permanent dentition was estimated at 34.1% in 2015, impacting the age-standardized disability-adjusted life year ^[1][8]. A complex net of biological, behavioral, and social factors determines the disease, and systematic reviews (SR) have shown that poverty is also an important factor to be taken into account. Lower socioeconomic positions described by educational level, income, or occupation seems to increase caries experience in different age groups ^[2][3][6,7]. An SR carried out among children in Iran ^[4][16], the Middle East, and North Africa ^[5][17] reached similar conclusions.

Severe chronic periodontitis affected 7.4% of the global population in 2015 ^[1][8]. Periodontal diseases are associated with tobacco consumption, comorbidities such as diabetes, and socioeconomic factors at both the individual and the population level. An SR approached the influence of a life-long individual-level socioeconomic position on adulthood periodontitis by evaluating seven longitudinal studies. It was found that, despite the limited number of papers and some methodological issues, a lower life-long socioeconomic position increased the risk of periodontitis in adulthood ^[6][7][18,19]. In this Special Issue, a cross-sectional study conducted with adults in London identified that periodontal disease was associated with individual and intersectional social characteristics, especially ethnicity and education ^[8][5]. Another cross-sectional study carried out among Indian adults also identified ethnicity as a relevant factor associated with periodontal disease ^[9][4]. Migration has been identified as impacting oral health. However, the way in which psychological and social factors affect migrants ^[10][20] and impact oral diseases needs to be better understood through both quantitative and qualitative research ^[10][20].

Head and neck cancer is the most common type of cancer worldwide, with projections of about half a million new cases yearly ^[11][12][13][21,22,23]. Previous research demonstrated that low income, low educational attainment, low socioeconomic position, and socio deprivation were positively associated with oral cancer ^[14][15][9,24]. In addition, a recent SR ^[16][25] reported that being from ethnic minority groups or being uninsured were related to either a delay in the diagnosis of oral cancer or a delay to start treatment. It was estimated that people affected by malignancies in the orofacial region had a substantial decrease in their oral health-related quality of life (OHRQoL), which impacted their ability to cope with daily activities ^[17][26]. More epidemiological studies evaluating the social determinants of those conditions are needed.

Traumatic dental injuries (TDI) are a public health problem because of their high prevalence and also because a traumatized tooth may impact aesthetics, quality of life, and psychosocial behavior. It was estimated that over a billion people worldwide had TDI ^[18][27]. The global prevalence of TDI is 24.2% in primary dentition ^[19][28] and 15.2% in permanent dentition ^[18][27]. Until recently, evidence of an association between socioeconomic indicators and TDI was uncertain ^[20][29]. However, an overview of SR reported that some sociodemographic characteristics (younger age, male sex, and lower-income) were associated with a higher probability of being affected by TDI ^[21][10]. In the same study, the association between TDI and the educational level of caregivers remained unclear ^[21][10]. Further primary studies are required to fully understand how inequalities affect TDI.

Temporomandibular disorders (TMD) are the main cause of non-dental orofacial pain worldwide ^[22][12] and significantly affect people’s quality of life ^[23][30]. The prevalence of TMD among children and adolescents was found to vary between 7.3 and 30.4% ^[24][31]. The proportion of adults and elderly with TMD reached 31% ^[25][32]. However, the actual prevalence of the condition is still under debate due to variations in diagnostic criteria ^[26][33]. Despite that, there are some SR providing evidence that women ^[27][26][11,33] between 20–40 years of age ^[22][12] are more likely to develop TMD. The gender-related difference could be linked to biological, cultural, and social factors, but the pathways in which these factors predispose more women than men to TMD are not yet understood. Furthermore, the role of other sociodemographic indicators, such as ethnicity and socioeconomic status, on TMD prevalence is still controversial ^[12][22].

The broad knowledge of the social determinants of oral conditions could help decision-making by healthcare providers, the development of preventive programs by policymakers, and ultimately reduce oral health inequities ^{[2][15][28][29]}[6,24,34,35].

Despite improvements in prevention, oral diseases are still a significant population problem ^[30][31][14,36], associated with oral hygiene, tobacco use, diet, and stressors. Some psychosocial factors, such as ‘self-efficacy’, ‘intention’, ‘social influences’, ‘coping planning’, and ‘action planning’, have been associated with oral hygiene ^[32][15], and studies increasingly highlight the fact that positive health behavior is influenced by psychosocial factors.

People with a higher sense of coherence (SOC) are better at managing stressful situations, problems, and promoting better general health. The SOC is a psychosocial determinant of people’s health behavior, which has been correlated to hygiene, dietary habits, and alcohol consumption ^[33][37]. An SR of nine articles aimed to analyze the empirical evidence on the association between oral health behaviors and SOC. The study identified that more favorable oral health behaviors were observed among those with higher SOC. This result suggested that SOC may be a determinant of oral-health-related behaviors, including frequency of toothbrushing, dental-care-seeking, and daily smoking habits. Mothers’ SOC could influence the oral health preventive practices of children ^[34][38]. Poursalehi et al. (2021) ^[31][36] performed an SR and meta-analysis to evaluate the effect of SOC on the oral health status of people in different age groups. The results showed that age, social support, education, working conditions, and living conditions in childhood could influence SOC. Gender did not show a significant effect on SOC. According to the authors, SOC appeared to be effective in predicting oral health behaviors.

Healthy habits such as daily toothbrushing, regular access to sources of fluoride, and moderate consumption of sugar are the most effective ways to prevent major oral diseases and to reduce health services costs ^[32][15]. According to Menegaz et al. (2018) ^[29][35], the strong social and behavioral character of oral diseases highlights the relevance of implementing educational interventions that encourage autonomy and change in health behaviors to promote prevention practices.

Scheerman et al. (2016) ^[32][15] have carried out an SR and meta-analysis of 22 papers to identify the psychosocial determinants of oral hygiene behavior in people aged 9 to 19. Higher toothbrushing frequency among adolescents was associated with a higher ‘intention’, ‘social influences’, ‘self-efficacy’, ‘action planning’, and ‘coping planning’, suggesting that these factors are likely to be psychosocial determinants of tooth brushing. In the same study, the psychosocial variables: ‘locus of control’, ‘sense of coherence’, and ‘self-esteem’ were less likely to be associated with tooth brushing. The authors highlighted the importance of psychosocial factors as determinants of oral hygiene habits among pre-adolescents and adolescents. The results of an SR developed by Calderon et al. (2014) ^[30][14] showed that ethnicity, race, and gender could affect the oral health behavior of adolescents. The results of an SR developed by Menegaz et al. (2018) ^[29][35] concluded that educational interventions promote changes in oral-health-related behaviors (daily tooth brushing, regular contact with fluoride sources, and controlled consumption of sugar), prevent major oral diseases, and reduce costs for health services and society.

It is very important that effective programs improve oral-health-related behavioral habits in different age groups. Literature indicates the need to develop research on other factors that affect oral health behavior. Future intervention trials should consider a range of psychological factors that have not been fully studied, such as ‘self-determination’, ‘anticipated repentance’, ‘action control’, and ‘self-identity’.

The access and use of dental services are relevant information to be studied in different populations. Ethnics minorities or immigrants and those from low socioeconomic groups showed lower dental services utilization globally ^[35][39]. A higher-income was consistently associated with children’s use of dental services. Among adults, 50% of the observational studies included in an SR have identified more education as a factor that increases dental service utilization ^[36][40]. In the older population, the rate of annual dental visits among those with a higher income and higher socioeconomic status is higher than among those with a lower income ^[37][38][41,42].

An SR showed that regular or preventive dental services utilization differs greatly across the globe. In countries with a higher human development index (HDI), more individuals utilize services. The utilization is also highly unequally distributed between different groups within countries. Individuals with less-supportive family structures, poor health literacy, poor general and oral health, edentulous or with severe tooth loss, and younger children show a lower utilization. Neither utilization nor its differences between groups have changed significantly with time ^[39][13]. While the burden of oral diseases is heavier on more socially vulnerable populations, access to dental services is better for those with higher socioeconomic conditions ^[36][40]. There is a positive association between dental insurance and dental visits ^[40][43]. Dentally insured adults have more regular access to dental care than the uninsured. This inequity situation increases the gap between the rich and poor. In our Special Issue, organizational and human resources factors were associated with access to dental prostheses in Brazil. Public dental offices with better organizational support and improved work incentives provided more dental prostheses to their patients. The reduction of inequalities in primary oral health care access should be set by policymakers ^[41][2].

Apart from identifying oral health determinants, it is urgent to overcome inequalities to promote health and to impact different morbidities, including oral conditions. An SR ^[42][44] evaluated intervention programs developed to reduce inequality in dental caries prevalence among children. The studied interventions included health promotion/preventive initiatives, topical fluorides, and water fluoridation to reduce caries among children of different socioeconomic groups. Comparison groups included children with an alternative or no intervention. The findings suggested that broader population interventions such as water fluoridation are more likely to reduce inequalities in children’s caries than interventions targeted at specific populations.

Studies of interventions to reduce socioeconomic inequalities ^[43][45] in dental service utilization by adults are limited to those involving pregnant women and parents organizing care for their children. They have been mostly targeted at individual behavior, rather than community or structural factors and involved participants at the lower end of the socioeconomic status spectrum. Evidence involving participants across the whole social gradient is limited.

There is a lack of research on interventions that aim to reduce socioeconomic inequalities in adult dental visits and on interventions that target community or structural causes of these inequalities. In our Special Issue, a trial identified how an integrated oral healthcare intervention for pregnant women impacted health outcomes. This study revealed that despite socioeconomic and behavioral health determining factors, multi-professional health actions during prenatal care could contribute to positive pregnancy outcomes and oral health ^[44][3]. Health policies and services availability influence inequality in services provision, while individual, social, cultural, and economic determinants affect inequality in dental services utilization ^[38][42].