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Introduction
Periodontitis is a chronic inflammatory disease with connective tissue and bone destruction, by periodontal microbial infection1). It represents a significant public health concern, leading to considerable socio-economic consequences2). According to the Korean National Health and Nutrition Examination Survey (KNHANES), the estimated prevalence of periodontal disease was 23.4% in Korean adults3). Currently, clinical examination is the standard and preferred method for monitoring periodontitis. Nevertheless, the accurate and reproducible quantification of periodontal disease has presented considerable challenges for both oral clinicians and epidemiologists. Thus, population-level surveillance of periodontitis is challenging.
In Korea, the method used to assess periodontal disease in the KNHANES is the Community Periodontal Index (CPI), developed by the World Health Organization (WHO). However, a review of the oral examination data revealed that due to inter-investigator variability in the eighth cycle (2019-2021) KNHANES, the oral health data remained unpublished, leading to the cessation of periodontal disease assessments starting from the second year of the ninth cycle (2023) KNHANES4). Challenges encountered during periodontal examinations included the proficiency of investigators (consistent application of pressure with the CPI probe), examination conditions (adequate lighting), resource availability (dentists, time, and effort), ensuring inter-investigator consistency (lack of consistency in producing periodontal disease prevalence indicators), and subjective patient assessments (treatment-centered evaluation methods)5). Numerous factors must be considered during periodontal examinations, and practically, there are significant limitations to implementing textbook methodologies for accurate diagnosis and treatment of periodontal disease.
The self-reported questionnaire is a potential alternative strategy. The advantage is the availability of valid, cost-effective measures for periodontitis. An 8-item questionnaire was developed through collaboration between the Centers for Disease Control and Prevention (CDC) and the American Academy of Periodontology (AAP)6-8). Initiated during the 2009-2010 cycle of the National Health and Nutrition Examination Survey, the eight questions were integrated into the protocol to monitor the prevalence of periodontitis among American dentate adults aged over 30 years, serving as a substitute for clinical periodontal examinations. The CDC/AAP questionnaire has been validated in American2,9), French10), Spanish11), Dutch12), Japanese13), and Korean14,15) versions. However, this questionnaire is an older instrument developed by the CDC/AAP, necessitating an evaluation of its applicability and validity as a periodontal examination in the context of national epidemiological surveillance of oral health in Korea.
Therefore, this study aims to develop a self-reported questionnaire in Korean considering as a reference the eight self-reported periodontal questions from CCD/AAP and to assess the validity of the self-reported questionnaire in Korean adults.
Materials and Methods
1. Study participants and demographic information
This study complied with the Declaration of Helsinki, and the study protocol was approved by the Institutional Review Board (IRB)/Ethics Committee of Kyungpook National University Institutional Review Board (KNU-2024-0067). All individuals who provided informed consent were considered after receiving a full explanation of the study purpose and methods.
The oral health examination in the National Health and Nutrition Examination Survey (NHANES) is conducted across four regions: Metropolitan area 1, Metropolitan area 2, Chungcheong-Honam, and Gyeongbuk-Gyeongnam. Examinations are performed in designated oral examination rooms within mobile examination units. NHANES utilizes a complex, multistage probability sampling method to select participants. Among those selected, only individuals who voluntarily consented to participate were included in this study.
From March 5 and April 5, 2024, a total of 120 participants who underwent oral health examinations in NHANES were initially enrolled. After excluding non-respondents to the questionnaire, 119 individuals were retained as the final study sample. Inclusion criteria required participants to be 20 years or older with the ability to read and comprehend Korean. Exclusion criteria included individuals with fewer than two remaining teeth and those diagnosed with severe or terminal illnesses.
Data on age, sex, smoking, drinking, exercise, subjective oral health, oral pain experience, hypertension, and diabetes were also collected using the questionnaire. Age groups were categorized as 20-39, 40-59, 60-69, and ≥70 years. Smoking status was classified as current smoker, former smoker, or never smoker. Drinking status was categorized as ≥2 per week, 1-4 per month, <1 per month, or never a drinker. The exercise was dichotomized into yes or no.
2. Periodontal clinical examination and self-reported questionnaires for periodontitis
A total of 10 teeth were examined for each participant, which included the maxillary and mandibular left and right first and second molars, the maxillary right central incisor, and the mandibular left central incisor. If a central incisor was absent, the corresponding tooth on the opposite side was assessed instead. The periodontal condition was evaluated using a CPI probe at six specific points in each tooth’s periodontal pocket, with the highest code value recorded. The CPI codes were defined as follows: Code 0 indicates no signs of gingival inflammation; Code 1 denotes bleeding on probing; Code 2 signifies the presence of dental calculus (including calculus detected up to 4 mm below the gingival margin); Code 3 corresponds to a periodontal pocket depth of 4 mm to less than 6 mm; and Code 4 indicates a pocket depth of 6 mm or greater. Clinical periodontitis was defined as a CPI code greater than 2. The periodontal tissue examination was carried out by four dentists who were properly trained and calibrated by standardized procedures in the published manual by the WHO16). The Cohen’s κ coefficient for inter-examiner reliability among the four dentists was confirmed to be above 0.70.
A 10-item Korean version of the questionnaire was developed, based on the 8-item CDC/AAP questionnaire with the addition of two items on ‘gingival bleeding’ and ‘periodontal treatment and surgery under anesthesia’ (Table 1), along with references to previous studies conducted in Korea14,17).
The 10 items are as follows: “Do you think you might have gum disease?”, “Overall, how would you rate the health of your teeth and gums?”, “Have you ever had treatment for gum disease, such as scaling and root planning, sometimes called “deep cleaning?”, “Have you ever had any teeth become loose on their own, without an injury?”, “Have you ever been told by a dental professional that you lost bone around your teeth?”, “During the past 3 months, have you noticed a tooth that does not look right?”, “Aside from brushing your teeth with a toothbrush, in the last 7 days, how many times did you use dental floss or any other device to clean between your teeth?”, “Aside from brushing your teeth with a toothbrush, in the last 7 days, how many times did you use mouthwash or other dental rinse products that you use to treat dental disease or dental problems?”, “During the past three months, have you had bleeding gums?”, and “Have you ever had periodontal treatment or surgery with anesthesia (including deep cleaning)?”.
3. Statistical analysis
We performed the Chi-square test, independent t-tests, and one-way analysis of variance (ANOVA) analysis to understand the demographic and the self-reported periodontal questionnaire in study participants classified by the presence or absence of periodontitis and the means of CPI index. We presented continuous and categorical variables through mean±standard deviation (SD) and the number of cases (n) with percentage (%), respectively.
Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for each item of the self-reported questionnaires with adjusted demographic factors using multivariable binary logistic regression analyses. Kendall’s Tau-b correlation was used to assess the relationship between pairwise dichotomized items in the periodontal questionnaire. A model was constructed considering the correlations between each item. The performance of the predictive model was evaluated using sensitivity, specificity, the area under the curve (AUC), and the receiver operating characteristic curve (ROC).
All statistical analyses were performed in SAS 9.4 (SAS Institute, Cary, NC, USA), with a statistical significance level of 0.05.
Results
A total of 119 participants (54 men and 65 women) were analyzed to understand the characteristics of demographic factors according to the presence or absence of periodontitis and the means of CPI index, as shown in Table 2. There were no statistically significant differences between the groups except for sex and smoking. The mean CPI value for males was 1.65, which was significantly higher than that of females. The CPI mean value was 2.14, which was significantly higher than that of both former and never smokers.
Table 3 shows responses to questions according to the presence of periodontitis and CPI mean. Questions 1, 3, and 10 were significant differences in individuals who had periodontitis and higher CPI mean than other groups (CPI mean±SD; 1.548±1.253, 1.514±1.363, and 1.735±1.377, respectively) (P<0.05). As shown in Table 4, the crude odds ratios (ORs) for the presence of periodontitis in questions 1, 3, and 10 were 3.403, 4.148, and 2.676. The multivariable-adjusted odds ratio (aOR) for the presence of periodontitis in question 3 was 4.649 with a 95% CI 1.223-17.670. The higher correlations with item 3 were 0.478 for item 1 and 0.417 for item 10 among the pairwise dichotomized periodontal questionnaire items (Table 5).
In Fig. 1, model A, which included only item 3 of the self-reported questionnaire associated with periodontitis with demographic factors, demonstrated an AUC value of 0.82, with a sensitivity of 0.93 and a specificity of 0.42. Model B, which included items 1, 3, and 10 with demographic factors, yielded the next highest prediction value (AUC value of 0.86, Sensitivity 0.86, and Specificity 0.26). The AUC value of model C, which included all items with demographic factors, was 0.94 with 0.90 of sensitivity, and 0.14 of specificity.
Discussion
This study was conducted to design a questionnaire for epidemiological surveillance of periodontal disease, with the goal of continuously monitoring periodontal disease status and collecting reliable, valid, and high-quality data among Korean adults. The Korean version self-reported questionnaire for periodontal disease consists of 10 items, including 8 items developed by the CDC/AAP and 2 additional items on gingival bleeding and periodontal treatment under anesthesia. The multivariable model to evaluate the performance of the Korean version self-reported questionnaire for periodontal disease had an adjusted OR 4.649 with highest AUC 0.82 in model A (only item 3). Furthermore, Model B (included item 1, 3, and 10), and model C (included all items) had an AUC of >0.70 with high sensitivity, but low specificity. This study demonstrated that a 10-item self-reported questionnaire for periodontitis may be an effective measure for screening periodontal disease in the population, particularly questions about “Have gum disease”, “Treatment for gum diseases, such as scaling and root planning”, and “Periodontal treatment and surgery under anesthesia”.
The present study results demonstrated that certain items (items 1, 3, and 10) of the Korean version self-reported questionnaire exhibited good predictive power and can serve as a reliable and valid tool to screen individuals with periodontal disease. The three items (items 1, 3, and 10) are all directly related to periodontal disease. In particular, item 3, which asks whether the participant has received treatments such as scaling or root planning for gum disease, is a highly reliable item for identifying periodontal disease. Similar to our study, previous research has demonstrated the effectiveness of question Q3 in predicting periodontal disease18). Furthermore, the screening performance of the CDC/AAP questionnaire for periodontal disease was similar to or slightly enhanced compared to prior studies, based on AUROC, sensitivity, and specificity6,10,11,15,19). However, it may be inappropriate to compare the current results with other studies due to differences in population characteristics, sample size, case definitions, and periodontal examination protocols20). Therefore, a suitable arrangement of items should be considered, taking into account demographic variables. In our study, men and smokers had higher CPI scores. Similar to our findings, other studies examining the accuracy of periodontal disease questionnaires have also reported a strong association between males, smoking, and periodontal disease21,22). These factors have consistently shown a significant correlation with periodontal status in various populations, further supporting their role as key risk factors for periodontal disease. Additionally, while our study defined periodontal disease based on CPI measurements, a new periodontitis classification scheme defined in 201723) should be considered in future research.
This study highlights the effectiveness of self-report questionnaires in complementing the diagnosis of periodontal disease, a condition that poses challenges in ensuring inter-examiner reliability in public oral health surveillance. The use of self-reported questionnaires not only contributes to reducing costs and resource utilization but also enhances the accessibility of epidemiological surveillance. Additionally, it presents the potential for application at the national level, offering a practical solution for minimizing misclassification of periodontal disease status in large-scale population studies.
There were several limitations in this study. First, this is a cross-sectional study design with a small sample size. Nonetheless, the study provides preliminary evidence that a reliable predictive questionnaire for periodontal disease could be developed. Future studies on a self-reported questionnaire to predict periodontal diseases should include a larger population and well-designed studies such as a prospective study. Second, the Korean version self-report periodontal questionnaire, serving as an alternative to the CPI, shows statistical significance only in certain items and has low to moderate specificity. Epidemiologists and public health experts may tolerate a decrease in specificity if achieving high sensitivity is critical, provided that follow-up confirmatory tests can be utilized to minimize false positives24). Future research is needed to develop additional questions that reflect the characteristics of periodontal disease as measured by the CPI, in order to create a questionnaire with higher sensitivity and specificity for evaluating periodontal disease. Third, the severity of periodontal disease was not considered. Given that predictive ability varies according to the definition of periodontitis, this should be taken into account in future studies to assess the predictive power more accurately25). Finally, the possibility of bias from omitted variables should be considered, as the exclusion of certain confounders from the statistical models might affect the findings and lead to inaccurate interpretations.
Conclusions
This study aimed to evaluate the applicability of a self-administered questionnaire for measuring periodontitis in a population. A survey and CPI examination were conducted with 119 adult participants in South Korea, leading to the following conclusions.
1. Respondents who answered “yes” to questions 1, 3, and 10 had higher CPI scores compared to those who did not. The correlation coefficients between the questions were highest between questions 1 and 3, followed by 3 and 10. Moreover, the crude odds values for the survey questions and periodontal disease were 3.403 for question 1, 4.148 for question 3, and 2.676 for question 10. The adjusted odds ratio was significantly higher for question 3, at 4.649 times.
2. A 10-item self-reported questionnaire for periodontal disease may be an effective tool for screening periodontal disease in the population, especially considering questions such as “Have gum disease”, “Treatment for gum disease, such as scaling and root planning”, and “Periodontal treatment and surgery under anesthesia”. The area under the curve (AUC) value for this questionnaire exceeded 0.7, indicating good discriminatory power in identifying individuals with periodontal disease.
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