Abstract
The National Oral Health Screening Program (NOHSP) is a general population-based program in Korea. The objective of this study was to assess the association between participation in the NOHSP and dental visit for periapical abscess (PA) and advanced periodontal disease (APD) among Korean adults. Data were obtained for subjects from the National Health Insurance database. The authors conducted a retrospective cohort study of 9358 randomly selected subjects who were between 40 and 64 years old in 2002. The outcomes of dental visit for PA or APD from the years 2003 to 2007 were compared between the screening and nonscreening groups. The nonscreening group had 19% higher risk of PA and 15% higher risk of APD. This study suggests that the NOHSP may decrease the risk of dental visit because of PA and APD by preventing the progress of lesion to the advanced stage among Korean adults.
Keywords
Introduction
The burden of chronic disease is rapidly increasing worldwide. In recent decades, the incidence of chronic disease has multiplied because of an increase in the average life spans, changed lifestyle, and socioeconomic developments.1,2 In the 21st century, 60% of all deaths in the world are now due to chronic diseases such as cancer, stroke, cardiovascular disease, and diabetes; 80% of chronic disease related deaths occur in low- and middle-income countries. 1 Such patterns that are observed in connection to socioeconomic factors are also observed in oral diseases such as dental caries and periodontal disease.3-5 In Korea, the distribution of oral diseases also differs according to socioeconomic status (SES). 6 In addition, the costs of treatments for oral diseases in Korea were estimated to be higher than that for many other chronic diseases in 2007. 7 Therefore, the development of a public oral health program is required as oral disease remains a major public health problem in developing countries as well as in low-income groups of developed countries.
A screening program is a public health service for the general population. It usually involves asking questions and conducting tests to identify people who are apparently healthy but may be at an increased risk of a disease or condition. 8 The benefits of a screening program include improved disease prognoses, conservation of resources, and the development of less complex treatment methods. 9 Task forces in several countries have made evidence-based recommendations for screening programs. The US Preventive Service Task Force (USPSTF) and the Canadian Task Force on the Periodic Health Examination (CTFPHE) have both recommended providing national preventive care services such as screening programs for adults or for special groups such as pregnant women or children.10,11 Australia and many countries in the European Union (EU) provide screening programs to their citizens throughout their lifetimes.8,12 The National Screening Committee and the Royal Australian College of General Practitioners recommend the guidelines for screening and preventive activities of these programs.8,12 However, these task force groups concluded that there is insufficient evidence to recommend for or against the routine oral health screening. Although the evaluations of efficacy on a mass screening program for the various diseases have been attempted,13-17 there is little convincing evidence that the oral health screening program play an important role in detecting dental caries and periodontal disease in their early stage and the ability of the oral health–screening program to reduce the morbidity or mortality of oral disease. 18 To obtain evidence for how this screening program affects their intended recipients, data from well-designed and conducted studies are needed.
The National Oral Health Screening Program (NOHSP) is a general population-based program by the National Health Insurance Corporation (NHIC) in Korea. This program includes an oral examination, oral health instructions, and a questionnaire interview. Any insured person and dependents who are at least 40 years old can receive oral health screening free of charge once every 2 years. Approximately 99% of adults in Korea are national health insurance beneficiaries. Therefore, extensive data are available from the NHIC database to study the benefits of the NOHSP. The purpose of this study was to assess the association between NOHSP and dental visits for periapical abscess and advanced periodontal disease among Korean adults who are national health insurance beneficiaries as the company employees and their dependents.
Methods
Data were obtained from NHIC for this study. National Health Insurance (NHI) is a mandatory universal health insurance program, offering comprehensive medical and dental care to the Korean population having Korean citizenship. Almost 100% of the population in Korea has been enrolled in NHI since 1989. The health insurance review and assessment service team and NHI check the requisition data, and the actual inspection is performed periodically to ascertain the authenticity of reported information.
We conducted a retrospective cohort study of 9358 subjects aged between 40 and 64 in 2002 using data on their dental visits for periapical abscess and advanced periodontal disease, which were registered in NHIC after diagnosis by dentists in clinics from 2003 to 2007. The appropriate sample size for this study was calculated using the power and sample size calculation program. 19 We planned the retrospective cohort study of a screening group and a nonscreening group with one control per case. If the true odds ratio (OR) for advanced oral disease in the screening subjects relative to the nonscreening subjects is 1.2, we need to study 4680 screening subjects and 4680 nonscreening subjects to be able to reject the null hypothesis that this OR is equal to 1 with probability (power) of .8. The type I error probability associated with this null hypothesis is .01. The selection process was as follows: (a) those who were receiving the basic living subsidy were excluded, (b) the age of those who were included ranged from 40 to 64 years, and (c) the subjects in each group were randomly selected. The subjects were randomly selected from a total of 1 710 000 people who had participated in health screening programs. The screening group was composed of 4682 subjects who were randomly selected from 450 000 who had participated in oral health and general health screening programs in 2002. The nonscreening group was composed of 4676 subjects who were randomly chosen from 1 260 000 who had participated in general health screening but not in oral health screening in 2002. Therefore, our data are representative, including personal, demographic, socioeconomic, and dental utilization information.
Rothman and Greenland 20 described that the goal of a population screening program is to reduce morbidity or mortality from disease among the screened people, and this goal is attained by early treatment of the cases discovered if early treatment can offer some advantage over late treatment. Therefore, we hypothesized that if the oral health screening program is effective, the number of late treatments for advanced disease will be lower in the screened group than in the nonscreened group. Based on this hypothesis, this study selected 2 main oral diseases at the advanced stage, periapical abscess and advanced periodontal disease, as the outcome variables. Periapical abscess is a status characterized by chronic infection and vitality loss of pulp and the formation of abscess or fistulae around the end of the root.21,22 Advanced periodontal disease is another major chronic oral disease. The symptoms of this disease are connective tissue destruction and alveolar bone loss caused by chronic inflammation in the periodontium. 23 In this study, advanced periodontal disease was defined as a case that has some subgingival calculus, formation of pocket (≥4 mm), and vertical alveolar bone loss on one or more sextants periodontium, needing gingival curettage or gingival flap operation to remove infected periodontal tissue and subgingival calculus. The code is K04.7 for periapical abscess and K05.3 for advanced periodontal disease in the codes of Korean Standard Classification of Disease, based on the International Classification of Disease of the World Health Organization. 24 When a patient with these dental problems visits a dental clinic, the dentist in the clinic should report the code of disease and the type of treatment to the NHI database electronically. We used these codes (K04.7 and K05.3) to extract data on dental visits for periapical abscess and advanced periodontal disease for this study. The 2 chronic diseases are the main cumulative oral diseases. Therefore, this study assessed the dental visit for periapical abscess and advanced periodontal disease from 2003 to 2007 as an outcome variable and whether or not the subject took part in the oral health–screening program in 2002 as an explanatory variable.
The explanatory variable was used to dichotomize the subjects into the screening and nonscreening groups. The outcome variable was used to dichotomize the subjects into those who visited for the treatment of periapical abscess and advanced periodontal disease and those who did not. Sociodemographic variables, health behaviors, and oral health status were selected as covariates. The selected variables were age, gender, monthly income, and residential district as sociodemographic information in 2002. Age was categorized into 5 groups (40-44, 45-49, 50-54, 55-59, and 60-64 years). Monthly income, which represents the SES of the study subjects, was categorized into 6 groups (≤1 000 000, 1 000 001-2 000 000, 2 000 001-3 000 000, 3 000 001-4 000 000, 4 000 001-5 000 000, and ≥5 000 001 Korean won [KRW]). Residential district was classified into 3 categories, metropolitan, city, and rural areas, which may be associated with access to dental care. The current amount of smoking and drinking frequency in 2002 were selected as health behavior information. The current amount of smoking a day was categorized into 4 groups (none, ≤10, 11-20, and ≥21 cigarettes). The alcohol drinking frequency was also categorized into 4 groups (never, 2-3 times a month, 1-2 times a week, and ≥3 times a week). Dental caries and gingivitis were selected as indicators of subjects’ oral health status in 2002. Dental caries was used to dichotomize the subjects into those who had a caries lesion in pit and fissure or on a smooth tooth surface without invasion to pulp (Yes) and those who did not (No). Dental plaque–induced gingivitis has clinical features as follows: (a) there is dental plaque at the gingival margin, (b) gingivitis starts at the margin, (c) there is a change in gingival color, and (d) there is bleeding on provocation.
The bivariate associations between the screening and dental visit was assessed by chi-square tests. The association between the screening and dental visit was analyzed using multivariate logistic regression after adjusting for the covariates. Statistical significance was determined at .01 levels. All analyses were performed using SPSS statistical package, Version 15.0 (IBM SPSS, Chicago, IL).
Results
The sociodemographic characteristics of the screening and nonscreening groups in 2002 are shown in Table 1. The proportion of male subjects was higher in the screening group (66.4%) than in the nonscreening group (63.5%), and the proportion of males was higher than females in both groups. In the screening group, the percentage of subjects in the 40- to 44-year age-group was highest (28.4%) among the various age-groups; as a whole, the proportion of subjects decreased with increase in age. In contrast, the percentage of 55- to 59-year-old subjects was highest (24.2%) in the nonscreening group and the proportion of subjects increased with decreasing age in the nonscreening group. The proportion of subjects younger than 50 years was higher in the screening group than in the nonscreening group, but the proportion of subjects aged between 55 and 64 years was lower in the screening group. The proportion of subjects from metropolitan areas was highest in screening (50.9%) and nonscreening groups (51.1%). The proportion of subjects from rural areas was 10.4% in the nonscreening group, which was higher than that in the screening group (8.3%). Whereas the proportion of those with monthly income ≤2 000 000 KRW was lower in the screening group (26.1%) than in the nonscreening group, the proportion of those with higher income was higher in the screening group.
Sociodemographic Characteristics of the Subjects According to Participation in the Oral Health Screening Program in 2002.
Abbreviations: KRW, Korean won; CI, confidence interval.
χ2 test.
Table 2 shows the health behaviors and oral health status of the screening and nonscreening groups in 2002. There was statistically significant difference in the frequency of alcohol drinking in screening and nonscreening groups (P = .001), but the other variables such as smoking and oral health status did not show significant difference in groups.
Health Behaviors and Oral Health Status of the Subjects According to Participation in the Oral Health Screening Program in 2002.
Abbreviation: CI, confidence interval.
χ2 test.
Table 3 shows the bivariate associations between participation in the oral health screening program and dental visit for periapical abscess and advanced periodontal disease. The proportions of dental visit for periapical abscess and advanced periodontal disease in the screening group were 11.0% and 43.4%, respectively, which were lower than in the nonscreening group (13.8% and 48.0%, respectively; P < .001).
Bivariate Association Between Participation in the Oral Health Screening Program and Periapical Abscess and Advanced Periodontal Disease.
Abbreviation: CI, confidence interval.
χ2 test.
The crude and adjusted ORs and 99% confidence intervals (CIs) for periapical abscess and advanced periodontal disease are shown in Table 4. The association between oral health screening and dental visit for periapical abscess and advanced periodontal disease remained significant at both univariate and multivariate logistic regression. The crude ORs (99% CI) of the nonscreening group were 1.30 (1.10-1.53) and 1.21 (1.08-1.34) for periapical abscess and advanced periodontal disease, respectively. The adjusted ORs (99% CI) of the nonscreening group were 1.19 (1.01-1.42) and 1.15 (1.02-1.28) for periapical abscess and advanced periodontal disease, respectively, after adjusting for sociodemographic variables (age, gender, residential district, and monthly income), health behaviors (current smoking status and drinking frequency) and oral health status in 2002 (dental caries and gingivitis).
Adjusted Odds Ratios and 99% Confidence Intervals of the Dental Visits for Periapical Abscess and Advanced Periodontal Disease.
Abbreviation: CI, confidence interval.
Model 1: crude odds ratios.
Model 2: adjusted for age, gender, residential district, and monthly income.
Model 3: adjusted for age, gender, residential district, monthly income, smoking, drinking, dental caries (only for periapical abscess), and gingivitis (only for advanced periodontal disease).
Discussion
The premise of screening is that for many diseases early detection improves the prognosis. 25 A disease must be detectable during the preclinical stage by some screening test, and early treatment should convey a benefit over treatment at the time when the disease would have come to attention without screening. 26 In oral health screening, the most common method of evaluating the effect of screening only for oral cancer has been comparing the survival rate among screen-detected cases with the survival rate among cases diagnosed through the occurrence of symptoms.27,28 Thus, this study was performed to assess the effectiveness of the NOHSP in Korea. Representative data related to oral health screening and utilization of dental clinic was obtained from NHIC. This study showed that subjects who do not participate in the oral health screening program may have about 1.19 times higher risk of periapical abscess than those who participate in the screening program. The risk of dental visit for advanced periodontal disease is also 1.15 times higher than in the screening group. These results mean that the nonscreening group is more likely to visit a dentist for treatment of periapical abscess and advanced periodontal disease than the screening group. Therefore, it is suggested that the oral health screening program is able to decrease dental visits for treatment of periapical abscess and advanced periodontal disease by preventing the progress of lesions to the advanced stage among adults in Korea.
This study showed that the proportion of males in the screening group was higher than that in the nonscreening group. In addition, the proportion of those younger than 55 years was higher in the screening group than in the nonscreening group. This study revealed that the proportion of those of low SES, namely, those with monthly income less than 2 000 000 KRW was higher in the nonscreening group than in the screening group. Therefore, the national public health service for oral health promotion needs to lower socioeconomic barriers so that low-SES populations may be able to access screening programs more easily. In Korea, NHIC provides the oral health screening program free of charge for the general population to achieve oral health equality. This study, however, showed that the participation rate differs according to gender, age, and the level of monthly income. Thus, we need to wage systematic public campaigns for NOHSP targeting the female, the senior, and the low-income population and to ensure that this program is equally provided to the general population regardless of income level.
Does an oral health screening program really improve oral health as our results show? One weakness in this study is a selection issue that comes from self-selection of subjects who decide to be screened. Because screening programs are voluntary, those who participate in screening may have better oral health and health behaviors and higher interest in oral health than those who refuse to be screened. 25 Therefore, observational studies on the effectiveness of screening should include potential confounders such as SES, health behaviors, and health status. Although such confounders were not considered fully for analyzing the effect of oral health screening in this study because of the strict regulation on opening the database of NHIC, we obtained the ORs and 99% CIs of the nonscreening group for periapical abscess and advanced periodontal disease adjusted for sociodemographics (age, gender, residential district, and monthly income), health behaviors (current smoking status and drinking frequency), and oral health status in 2002 (dental caries and gingivitis).
This study may have some limitations. There was no formal test for reliability of data. Furthermore, the period between the screening and the outcome was short, which may reflect some systematic differences between the screening and nonscreening groups. Also, there was relatively weak association between oral health screening and dental visit for periapical abscess and advanced periodontal disease. The results of this study, however, can still be meaningful evidence because this study was a rare attempt to assess the effectiveness of oral health screening programs and was designed as a representative and retrospective cohort study adjusting for potential confounders. One way to overcome these limitations is to evaluate oral health screening programs by adopting a more comprehensive design such as prospective cohort study or an ethical randomized controlled trial.
In conclusion, this study suggests that the oral health screening program may decrease the frequency of dental visits for treatment of periapical abscess and advanced periodontal disease by preventing the progress of lesion to the advanced stage among adults who are National Health Insurance beneficiaries as the company employees and their dependents.
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interests with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by the Health Promotion Fund, the Ministry for Health, Welfare and Family Affairs, Republic of Korea (Policy Project 09-23).