Impact of oral health literacy on oral health behaviors and outcomes among the older adults: a scoping review
Healthy aging is increasingly recognized as a multidimensional process encompassing not only physical and mental well-being but also oral health . Oral health, which includes a range of oral diseases and conditions such as dental caries, periodontal disease, complete tooth loss, and oral cancer, plays a crucial role in overall quality of life and well-being . These conditions are not only prevalent but also have significant public health relevance . It is estimated that nearly 3.5 billion people worldwide are affected by oral diseases, with a combined global prevalence of 45%, which surpasses that of any other non-communicable diseases (NCDs) . The implications of poor oral health are profound, affecting chewing and swallowing, nutritional intake, speech, and social interactions . Additionally, it has also been linked to systemic conditions such as cardiovascular disease and diabetes, highlighting the interactions of oral and general health . Thus, the integration of oral health care into routine medical care for older adults is imperative , such as regular dental check-ups, proper oral hygiene practices, and preventive education initiatives . In recent years, oral health literacy (OHL) has emerged as a possible underlying mechanism that explains oral health in many groups . It refers to the capacity to obtain, interpret, and utilize oral health information to inform beneficial oral health prevention and treatment decisions . Research has consistently demonstrated that higher levels of OHL are associated with better oral outcomes, such as regular brushing , periodontal health  and adherence to dental appointments . Individuals with low OHL often struggle to comprehend complex health information and instructions . This lack of understanding not only affects daily oral hygiene routines but also impacts long-term dental health management, contributing to deteriorating oral conditions . Additionally, OHL mediates the effects of socioeconomic factors, with those having low OHL often experiencing lower satisfaction with life and social withdrawn . Despite the growing recognition of the impact of OHL on oral behaviors and outcomes in adults, there has been no comprehensive overview specifically addressing vulnerable older adults. This scoping review aims to synthesize existing literature on the impact of OHL on oral health behaviors and outcomes among older adults, identifying gaps in the evidence base and providing insights that can inform future research and interventions to this vulnerable population. 

Study design This review was based on the framework established by Arksey and O’Malley (2005) , which involves five key stages: (1) identifying the research questions; (2) determining relevant studies; (3) selecting studies; (4) charting the data; and (5) collating, summarizing, and reporting the results. Identifying the research questions The specific research question was formulated using the PECO model (Population, Exposure, Comparison, and Outcome) as follows: older individuals aged 60 and over (Population), oral health literacy (Exposure), no comparison group or seniors with either low or high OHL (Comparison), and any indicators of oral health outcomes or behaviors (Outcome). Consequently, the research question for this review was: “What is the impact of OHL on oral health outcomes and behaviors among the older people?” Identifying relevant studies Literature searches were conducted using PubMed, Web of Science, CINAHL, EMBASE and MEDLIINE on July 22, 2024. The keywords for the search were “oral health literacy” or “health literacy of dentistry” and “elderly” or “older adult.” The examples of the search strategy used in Web of Science were as follows: “(((((((((((((TS=(oral health literacy)) OR TS=(health literacy of dentistry)) AND TS=(elderly)) OR TS=(older adult)) AND TS=(oral health behavior)) OR TS=(toothbrush)) OR TS=(dental visit)) OR TS=(tooth flossing)) OR TS=(oral health outcome)) OR TS=(caries)) OR TS=(periodontal disease)) OR TS=(quality of life)) OR TS=(missing teeth)) AND TS=(oral hygiene).” No literature search was conducted on gray literature. The reference lists of the identified studies were also hand-searched for any other relevance studies. Eligibility criteria In this scoping review, no restrictions were applied to study design; however, the search was limited to studies published in English. The study population was restricted to individuals aged 60 years and older or the average age was within this range. Oral health literacy was defined as “the capacity of individuals to obtain, process, and understand basic oral health information and services necessary for making informed health decisions” . Oral health outcomes included any physical, psychosocial, survival, and economic aspects of oral health status and quality of life, as well as clinical or physiological measures relevant to healthcare professionals . Oral hygiene practices, nutritional choices, and patterns of dental service utilization and other behaviors are classified as oral health behavior. Prior to commencing the screening process, a calibration exercise will be conducted to ensure reliability in correctly selecting articles for inclusion . It will entail independently screening a random sample of 5% of the included citations by two reviewers. Eligibility criteria will be modified if low agreement is observed between the reviewers. The reviewers will then independently screen the remainder of the results using a pre-defined relevance criteria form for all levels of screening. Discrepancies will be resolved by discussion with a third reviewer. Charting, summarizing, and reporting the findings To characterize and summarize the results, a map of the data extracted from the included papers will be presented in a tabular form. In alignment with the objective of this study, key information, including the author’s name, publication year, location, sample size, average age, OHL assessment tool, main outcome and measurement were recorded. Two investigators independently read each article and extract the relevant data. Differences in abstraction will be resolved by discussion or the involvement of a third reviewer. We will not formally appraise methodological quality because the aim of a scoping review is to identify gaps in the evidence base and to target topic areas for future reviews. Once the data are extracted, both numerical and thematic analyses are conducted. Thematic analysis involves examining text excerpts to determine how they address the research questions and generating codes that accurately reflect the content . A provisional list of codes is created and refined iteratively throughout the data analysis process. As codes are developed, a review of their relationships to one another helps to identify patterns, ultimately leading to the formation of categories and overarching themes. 

This review was based on the framework established by Arksey and O’Malley (2005) , which involves five key stages: (1) identifying the research questions; (2) determining relevant studies; (3) selecting studies; (4) charting the data; and (5) collating, summarizing, and reporting the results. Identifying the research questions The specific research question was formulated using the PECO model (Population, Exposure, Comparison, and Outcome) as follows: older individuals aged 60 and over (Population), oral health literacy (Exposure), no comparison group or seniors with either low or high OHL (Comparison), and any indicators of oral health outcomes or behaviors (Outcome). Consequently, the research question for this review was: “What is the impact of OHL on oral health outcomes and behaviors among the older people?” Identifying relevant studies Literature searches were conducted using PubMed, Web of Science, CINAHL, EMBASE and MEDLIINE on July 22, 2024. The keywords for the search were “oral health literacy” or “health literacy of dentistry” and “elderly” or “older adult.” The examples of the search strategy used in Web of Science were as follows: “(((((((((((((TS=(oral health literacy)) OR TS=(health literacy of dentistry)) AND TS=(elderly)) OR TS=(older adult)) AND TS=(oral health behavior)) OR TS=(toothbrush)) OR TS=(dental visit)) OR TS=(tooth flossing)) OR TS=(oral health outcome)) OR TS=(caries)) OR TS=(periodontal disease)) OR TS=(quality of life)) OR TS=(missing teeth)) AND TS=(oral hygiene).” No literature search was conducted on gray literature. The reference lists of the identified studies were also hand-searched for any other relevance studies. Eligibility criteria In this scoping review, no restrictions were applied to study design; however, the search was limited to studies published in English. The study population was restricted to individuals aged 60 years and older or the average age was within this range. Oral health literacy was defined as “the capacity of individuals to obtain, process, and understand basic oral health information and services necessary for making informed health decisions” . Oral health outcomes included any physical, psychosocial, survival, and economic aspects of oral health status and quality of life, as well as clinical or physiological measures relevant to healthcare professionals . Oral hygiene practices, nutritional choices, and patterns of dental service utilization and other behaviors are classified as oral health behavior. Prior to commencing the screening process, a calibration exercise will be conducted to ensure reliability in correctly selecting articles for inclusion . It will entail independently screening a random sample of 5% of the included citations by two reviewers. Eligibility criteria will be modified if low agreement is observed between the reviewers. The reviewers will then independently screen the remainder of the results using a pre-defined relevance criteria form for all levels of screening. Discrepancies will be resolved by discussion with a third reviewer. Charting, summarizing, and reporting the findings To characterize and summarize the results, a map of the data extracted from the included papers will be presented in a tabular form. In alignment with the objective of this study, key information, including the author’s name, publication year, location, sample size, average age, OHL assessment tool, main outcome and measurement were recorded. Two investigators independently read each article and extract the relevant data. Differences in abstraction will be resolved by discussion or the involvement of a third reviewer. We will not formally appraise methodological quality because the aim of a scoping review is to identify gaps in the evidence base and to target topic areas for future reviews. Once the data are extracted, both numerical and thematic analyses are conducted. Thematic analysis involves examining text excerpts to determine how they address the research questions and generating codes that accurately reflect the content . A provisional list of codes is created and refined iteratively throughout the data analysis process. As codes are developed, a review of their relationships to one another helps to identify patterns, ultimately leading to the formation of categories and overarching themes. 

The specific research question was formulated using the PECO model (Population, Exposure, Comparison, and Outcome) as follows: older individuals aged 60 and over (Population), oral health literacy (Exposure), no comparison group or seniors with either low or high OHL (Comparison), and any indicators of oral health outcomes or behaviors (Outcome). Consequently, the research question for this review was: “What is the impact of OHL on oral health outcomes and behaviors among the older people?” 

Literature searches were conducted using PubMed, Web of Science, CINAHL, EMBASE and MEDLIINE on July 22, 2024. The keywords for the search were “oral health literacy” or “health literacy of dentistry” and “elderly” or “older adult.” The examples of the search strategy used in Web of Science were as follows: “(((((((((((((TS=(oral health literacy)) OR TS=(health literacy of dentistry)) AND TS=(elderly)) OR TS=(older adult)) AND TS=(oral health behavior)) OR TS=(toothbrush)) OR TS=(dental visit)) OR TS=(tooth flossing)) OR TS=(oral health outcome)) OR TS=(caries)) OR TS=(periodontal disease)) OR TS=(quality of life)) OR TS=(missing teeth)) AND TS=(oral hygiene).” No literature search was conducted on gray literature. The reference lists of the identified studies were also hand-searched for any other relevance studies. 

In this scoping review, no restrictions were applied to study design; however, the search was limited to studies published in English. The study population was restricted to individuals aged 60 years and older or the average age was within this range. Oral health literacy was defined as “the capacity of individuals to obtain, process, and understand basic oral health information and services necessary for making informed health decisions” . Oral health outcomes included any physical, psychosocial, survival, and economic aspects of oral health status and quality of life, as well as clinical or physiological measures relevant to healthcare professionals . Oral hygiene practices, nutritional choices, and patterns of dental service utilization and other behaviors are classified as oral health behavior. Prior to commencing the screening process, a calibration exercise will be conducted to ensure reliability in correctly selecting articles for inclusion . It will entail independently screening a random sample of 5% of the included citations by two reviewers. Eligibility criteria will be modified if low agreement is observed between the reviewers. The reviewers will then independently screen the remainder of the results using a pre-defined relevance criteria form for all levels of screening. Discrepancies will be resolved by discussion with a third reviewer. 

To characterize and summarize the results, a map of the data extracted from the included papers will be presented in a tabular form. In alignment with the objective of this study, key information, including the author’s name, publication year, location, sample size, average age, OHL assessment tool, main outcome and measurement were recorded. Two investigators independently read each article and extract the relevant data. Differences in abstraction will be resolved by discussion or the involvement of a third reviewer. We will not formally appraise methodological quality because the aim of a scoping review is to identify gaps in the evidence base and to target topic areas for future reviews. Once the data are extracted, both numerical and thematic analyses are conducted. Thematic analysis involves examining text excerpts to determine how they address the research questions and generating codes that accurately reflect the content . A provisional list of codes is created and refined iteratively throughout the data analysis process. As codes are developed, a review of their relationships to one another helps to identify patterns, ultimately leading to the formation of categories and overarching themes. 

Literature search Our search identified 2,193 articles through electronic database searches, while the reference lists of these articles yielding an extra 33 articles. After removing duplicates, 2,226 articles were deemed eligible for title and abstract screening. Of these, 21 articles met the criteria for full-text review following the application of our inclusion and exclusion criteria. After a thorough full-text analysis, a total of 10 articles being included for qualitative synthesis in this scoping review. The study selection and screening process is detailed in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flowchart , as illustrated in Fig. . Characteristic of the studies Given the nature of our research question, cross-sectional studies are considered the most appropriate design for investigating the influence of OHL on oral health outcomes and behaviors. Consequently, all studies included in our scoping review were cross-sectional. Of the 10 articles reviewed , all were cross-sectional studies involving a total of 3,338 older participants. Sample sizes ranged from 76 to 450 across studies. The majority of these studies were conducted in Thailand, accounting for 50% of the total. The remaining studies were conducted in Colombia, Indonesia, Brazil, China, and India, each comprising the other 50%. One study focused on participants from institutional settings , while the remaining studies recruited older participants from the community, specifically those aged 60 years or older (Table ). OHL assessment Most studies assessed OHL using the Health Literacy in Dentistry (HeLD) framework. Specifically, one study utilized the HeLD-29 , while two other studies employed the short version, HeLD-14 . Three studies used the Thai version of HeLD (HeLD-Th) . One study used the Oral Health Literacy Adult Questionnaire (OHL-AQ) . Additionally, the Short Test of Functional Health Literacy in Dentistry for Older Adults (OA-TOFHLiD)  and the REALD-30  were used in separate studies. One article  adapted an oral health literacy questionnaire specifically designed for the older adults. All these instruments evaluate OHL based on a summation of scores, with higher scores indicating a greater level of OHL. Oral health outcomes Oral health outcomes identified in our search were as follows: periodontitis, number of remaining teeth or losing teeth, dental prosthesis, dissatisfaction with oral health, oral hygiene, and oral health-related quality of life. Periodontitis Two studies investigated the relationship between OHL and periodontitis by assessing the Community Periodontal Index (CPI). Piyakhunakorn et al.  indicated statistically significant associations between severe periodontitis and low OHL ( p = 0.029) and in the study of Chowdary et al. , OHL scores showed a negative correlation with periodontal status ( p = 0.048). Number of remaining teeth and losing teeth Two articles sought to determine the association between OHL and the number of remaining teeth (NRT) or tooth loss in the older population. Sermsuti et al.  demonstrated a significant association between limited OHL and having fewer than 20 remaining teeth (odds ratio [OR] = 1.986, p = 0.018). In contrast, Mafla et al.  found no significant effect of OHL on the number of lost teeth after controlling for potential covariates ( p = 0.519). Dental prosthesis The relationship between OHL and dental prosthesis has been investigated in two studies. Mafla et al.  found a significant positive association between OHL and the number of replaced teeth ( β = 0.65, 95% CI: 0.52–0.78, p < 0.001) while Chowdary et al.  revealed a significant negative correlation between OHL and prosthetic needs ( p < 0.01), suggesting that individuals with lower OHL are more likely to require prosthetic interventions. Dissatisfaction with oral health (DOH) One study examined the impact of OHL on DOH. Multivariable regression analysis revealed that individuals with low OHL had 1.28 times higher odds of experiencing DOH compared to those with high OHL, even after adjusting for sociodemographic, economic, and health-related factors ( p = 0.047) . Oral hygiene Two studies evaluated the correlation between OHL and oral hygiene, as measured by the Simplified Oral Hygiene Index (OHI-S). Kridaningrat et al.  found no significant correlation between OHL and OHI-S scores ( p = 0.36) while Chowdary et al.  reported that better oral hygiene status was significantly associated with higher OHL scores ( p < 0.05). Oral Health-related quality of life (OHRQoL) In one study, the short-form Oral Health Impact Profile (OHIP-14T) was used to assess participants’ OHRQoL. Lee et al.  identified a significant association between OHL and OHRQoL among men (OR = 1.809, p = 0.006), but not among women (OR = 0.885, p = 0.186), after controlling for age, nutrition, education level, and other covariates. Oral health behavior Oral health behavior identified in the four articles in our search were as follows: health information seeking behavior, oral health-related behaviors, such as toothbrushing, dental flossing, and dental check-up. Health information seeking behavior (HISB) The relationship between OHL and HISB is underexplored in the existing literature. In one study by Lee et al. , the majority of older participants exhibited HISB (57.3%). However, no significant association was found ( p > 0.05). Oral health-related behaviors Three studies investigated the associations between OHL and oral health-related behaviors among older adults. Piyakhunakorn et al.  examined various behaviors, including tooth brushing frequency, brushing duration, and dental visits within the past 12 months. Their regression analysis revealed that participants who brushed their teeth less than twice daily were more likely to have lower OHL scores (OR = 1.905, p = 0.047), which is consistent with the study of Chowdary et al. . Additionally, Khamrin et al.  explored a broader range of oral health behaviors, including tooth brushing, flossing, dental check-ups, and consumption of healthy foods. Their findings indicated a positive association between OHL and these oral health behaviors among the older individuals ( p < 0.05). 

Our search identified 2,193 articles through electronic database searches, while the reference lists of these articles yielding an extra 33 articles. After removing duplicates, 2,226 articles were deemed eligible for title and abstract screening. Of these, 21 articles met the criteria for full-text review following the application of our inclusion and exclusion criteria. After a thorough full-text analysis, a total of 10 articles being included for qualitative synthesis in this scoping review. The study selection and screening process is detailed in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flowchart , as illustrated in Fig. . 

Given the nature of our research question, cross-sectional studies are considered the most appropriate design for investigating the influence of OHL on oral health outcomes and behaviors. Consequently, all studies included in our scoping review were cross-sectional. Of the 10 articles reviewed , all were cross-sectional studies involving a total of 3,338 older participants. Sample sizes ranged from 76 to 450 across studies. The majority of these studies were conducted in Thailand, accounting for 50% of the total. The remaining studies were conducted in Colombia, Indonesia, Brazil, China, and India, each comprising the other 50%. One study focused on participants from institutional settings , while the remaining studies recruited older participants from the community, specifically those aged 60 years or older (Table ). 

Most studies assessed OHL using the Health Literacy in Dentistry (HeLD) framework. Specifically, one study utilized the HeLD-29 , while two other studies employed the short version, HeLD-14 . Three studies used the Thai version of HeLD (HeLD-Th) . One study used the Oral Health Literacy Adult Questionnaire (OHL-AQ) . Additionally, the Short Test of Functional Health Literacy in Dentistry for Older Adults (OA-TOFHLiD)  and the REALD-30  were used in separate studies. One article  adapted an oral health literacy questionnaire specifically designed for the older adults. All these instruments evaluate OHL based on a summation of scores, with higher scores indicating a greater level of OHL. 

Oral health outcomes identified in our search were as follows: periodontitis, number of remaining teeth or losing teeth, dental prosthesis, dissatisfaction with oral health, oral hygiene, and oral health-related quality of life. Periodontitis Two studies investigated the relationship between OHL and periodontitis by assessing the Community Periodontal Index (CPI). Piyakhunakorn et al.  indicated statistically significant associations between severe periodontitis and low OHL ( p = 0.029) and in the study of Chowdary et al. , OHL scores showed a negative correlation with periodontal status ( p = 0.048). Number of remaining teeth and losing teeth Two articles sought to determine the association between OHL and the number of remaining teeth (NRT) or tooth loss in the older population. Sermsuti et al.  demonstrated a significant association between limited OHL and having fewer than 20 remaining teeth (odds ratio [OR] = 1.986, p = 0.018). In contrast, Mafla et al.  found no significant effect of OHL on the number of lost teeth after controlling for potential covariates ( p = 0.519). Dental prosthesis The relationship between OHL and dental prosthesis has been investigated in two studies. Mafla et al.  found a significant positive association between OHL and the number of replaced teeth ( β = 0.65, 95% CI: 0.52–0.78, p < 0.001) while Chowdary et al.  revealed a significant negative correlation between OHL and prosthetic needs ( p < 0.01), suggesting that individuals with lower OHL are more likely to require prosthetic interventions. Dissatisfaction with oral health (DOH) One study examined the impact of OHL on DOH. Multivariable regression analysis revealed that individuals with low OHL had 1.28 times higher odds of experiencing DOH compared to those with high OHL, even after adjusting for sociodemographic, economic, and health-related factors ( p = 0.047) . Oral hygiene Two studies evaluated the correlation between OHL and oral hygiene, as measured by the Simplified Oral Hygiene Index (OHI-S). Kridaningrat et al.  found no significant correlation between OHL and OHI-S scores ( p = 0.36) while Chowdary et al.  reported that better oral hygiene status was significantly associated with higher OHL scores ( p < 0.05). Oral Health-related quality of life (OHRQoL) In one study, the short-form Oral Health Impact Profile (OHIP-14T) was used to assess participants’ OHRQoL. Lee et al.  identified a significant association between OHL and OHRQoL among men (OR = 1.809, p = 0.006), but not among women (OR = 0.885, p = 0.186), after controlling for age, nutrition, education level, and other covariates. 

Two studies investigated the relationship between OHL and periodontitis by assessing the Community Periodontal Index (CPI). Piyakhunakorn et al.  indicated statistically significant associations between severe periodontitis and low OHL ( p = 0.029) and in the study of Chowdary et al. , OHL scores showed a negative correlation with periodontal status ( p = 0.048). 

Two articles sought to determine the association between OHL and the number of remaining teeth (NRT) or tooth loss in the older population. Sermsuti et al.  demonstrated a significant association between limited OHL and having fewer than 20 remaining teeth (odds ratio [OR] = 1.986, p = 0.018). In contrast, Mafla et al.  found no significant effect of OHL on the number of lost teeth after controlling for potential covariates ( p = 0.519). 

The relationship between OHL and dental prosthesis has been investigated in two studies. Mafla et al.  found a significant positive association between OHL and the number of replaced teeth ( β = 0.65, 95% CI: 0.52–0.78, p < 0.001) while Chowdary et al.  revealed a significant negative correlation between OHL and prosthetic needs ( p < 0.01), suggesting that individuals with lower OHL are more likely to require prosthetic interventions. 

One study examined the impact of OHL on DOH. Multivariable regression analysis revealed that individuals with low OHL had 1.28 times higher odds of experiencing DOH compared to those with high OHL, even after adjusting for sociodemographic, economic, and health-related factors ( p = 0.047) . 

Two studies evaluated the correlation between OHL and oral hygiene, as measured by the Simplified Oral Hygiene Index (OHI-S). Kridaningrat et al.  found no significant correlation between OHL and OHI-S scores ( p = 0.36) while Chowdary et al.  reported that better oral hygiene status was significantly associated with higher OHL scores ( p < 0.05). 

In one study, the short-form Oral Health Impact Profile (OHIP-14T) was used to assess participants’ OHRQoL. Lee et al.  identified a significant association between OHL and OHRQoL among men (OR = 1.809, p = 0.006), but not among women (OR = 0.885, p = 0.186), after controlling for age, nutrition, education level, and other covariates. 

Oral health behavior identified in the four articles in our search were as follows: health information seeking behavior, oral health-related behaviors, such as toothbrushing, dental flossing, and dental check-up. Health information seeking behavior (HISB) The relationship between OHL and HISB is underexplored in the existing literature. In one study by Lee et al. , the majority of older participants exhibited HISB (57.3%). However, no significant association was found ( p > 0.05). Oral health-related behaviors Three studies investigated the associations between OHL and oral health-related behaviors among older adults. Piyakhunakorn et al.  examined various behaviors, including tooth brushing frequency, brushing duration, and dental visits within the past 12 months. Their regression analysis revealed that participants who brushed their teeth less than twice daily were more likely to have lower OHL scores (OR = 1.905, p = 0.047), which is consistent with the study of Chowdary et al. . Additionally, Khamrin et al.  explored a broader range of oral health behaviors, including tooth brushing, flossing, dental check-ups, and consumption of healthy foods. Their findings indicated a positive association between OHL and these oral health behaviors among the older individuals ( p < 0.05). 

The relationship between OHL and HISB is underexplored in the existing literature. In one study by Lee et al. , the majority of older participants exhibited HISB (57.3%). However, no significant association was found ( p > 0.05). 

Three studies investigated the associations between OHL and oral health-related behaviors among older adults. Piyakhunakorn et al.  examined various behaviors, including tooth brushing frequency, brushing duration, and dental visits within the past 12 months. Their regression analysis revealed that participants who brushed their teeth less than twice daily were more likely to have lower OHL scores (OR = 1.905, p = 0.047), which is consistent with the study of Chowdary et al. . Additionally, Khamrin et al.  explored a broader range of oral health behaviors, including tooth brushing, flossing, dental check-ups, and consumption of healthy foods. Their findings indicated a positive association between OHL and these oral health behaviors among the older individuals ( p < 0.05). 

A simple answer to the question of why OHL is important is that poor or low OHL contributes to diseases, especially in the older population . A mismatch between the literacy skills of older individuals and the demands of oral health services may erect an unnecessary barrier to preventive oral care and treatment. This is the first scoping review to summarize the OHL among the older population and correlate the effects of OHL on their oral health status and behaviors. To begin with, broader definitions of OHL necessitate a specific focus on how OHL is measured comprehensively. Due to the heterogeneity among studies in assessment tools, a statistical pooling of the general level of OHL among the older people has not been feasible. Some assessment tools have faced similar criticisms as those directed at general health literacy measures . We identified that the most frequently utilized tools are based on HeLD framework, including HeLD-29, HeLD-14, and HeLD-Th. HeLD recognizes the multidimensional nature of OHL by incorporating communication, access, receptivity, understanding, and utilization, all of which have been shown to influence oral health status . Most OHL assessment tools for older adults are predominantly focused on word recognition, numeracy, and reading skills , rather than on how these abilities translate into health behaviors and service utilization. Recent advancements have sought to incorporate additional dimensions, such as decision-making and service navigation . The inclusion of these aspects is anticipated to enhance the validity of these tools as comprehensive measures of OHL, while also being adapted for older populations to ensure acceptability and cultural competence. A growing body of evidence linking oral diseases with systemic conditions suggests that the detrimental consequences of poor oral health extend far beyond the mouth . In this review, periodontal status was identified as the most frequently reported outcome among the included studies. This prominence is understandable given that the prevalence of periodontium destruction increases with aging . Furthermore, periodontal disease has been shown to have systemic implications, such as increasing the risk of cardiovascular disease and diabetes, which are particularly concerning for older adults who may already be managing multiple health conditions . Both studies identified in this review demonstrated a significant correlation between OHL and periodontal diseases both in community-dwelling and institutionalized older adults . Research explained that higher OHL is associated with better oral hygiene practices and greater adherence to preventive practices, which in turn helps in managing and preventing periodontal disease . Individuals with low OHL are less likely to recognize early symptoms of gum disease or follow through with recommended treatments . Periodontal disease is similarly chronic in nature; patient understanding and compliance are essential for successful long-term maintenance and periodontal stability . The number of remaining teeth (NRT) and tooth loss are critical determinants of both oral and general health, significantly impacting functional ability, physical symptoms, social functioning, and overall quality of life . Maintaining at least 20 residual teeth is often used as a key indicator of oral health in older adults, reflecting adequate chewing function and overall dental well-being . Research by Sermsuti et al.  found that individuals with poor OHL are significantly correlated with fewer remaining teeth. This finding aligns with previous studies linking limited OHL to increased tooth loss and deteriorated oral health . Lower OHL often reflects inadequate oral practices, e.g., infrequent brushing and flossing, and delayed dental care, which contribute to increased tooth loss . However, Mafla et al. reported no significant effect . This variation might be due to differences in oral health support and services across regions. Inadequate oral health support and limited understanding of oral care in some areas may exacerbate the risk of poor oral health outcomes, including tooth loss, highlighting the need for improved education and accessible dental care services. The correlation between OHL and prosthetic needs and oral prosthetics demonstrates a statistical significance . It is plausible that higher OHL promotes the utilization of dental health services, thereby increasing the uptake of prosthetic therapies. Another explanation is that, the failure to replace lost teeth may impair masticatory function . The top-down control from the brain to the stomatognathic system, such as masticatory function, has been established . Thus, it is tempting to think that improving masticatory function by prosthetics may be a new path for ameliorating cognitive decline, which facilitates to improve OHL . Oral health satisfaction is widely regarded as a valuable subjective measure of an individual’s oral health . Tenani et al.  demonstrated that low OHL was associated with dissatisfaction regarding oral health, even after adjusting for other covariates. Such dissatisfaction often correlates with inadequate oral health management and limited understanding of effective dental care practices . Conversely, individuals with higher OHL are better equipped to comprehend and utilize health information, leading to more proactive dental care and higher satisfaction with their oral health. Chowdary et al. demonstrated a significant association between low OHL scores and poor oral hygiene , which has been reported in previous studies . This is consistent with the understanding that effective OHL equips individuals with the knowledge necessary to engage in and sustain beneficial oral hygiene practices . Conversely, Kridaningrat et al. found no significant correlation between OHL and oral hygiene scores among institutionalized individuals . This discrepancy stresses that institutionalized older adults often face unique challenges, including substantial tooth loss and worsening oral health, which requires reconsideration to better address the special oral healthcare needs of this group. OHRQoL reflects an individual’s subjective assessment of their oral health and its impact on daily oral functioning . Lee et al. found that an increase in OHL scores is significantly associated with improvements in OHRQoL among males . However, it is worth noting that this association was not statistically significant within the female subgroup, which highlights the need for a nuanced understanding of how OHL impacts different demographics. It is possible that factors such as cultural, social, or biological differences might influence the effectiveness of OHL in improving OHRQoL for females . There is a notable scarcity of research specifically exploring how OHL affects oral health behaviors among the aging population. Tooth brushing emerged as the most frequently examined self-care oral behavior in this review, which recognized as the primary method to reduce dental plaque and gingivitis . The findings indicate that older individuals with lower OHL were more likely to brush their teeth less frequently , which presents the same way as the existing evidence . These results underscore the necessity of enhancing OHL to encourage regular tooth brushing among the older population. However, no significant correlation was found between toothbrush duration and OHL . This may be attributed to reduced manual dexterity in older adults, which hinders the ability to maintain adequate brushing duration . Thus, for this vulnerable group, adapting toothbrush handles with assistive devices or other adaptations could be beneficial . Although significant correlation between OHL and regular dental care visits has been proposed in adult population , we failed to draw this conclusion in older group . One explanation may be the lack of detailed information regarding the nature of the dental visit (preventive versus problem-based). Our data only recorded whether a dental visit occurred, without specificity on the type, setting, or purpose of the visit. Another possible explanation is the ineffective communication between doctor to older patients , which reminds that interventions should be tailored to accommodate patients’ existing OHL levels while also seeking to improve OHL through enhanced provider-patient interaction . In summarizing the current findings, it is evident that OHL appears to impact effective self-care oral behaviors in older population. However, the strength of this association may be underrepresented due to measurement tools and the limited availability of research in this area. Strengths and limitations Publication bias is a concern, as the search was restricted to articles published in English, potentially excluding more relevant studies. Unlike systematic reviews, quality assessment of the identified articles is not a mandatory step in conducting a scoping review. Moreover, most studies included in this review reported associations rather than causation between exposure and outcome variables. Therefore, there is a need for robust longitudinal studies to investigate the causal links between OHL and oral health behavior and status among the older population. One of the key limitations in current research is the variation in OHL measurement tools across studies. This inconsistency limits the comparability of results and draws definitive conclusions about the OHL in older adults. Future research should prioritize more standardized and validated instruments for measuring OHL in this specific population, which will ensure more reliable and valid understanding of the impact of OHL. 

Publication bias is a concern, as the search was restricted to articles published in English, potentially excluding more relevant studies. Unlike systematic reviews, quality assessment of the identified articles is not a mandatory step in conducting a scoping review. Moreover, most studies included in this review reported associations rather than causation between exposure and outcome variables. Therefore, there is a need for robust longitudinal studies to investigate the causal links between OHL and oral health behavior and status among the older population. One of the key limitations in current research is the variation in OHL measurement tools across studies. This inconsistency limits the comparability of results and draws definitive conclusions about the OHL in older adults. Future research should prioritize more standardized and validated instruments for measuring OHL in this specific population, which will ensure more reliable and valid understanding of the impact of OHL. 

The role of OHL in influencing oral health behaviors and outcomes in adult populations is well-documented, yet its impact on older adults remains underexplored. This review reveals a noticeable scarcity of studies addressing OHL in older populations, which suggests that OHL has not been prioritized in strategies aimed at improving oral health for this vulnerable group. This is particularly concerning given the unique oral health challenges faced by older adults. Several key gaps have emerged in our understanding of OHL among older adults, i.e., the development of age-appropriate OHL assessment tools, a stronger evidence base linking OHL to specific oral health behaviors and outcomes, and the integration of senior OHL into broader health initiatives and researches. 

