Introduction: Oral health literacy (OHL) significantly influences oral health behavior (OHB) and plays a crucial role in effective oral health promotion and achieving improved outcomes. This research aims to develop a measurement tool for evaluating OHL, named 'OHL-Ortho', and OHB in orthodontic patients. Furthermore, the study explores the extended causal relationship model from OHL to OHB.
Methods: A cross-sectional exploratory study was conducted between February and June 2023 among Thai working-age adults undergoing fixed orthodontic appliances. Participants were randomly selected and stratified from diverse healthcare facilities. OHL and OHB questionnaires were developed and subjected to confirmatory factor analysis (CFA). Descriptive statistics and Structural Equation Modeling (SEM) were utilized to analyze data and evaluate the causal relationship from OHL to OHB.
Results: The sample consisted of 321 participants, with an average age of 28.44 ± 7.56 years. Regarding construct validity, the 31-item OHL Scale achieved an overall Cronbach’s alpha of 0.97, with factor loadings ranging from 0.52 to 0.85. Similarly, the 14-item OHB Scale achieved an overall Cronbach’s alpha of 0.89, displaying factor loadings ranging from 0.42 to 0.64. Additionally, the causal relationship model of OHB aligned with empirical data, indicating that OHL exhibited a highly significant positive direct effect on OHB at a level of 0.01 (effect size = 0.81), explaining 66.00% of the variance in OHB.
Conclusion: The developed scales serve as high-quality assessment tools for healthcare providers. The study underscores the significant impact of OHL on OHB among orthodontic patients.
Introduction
Orthodontic treatment is essential for correcting dental misalignments and achieving an aesthetically pleasing and healthy smile1. However, orthodontic patients face challenges in maintaining optimal oral hygiene due to the presence of braces, wires, and other orthodontic appliances2. The accumulation of plaque around brackets and wires creates a conducive environment for bacterial growth, increasing the risk of periodontal disease among orthodontic patients3. A study by Ramamurthy and Gopalasamy4 reported that as high as 76% and 9% of patients undergoing orthodontic treatment had chronic gingivitis and periodontitis, respectively. Zachrisson et al.5 also discovered that patients experienced mild to moderate gingivitis within 1-2 months of placing the orthodontic appliance, even after previously maintaining excellent oral hygiene. Moreover, an increase in the mean values of the Plaque Index and Sulcus Bleeding Index was found after the placement of a fixed orthodontic appliance6. Therefore, periodontal disease remains a significant concern for individuals undergoing orthodontic treatment.
To mitigate the risks of periodontal disease during orthodontic treatment, adopting good oral health behavior (OHB) is of utmost importance. OHB is one example of freestanding behaviors, which are personal or lifestyle actions that individuals can modify independently to improve health and prevent illness7. Patients must maintain a diligent oral hygiene routine, incorporating proper brushing techniques to clean around brackets and wires effectively. Additionally, the use of interdental brushes, superfloss, or proxabrushes can aid in removing plaque and debris from hard-to-reach areas. Emphasizing the importance of regular dental check-ups and professional cleanings can further prevent the progression of these oral diseases, ensuring optimal oral health outcomes for orthodontic patients8.
Oral health literacy (OHL) is a key factor influencing oral health behavior. It has been developed from the concept of Health Literacy (HL), which refers to the ability to perform basic reading and numerical tasks necessary to navigate the health care environment and act on health care information , and it holds the capability to promote sustained behavior change7,9. HL is a highly prioritized concept in Thailand, highlighted within the country's Twenty-Year National Strategic Plan for Public Health for the years 2017-2036. The concept of HL has been applied in various public health areas, including oral health, leading to the development of OHL. OHL has been defined as the degree to which individuals have the capacity to obtain, process, and understand basic oral health information and services needed to make appropriate health decisions and act on them10. Various Studies show that higher oral health literacy correlates with improved preventive behaviors, such as regular brushing, flossing, and dental check-ups11-14. On the contrary, low oral health literacy is linked to a higher risk of dental issues and inadequate oral health behaviors15. Understanding this relationship is crucial for effective oral health promotion and interventions, leading to improved oral health outcomes and overall well-being.
In a previous study, Wehmeyer and colleagues explored the association between oral health literacy and periodontal disease16. Similar findings were corroborated by Holtzman et al.17 and Singh et al.18. However, the measurement tool used in their research only focused on functional literacy, utilizing the Rapid Estimate of Adult Literacy in Dentistry-30 (REALD-30) 19 and Test of Functional Health Literacy in Dentistry (ToFHLiD)20, which focus solely on word recognition. Moreover, oral health behavior in orthodontic patients, involving instruments and cleaning techniques, was rather complex compared to that of the general population. Therefore, a specific questionnaire for orthodontic patients is more appropriate. There was a previous study that constructed the OHL tool for orthodontic patients, Ortho-3021; however, it covered only word recognition which is the component of functional literacy. To the best of our knowledge, there was no OHL tool that assessed OHL to prevent periodontal disease while considering cognitive and social skills, covering all functional, interactive, and critical literacy levels in orthodontic patients. Furthermore, there are currently no OHL screening tools available for orthodontic patients from healthcare units and the Thailand Bureau of Dental Health.
Hence, the objective of this research is to develop a specialized measurement tool for evaluating OHL, named ‘OHL-Ortho’, and OHB in adult orthodontic patients undergoing fixed orthodontic appliance. Additionally, this research explores the causal relationships model that extends from OHL to OHB. Under the research hypothesis, both the measurement model and the causal relationship model align consistently with the empirical data.

Dental Health and healthcare units can utilize these 'OHL-Ortho' and OHB scales to assess the levels of OHL and OHB among adult orthodontic patients. The study's findings highlight that increasing OHL levels through government initiatives for adult orthodontic patients could result in a significant 66% improvement in OHB. Healthcare providers and professionals can arrange educational activities designed to enhance individuals' OHL, empowering them to actively improve their oral health.