Literature Search Strategy

A comprehensive literature search was conducted using several electronic databases, including PubMed, MEDLINE, Scopus, and the Cochrane Library, to identify relevant studies on OHL (Table 1 ). The search strategy was designed to capture a broad range of articles related to OHL, encompassing various aspects such as its definition, measurement, impact on health outcomes, and interventions aimed at improving OHL. The search terms used included combinations of keywords and phrases such as "oral health literacy," "dental health education," "health disparities," "preventive dental practices," "health communication," and "public health." Boolean operators (AND, OR) were used to refine the search and ensure comprehensive coverage of the topic. The search was limited to peer-reviewed articles published in English from 2000 to 2024.

Study Screening

The preliminary search produced a significant quantity of articles. The initial round of screening involved evaluating the titles and abstracts of all identified publications to ascertain their pertinence to the subject of OHL. Articles that did not focus on OHL or those that were not empirical studies, were excluded at this stage. The remaining articles were then subjected to a full-text review.

Inclusion criteria

Studies should focus on OHL by either creating and validating measurement techniques, assessing the effectiveness of OHL interventions, or investigating the connection between OHL and health outcomes. Studies must incorporate empirical data, encompassing quantitative, qualitative, or mixed methodologies. Publication of articles is restricted to peer-reviewed journals. Publication of studies is required to be in the English language.

Exclusion criteria

Studies that did not focus primarily on OHL. Articles that lacked empirical data (e.g., editorials, commentaries, reviews without new data). Publications in languages other than English. Studies with significant methodological limitations that could affect the validity of their findings.

Data Extraction and Synthesis

Data from the included studies were extracted using a standardized data extraction form. The form was designed to capture key information about each study, such as author(s), publication year, country, study design, sample size, population characteristics, data collection techniques, and potential biases, was critically evaluated to provide a clearer understanding of the strengths and limitations of the research. Tools and methods used to assess OHL. Description of any interventions aimed at improving OHL, including their components, duration, and delivery methods. Primary and secondary outcomes were measured, including changes in OHL levels, oral health behaviors, and clinical oral health outcomes. Summary of the main results and conclusions of each study. Each study's design, including sampling methods.

The extracted data were then synthesized to provide a comprehensive overview of the current state of research on OHL. This synthesis involved identifying common themes and patterns across studies, as well as noting any significant differences or gaps in the literature. Where possible, quantitative data were pooled to provide aggregate estimates of the impact of OHL interventions.

Study Selection

A total of 1500 articles were identified during the preliminary literature search. Following the elimination of 1200 duplicate articles, 300 distinct articles were evaluated based on their title and abstract. Out of these, 85 articles were considered relevant and chosen for a comprehensive review of their full content. After conducting a comprehensive assessment of the whole texts, a total of 15 studies were found to meet the specific criteria for inclusion and were therefore included in the final review (Figure 1, Prisma flow chart).

Figure 1

PRISMA flowchart showing the selection process of articles retrieved from different web sources.

Reasons for Exclusion

Out of the 85 full-text articles reviewed, 70 were excluded for the following reasons: 30 articles did not focus primarily on OHL. 20 articles lacked empirical data. 10 articles were not published in peer-reviewed journals. 10 articles had significant methodological limitations.

Included Studies

The final 15 studies encompassed a diverse array of subjects pertaining to OHL, such as the creation and validation of assessment instruments, the assessment of educational and community-based interventions, and the analysis of the correlation between OHL and oral health outcomes. The studies were conducted in various countries and included diverse populations, providing a comprehensive overview of the global state of research on OHL (Table 2 ).

Definition and Measurement of OHL

The OHL involves a variety of abilities, such as the capacity to comprehend, interpret, and apply oral health information (Bridges et al. 2014a). Additionally, it encompasses the task of navigation through the healthcare system and efficiently engaging with healthcare providers (Dickson-Swift et al., 2014). However, these abilities are essential for making well-informed choices regarding oral health and executing preventative and therapeutic actions (Petersen 2009). Furthermore, the low OHL level has been linked to negative oral health outcomes, including increased prevalence of periodontal disease, dental caries, and tooth loss, as well as a worse quality of life (Firmino et al., 2017). Similarly, it is crucial to comprehend and enhance OHL in order to decrease health inequalities and advocate for fairness in oral healthcare (Horowitz, Kleinman, Atchison, Weintraub, & Rozier, 2020).

Accurate measurement of OHL is critical for assessing the extent of the problem and evaluating the effectiveness of interventions (Duell, Wright, Renzaho, & Bhattacharya, 2015). Various tools have been developed to measure OHL, each with its strengths and limitations. Moreover, these tools offer valuable insights into an individual's reading skills, comprehension capabilities, and overall understanding of oral health-related information. Despite the availability of these measurement tools, challenges remain in terms of a standardized approach to evaluating OHL across different settings and populations. Furthermore, tailoring measurement strategies to address cultural and language differences is crucial to ensure validity and relevance.Gong et al. (2007) developed and tested the TOFHLiD, which has been validated as a reliable tool for measuring OHL (Gong et al., 2007). This assessment evaluates persons' aptitude in comprehending and utilizing verbal health-related information, which is crucial for properly managing their oral health.

Similarly, the REALD has been widely used to measure OHL.Jones et al. (2007) used the REALD-30 instrument to assess OHL levels among adult dental patients. Their findings indicated that there was an association between low OHL and poor oral health outcomes, underscoring the importance of improving OHL to enhance oral health (Jones et al., 2007). Further,Sabbahi et al. (2009) developed and evaluated an OHL instrument for adults, known as the Oral Health Literacy Instrument (OHLI). This tool has been shown to be useful for assessing OHL in various populations and provides valuable understanding into the association between OHL and oral health behaviors (Sabbahi et al., 2009). Additionally, the study by Jones et al. (2013) successfully developed and validated the HeLD scale for Indigenous Australians. Conducted with 400 participants from rural Indigenous communities, the research assessed the validity and reliability of the HeLD tool through community-based interventions. The findings confirmed that the HeLD is a reliable and valid tool for measuring OHL in this population, providing a valuable resource for understanding and improving oral health literacy among Indigenous Australians.

In their study,Wong et al. (2012) created and verified the Hong Kong HKREALD-30 as a tool for assessing OHL. Moreover, the study, which involved surveying 200 parents of pediatric dental patients, provided evidence that the HKREALD-30 is a reliable and valid tool for assessing OHL in Chinese adults residing in Hong Kong (Wong et al., 2012). Furthermore, this instrument is a valuable resource for evaluating and enhancing OHL in this specific group of people, demonstrating its potential for wider use in similar situations.

Impact of OHL on Health Outcomes

Numerous studies have demonstrated a strong relationship between OHL and oral health outcomes ( ; Mialhe et al. 2022) (Baskaradoss, 2018; Kanupuru, Fareed, & Sudhir, 2015; Kridaningrat et al., 2017; Navabi, Shahravan, Behnood, & Hashemipour, 2020). Moreover, persons with higher OHL are more liable to engage in preventive action, follow treatment recommendations from healthcare professionals, and maintain better overall oral hygiene (Ramos-Gomez & Tiwari, 2021). Conversely, those with limited OHL often struggle to comprehend health information and are more susceptible to misinformation, leading to adverse health outcomes such as delayed care seeking and increased health-related anxiety (Berkman, Sheridan, Donahue, Halpern, & Crotty, 2011). For example,Vann et al. (2010) examined the impact of OHL on children's oral health outcomes by assessing the OHL of female caregivers using the REALD-30 instrument. They found that higher OHL in caregivers is related with better oral health outcome in children (Vann Jr et al. 2010). This study emphasizes the significance of directing OHL treatments towards caregivers in order to enhance children's oral health. Similarly, Macek et al. (2010) assessed the relationship between OHL and dental care utilization in adults from Baltimore, Maryland, using the BHLOHKP instrument. The OHL includes conceptual knowledge. Communication is affected by oral health literacy. Furthermore, practitioners should consider low conceptual knowledge when discussing oral health with low-income and minority patients (Macek et al., 2011). This study emphasizes that if oral hygiene education messages may be ignored the health promotion may suffer.

The research conducted by Bridges et al. (2013) emphasizes the substantial correlation between the OHL of caregivers and the oral health status of children. In addition, a study was carried out in Hong Kong involving 301 child/parent pairs from kindergartens. The researchers utilized the HKREALD-30 and HKOHLAT-P tools to assess reading levels and discovered that children with caregivers who had greater literacy levels had improved oral health (Bridges et al. 2014b). Similarly, the study conducted byMiller et al. (2010) highlights the significant impact of caregiver literacy on the oral health results of children. The study included a cross-sectional survey involving 106 pairs of caregivers and children. In addition, the caregiver's OHL was assessed using the REALD-30. The results demonstrated a notable correlation between higher caregiver OHL and a reduced prevalence of dental issues in children. These findings highlight the significance of improving caregiver literacy as a primary approach to enhance children's oral health (Miller et al., 2010). Additionally, it indicates that focused educational interventions for caregivers have the potential to greatly decrease dental disease rates in children.

Adil et al. (2020) investigated the association between parents OHL and their preschoolers' caries experiences. Using the OHLI to assess OHL, cross-sectional survey was carried out with 230 parents at Hospital HUSM in Kota Bharu, Kelantan. The results demonstrated a strong correlation between parents with greater OHL and children with lower dmft scores (Adil et al., 2020). Moreover, this finding underscores the importance of focused educational programs aimed at enhancing parental OHL in order to decrease dental caries in preschool-aged children. Similarly, the link between OHL and dental health outcomes in a Brazilian adult population was investigated by Batista et al. (2018). The study used the OHIP-14 to assess quality of life in relation to oral health in a cross-sectional survey of 248 adult patients conducted in the community. According to the results, a higher OHL is linked to better oral health, which in turn leads to better oral health practices, including less need for emergency dental treatment, and an overall better quality of life (Batista et al., 2018). Furthermore, it is crucial to improve OHL in order to improve adults' dental health and overall health.

Barriers to Improving OHL

Despite the awareness of the significance of OHL, several barriers persist in effectively addressing it within the healthcare system (Tseng et al., 2021). Time constraints during patient consultations often limit the opportunities for providers to engage in educational dialogue (Joseph-Williams, Edwards, & A, 2014). Additionally, systemic issues such as inadequate resources, lack of OHL training among healthcare professionals, and the social stigma associated with low literacy further complicate efforts to enhance OHL (Farmanova, Bonneville, & Bouchard, 2018). Moreover, cultural and language differences can also act as significant barriers (Shaw, Huebner, Armin, Orzech, & Vivian, 2009). Many educational materials and resources are not culturally sensitive or available in multiple languages, which can alienate non-English speaking populations from receiving essential health information (Gao & Mcgrath, 2011). Furthermore, patients from minority backgrounds may experience distrust towards healthcare systems, which can hinder their engagement and willingness to seek help or education (Hong, Yi, Johnson, & Adamek, 2018).

Addressing these barriers requires a multifaceted approach. Healthcare systems must facilitate environments where providers have sufficient time and resources to engage with patients effectively (Khorasani et al., 2020). Moreover, the development of culturally relevant educational materials in various languages can help bridge existing gaps and enhance OHL among diverse populations (Muller, Bilich, & Jones, 2024). Several studies have identified barriers to improving OHL and accessing dental care (Calvasina, Lawrence, Hoffman-Goetz, & Norman, 2016; Lawler et al., 2023; Muller, 2016; Sistani, Virtanen, Yazdani, & Murtomaa, 2017). For example,Holtzman et al. (2014) evaluated OHL and missed dental appointments in university-based general dentistry clinic adults. According to a community-based survey and the REALM-D with 200 adult patients, poor OHL was substantially associated with more missed dental appointments (Miller et al., 2010). This shows that increasing OHL could minimize missed appointments, emphasizing the need for educational programs to increase patient attendance and oral health outcomes. Furthermore,Gironda et al. (2013) developed a simple 20-item screener (REALMD-20) to assess adult dentistry patients' dental and medical health literacy. A cross-sectional study of 200 adult patients showed that the REALMD-20 can quickly and accurately identify low health literacy patients (Gironda et al., 2013). Similarly, this tool can improve patient outcomes by providing low-literate patients with the support and instruction they need to manage their dental health.

Interventions to Improve OHL

Interventions targeting OHL have shown promising results in improving patient understanding and engagement in their oral health (Ju et al., 2017; Kaper, Sixsmith, Reijneveld, & Winter, 2021; Parker et al., 2012). Moreover, educational programs aimed at enhancing OHL can significantly increase individuals' knowledge about oral health and empower them to make informed decisions regarding their oral care (Muller, 2016). These interventions can take various forms, including community workshops, targeted informational brochures, and personalized counseling sessions ( ; Ebrahimi and Farokhi 2022) (Jacobs, Lou, Ownby, & Caballero, 2016). Furthermore, efforts to improve OHL can take various forms, including educational programs, community-based initiatives, and policy changes that promote health equity (Mathias et al., 2023). For example,Holtzman et al. (2014) evaluated OHL and missed dental appointments in university-based dental clinic adults. A community-based survey and the REALM-D with 200 adult patients indicated that poorer OHL was substantially associated with more missed dental appointments (Holtzman et al., 2014). This suggests that focused educational programs to enhance OHL may improve dental attendance and oral health outcomes by reducing appointment non-attendance.

The research conducted by NaghibiSistani et al. (2013) evaluated OHL among adults residing in Tehran, Iran. The study employed a community-based cross-sectional survey involving 1031 participants. The study employed the OHL-AQ to determine that Iranian people had an average level of OHL. Furthermore, the results indicate that spreading evidence-based oral health information through different channels, such as dentists, radio/TV, and other health professionals, has the potential to greatly improve public OHL (Sistani et al., 2013). This highlights the need for multi-channel educational strategies to improve oral health outcomes in the population. Similarly,Parker et al. (2012) tested a functional, context-specific OHL intervention for Indigenous individuals in rural Australia. In this delayed intervention randomized controlled trial, 400 Indigenous persons aged 18 and older participated. Participants' OHL improved significantly after the context-specific intervention, according to the HeLMS (Parker et al., 2012). This suggests that culturally sensitive therapies can improve oral health in distant Indigenous groups. Furthermore,Lee et al. (2022) examined gender differences in OHL and OHRQoL in older Taiwanese individuals. The study used the OHL-AQ, MNA-SF, IADL, and OHIP-14T on 216 older persons. Additionally, OHL and OHRQoL were significantly correlated, with gender differences (Lee et al., 2022). This emphasizes the need for gender-specific interventions to improve OHL and older adults' quality of life.

The Role of Technology in Enhancing OHL

The digital age has introduced innovative methods for improving OHL through technology (Jagde et al. 2021). Online platforms, interactive applications, and webinars offer accessible resources that can equip individuals with essential oral health knowledge (Dahiya, Khanna, Dogra, & Jaglan, 2024). Research has highlighted the potential of using mobile applications to promote oral health literacy, providing users with easy access to valuable information tailored to their needs, such as appointment reminders, oral hygiene tips, and dietary guidelines (Tiffany, Blasi, Catz, & Mcclure, 2018). Moreover, e-learning modules have shown effectiveness in training healthcare providers to communicate relevant health information effectively (Lawn, Zhi, & Morello, 2017). Online platforms offer flexibility for professionals seeking to enhance their communication strategies and improve their understanding of OHL-related issues (Claflin et al., 2022). However, while technology can serve as a powerful tool for improving OHL, it is essential to consider the digital divide (Bayazıt & Bayazit, 2023). Although, access to technology varies significantly among different populations, particularly those from lower socio-economic backgrounds. Furthermore, ensuring that all individuals can access technological resources is crucial for developing equitable OHL interventions (Sharma, Mohanty, Balappanavar, Chahar, & Rijhwani, 2022).