Effect of the oral examinations in the national health screening program on preventive oral health care and treatments: a 19-year follow-up study

Abstract

Objectives

The national health screening (NHS) program in Korea serves as primary prevention by detecting oral diseases early for easier management. Dental scaling helps prevent oral disease and treat early periodontal disease. This study evaluated the effects of national oral examinations (NOE) in NHS on preventive oral hygiene care and dental treatments for a 19-year follow-up study.

Methods

We conducted a longitudinal observation of Korean adults ≥ 19 years between 2002 and 2003 from the Korean National Health Insurance Service (n = 4,669,107; men = 2,518,704; women = 2,150,403). The independent variable involved tracking the number of people who underwent the NOE recruited between 2002 and 2003 from 2002 to 2013. The dependent variables pertained to the number of dental scaling and the presence or absence of periodontal and dental caries treatments from 2014 to 2020.

Results

Individuals receiving 6 to 7 dental scaling during the follow-up exhibited an adjusted odds ratio (AOR) of 2.91 in the NOE-middle (3–4 times) and 3.30 in the NOE-high (5–6 times) (p < 0.001). The adjusted rate ratios were 1.69 in the NOE-middle and 1.77 in the NOE-high (p < 0.001). The AOR for periodontal treatment was 1.23 in the NOE-middle and NOE-high (p < 0.001).

Conclusion

Frequent NOEs lead to undergoing dental scaling and dental treatment, highlighting the importance of encouraging NOE attendance to improve population oral health. Expanding the scope of dental coverage for preventive intervention combined with NOE could help encourage greater participation and promote preventive oral healthcare.

Introduction

Poor oral health is a worldwide public health issue associated with unhealthy diets, social inequalities, and quality of life [1–4]. Oral disease imposes a substantial socioeconomic burden with a significant psychological impact on individuals, communities, and health services [5, 6]. According to the data from the Health Insurance Review and Assessment Service in Korea, oral diseases, including periodontal disease and dental caries, have consistently ranked as the most prevalent non-communicable diseases among individuals with outpatient visits [7, 8].

Oral preventive care with regular management and nonsurgical treatments are cost-effective methods for the early prevention of oral diseases. A previous systematic review showed that patients on long-term periodontal maintenance, including dental scaling, demonstrated no tooth loss [9]. Additionally, several studies emphasize the importance of oral preventive care due to the close relationship between oral health and overall health [10, 11]. Chen et al. [12] showed that patients who received dental scaling for five consecutive years had a significantly lower risk of developing Parkinson’s disease than those who did not undergo scaling. Early and regular dental scaling is crucial to prevent oral and systemic diseases. The government has proposed oral health policies as part of public oral health initiatives for the early prevention of oral diseases, and the World Health Organization also emphasizes the significance of oral preventive care.

Dental scaling is a part of the initial phase of periodontal disease treatment and oral disease prevention. In Korea, it typically refers to supragingival scaling, a nonsurgical periodontal treatment to prevent periodontal disease, remove plaque and calculus to address early-stage periodontitis, and reduce inflammation [13, 14]. Since 2013, the South Korean government has implemented insurance coverage for annual full-mouth dental scaling procedures in adults as part of its national health policy objectives. Health screening is pivotal for the early detection and treatment of diseases. It effectively mitigates the economic burden of medical expenses and enhances the quality of life and overall health status. National health screening (NHS) in Korea began in 1980 and is now offered free of charge to all over one year of age [15]. The NHS encompasses a wide range of health screening including national health examination, national oral examinations (NOE), health behaviors, consultations, and education at nationally designated check-up institutions [16]. In South Korea, adults can receive the NHS with NOE every two years free of charge. This screening program is part of the national health insurance system and is designed to promote preventive oral health care for adults on a biennial basis. Guaranteed health insurance and health screening help improve oral and systemic health and alleviate economic burdens, enabling universal access to dental and medical services and enhancing the accessibility of healthcare services [17].

Research on oral health care with the NOE is scarce. Additionally, a prior study on the relationship between preventive health screening and preventive care has been cross-sectional, which limits their ability to establish causal relationships or track changes over time. Longitudinal research allows for a more comprehensive understanding of how national oral health screening impacts oral health care over extended periods, highlighting the potential cumulative benefits and identifying early indicators of oral health deterioration. This long-term study with large-scale sample sizes is critical in understanding the sustained effects of preventive interventions and in demonstrating significant epidemiological relationships, particularly in aging populations. Thus, this study aimed to analyze the effect of the NOE on preventive oral healthcare among Korean adults through a 19-year follow-up study using the Korean National Health Insurance Service (KNHIS) data. The results may enhance the understanding of this process, guide policy decision-making, increase interest in preventive oral healthcare, and attenuate oral health inequalities.

Materials and methods

Study design and data source

We conducted a retrospective population-based cohort study using the KNHIS-customized data from 2002 to 2020, which was the total period of the available dataset. Since 2002, Korean national health insurance has provided coverage for the entire Korean population of 50 million, facilitated through either the National Health Insurance System (97%) or Medical Aid (3%) [18, 19]. The KNHIS data, as claims data, are generated when healthcare providers submit reimbursement requests to the Health Insurance Review and Assessment Service (HIRA) for medical expenses covered by national health insurance, following the provision of healthcare services to patients. This dataset contains records of dental and medical treatment information requested by researchers and collected by the National Health Insurance Corporation. The database is based on the date of the claim for hospitalization, clinics, and pharmacies, including national health insurance qualification data containing medical statements, disease codes, treatment codes, prescription details, and national health examination from 2002 to 2020. The disease codes in KNHIS are derived from the Korean Standard Classification of Disease, the 7th revision (KCD-7), modified from the International Classification of Disease, 10th revision (ICD-10). Additionally, the KNHIS dataset includes the NOE results of the NHS for individuals aged 19 and above. It is composed of a self-reported survey and oral examination by professional dentists. The NOE in Korea assesses various dimensions of oral health, including awareness of oral health, oral health habits, as well as the presence of dental caries and periodontal disease.

Study population

The study used the KNHIS-customized data with NHS data, which included adults from 2002 to 2020. The cohort comprised the data of 4,669,107 subjects between 2002 and 2003, confirmed by the end of 2020 (Fig. 1).

Fig. 1.

Flow chart of the study population

The baseline period of the study population was from 2002 to 2013, and individuals who underwent the NOE were tracked every two years until 2013.

Throughout the follow-up period from 2014 to 2020, we examined dental scaling, periodontal treatment, and dental caries treatment in the study cohort established during the baseline period. We included data on sex, age group, income, and type of city for the study population, based on demographic information from 2014.

The study included individuals who survived from 2002 to 2020. A total of 4,669,107 individuals were tracked, excluding 30,314 who died during the baseline period and 35,003 who died during the follow-up period. The study excluded the deceased and those subject to missing qualification from KNHIS during the total observation period.

National oral examination as an independent variable

The exposures during the baseline period: Individuals who underwent the NOE from 2002 to 2003 were tracked every two years until 2013. During this baseline period, they could receive a total of 6 NOE. Based on the number of the NOE, we classified the individuals into three groups: those who received 0–2 NOE (low), those who received 3–4 NOE (middle), and those who received 5–6 NOE (high). This categorization was designed to divide the data evenly across three groups for multinomial logistic regression analysis. In contrast, for the Poisson regression analysis, we did not group the scaling frequency, allowing the dependent variable to account for up to seven occurrences.

The outcomes during the follow-up period: Based on the NOE frequency classification from the baseline period, we examined individuals who underwent dental scaling procedures, periodontal treatment, and dental caries treatment from 2014 to 2020.

Dental scaling and treatments as dependent variables

The experience of receiving dental scaling and dental treatments can serve as outcome variables that operationally reflect oral health status.

The number of individuals who received dental scaling treatment code U2233 from 2014 to 2020 was investigated. Dental scaling, covered by insurance once a year starting from 2013, could be received 7 times by 2020. The dental scaling frequency was categorized as follows: 0–2 times (low), 3–5 times (middle), and 6–7 times (high).

We evaluated individuals who received treatment for periodontal disease and dental caries from 2014 to 2020. To investigate treatment experience data, it was important to ensure the validity of diagnoses more rigorously. For periodontal disease treatment, since diagnostic codes may appear even with a single occurrence, such as during annual full-mouth scaling, individuals who received periodontal disease-related diagnostic codes at least twice a year were defined as having received periodontal disease treatment. Therefore, it was defined by considering the presence of disease codes more than two times during the observation period: acute periodontitis (K052), chronic periodontitis (K053), periodontosis (K054), other periodontal diseases (K055), and unspecified periodontal disease (K056).

The treatment history for dental caries was defined by the presence of diagnostic codes occurring more than three times within the observation period. This threshold was selected to capture cases of ongoing or progressive dental caries that likely required treatment. These diagnostic codes for incipient or moderate dental caries included: dental caries limited to enamel (K020), dental caries extending into the dentin (K021), dental caries extending into pulp (K022), dental caries involving cementum (K023), dental caries involving both enamel and dentin (K024), dental caries involving both enamel and pulp (K025), dental caries involving both dentin and pulp (K026), dental caries involving enamel, dentin, and pulp (K027), other dental caries (K028), or dental caries, unspecified (K029).

Statistical analysis

The independent variables in this study were the frequency of the NOE, as well as sex, age group, income, and the type of city. The dependent variables were dental scaling, periodontal treatment, and dental caries treatment. The city was categorized as rural and metropolitan. Income was divided into five quintiles. The lowest income segment was the first quintile and defined as the lowest 20%. The highest income quintile was defined as the top 20%. The study also considered health insurance eligibility standards (head of household, family member, and medical aid beneficiaries).

The demographic characteristics of the study population are presented as counts (n) with percentages (%) for categorical variables. Descriptive statistics were analyzed using Chi-square tests. We conducted a multinomial logistic regression analysis to assess the impact of the extent of the NOE on the level of expert oral hygiene care (dental scaling; categorized as low (0–2 times), moderate (3–5 times), high (6–7 times)). The Poisson regression analysis was used to analyze the impact of the extent of the NOE on the frequency of oral hygiene care. β coefficients (natural logarithm values) were transformed back into rate ratios using the exponential function to facilitate an intuitive interpretation of the results of the Poisson regression model. All statistical analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC, USA).

Results

Table 1 shows 4,669,107 participants in study cohorts recruited in 2002 and 2003. When tracking a cohort group from 2002 to 2013, the distribution of individuals who received the NOE was 4,206,928 for low (0–2 times), 240,516 for middle (3–4 times), and 221,663 for high (5–6 times). A higher proportion of individuals in the group that underwent the NOE more frequently were male, in middle to older age groups (40-50 s), and had higher income levels (p < 0.001). Although a higher proportion of individuals across all three groups in the NOE received dental scaling at a low frequency, the group with higher in the NOE tended to receive dental scaling more frequently (p < 0.001). Regarding periodontitis treatment, the proportion of individuals undergoing treatment was higher among those with a high frequency of the NOE (p < 0.001).

Table 1.

Demographic factors of the study participants by frequency of oral examination

	Total subject		Oral examinationa (2002–2013)
	n	%	Low		Middle		High
			n	%	n	%	n	%
Total	4,669,107	100.00	4,206,928	90.1	240,516	5.15	221,663	4.75
Sex
Men	2,518,704	53.94	2,193,538	52.14	152,863	63.56	172,303	77.73
Women	2,150,403	46.06	2,013,390	47.86	87,653	36.44	49,360	22.27
Age group (2014)
30–39	963,332	20.63	898,522	21.36	31,718	13.19	33,092	14.93
40–49	1,298,364	27.81	1,141,467	27.13	70,780	29.43	86,117	38.85
50–59	1,207,175	25.85	1,062,853	25.26	72,170	30.01	72,152	32.55
60–69	702,299	15.04	631,791	15.02	46,329	19.26	24,179	10.91
70 +	497,937	10.66	472,295	11.23	19,519	8.12	6,123	2.76
Income (2014)
First	761,838	16.46	710,613	16.89	28,435	11.82	17,753	8.01
Second	784,605	16.95	719,318	17.10	34,099	14.18	26,383	11.90
Third	1,044,774	22.57	929,623	22.10	56,073	23.31	52,904	23.87
Fourth	945,861	20.44	830,130	19.73	53,755	22.35	56,040	25.28
Fifth	1,091,113	23.58	964,304	22.92	60,973	25.35	58,037	26.18
Type of city (2014)
Rural	3,086,842	66.11	2,795,120	66.44	152,415	63.37	139,307	62.85
Metropolitan	1,582,265	33.89	1,411,808	33.56	88,101	36.63	82,356	37.15
Scaling (2014–2020)
0 ~ 2	3,985,466	85.36	3,650,271	86.77	177,351	73.74	157,844	71.21
3 ~ 5	607,952	13.02	498,155	11.84	54,729	22.75	55,068	24.84
6,7	75,689	1.62	58,502	1.39	8,436	3.51	8,751	3.95
Periodontal disease treatment (2014–2020)
No	3,819,235	81.8	3,458,362	82.21	187,647	78.02	173,226	78.15
Yes	849,872	18.2	748,566	17.79	52,869	21.98	48,437	21.85
Incipient/moderate dental caries treatment (2014–2020)
No	4,442,244	95.14	4,003,075	95.15	228,087	94.83	211,082	95.23
Yes	226,863	4.86	203,853	4.85	12,429	5.17	10,581	4.77

^aOral examination: low; 0 ~ 2, middle; 3 ~ 4, high; 5 ~ 6

p < 0.001

Even after adjusting for sociodemographic variables in Table 2, significant differences in dental scaling by the NOE persisted, as indicated by the multinomial logistic regression model (p < 0.001). Higher NOE experience was associated with higher chances of receiving dental scaling than individuals with low-frequency NOE experience (Odds ratio (OR) = 2.30; 95% CI 2.28—2.32 for middle, OR = 2.48; 95% CI 2.45—2.50 for high). Throughout the follow-up period (step 2; 2014–2020), the subgroup consistently undergoing dental scaling 6–7 times demonstrated the highest adjusted odds ratio (OR = 3.30; 95% CI 3.22—3.38) within the high-frequency NOE group, in contrast to other groups. Individuals who were females, aged 30–39, high-income, and metropolitan residents had the highest adjusted OR in the 3 to 5 dental scaling than their counterparts. In the group receiving scaling 6–7 times, higher adjusted ORs were observed among females, individuals in their 50 s, those with higher incomes, and metropolitan residents. As shown in Table 3, the middle group of the NOE received dental scaling 1.69 times more frequently than the low group, according to the Poisson regression analysis, after adjusting for confounding variables (p < 0.001). Similarly, the group consistently undergoing the NOE received dental scaling 1.77 times more frequently than the low-frequency group.

Table 2.

Multinomial logistic regression models for frequency of oral examination^a (2002–2013) and dental scaling (2014–2020)

	3–5 times of dental scaling						6–7 times of dental scaling
	Crude analysis			Adjusted analysisb			Crude analysis			Adjusted analysisb
	OR	95% CI		OR	95% CI		OR	95% CI		OR	95% CI
		LL	UL		LL	UL		LL	UL		LL	UL
Oral examination
Low	(ref)	-		(ref)	-		(ref)	-		(ref)	-
Middle	2.261	2.239	2.284	2.300	2.276	2.324	2.968	2.900	3.038	2.910	2.841	2.980
High	2.556	2.531	2.582	2.475	2.449	2.501	3.459	3.381	3.540	3.295	3.217	3.375
Sex
Men	(ref)	-		(ref)	-		(ref)	-		(ref)	-
Women	1.178	1.171	1.184	1.336	1.328	1.343	1.161	1.144	1.178	1.376	1.355	1.396
Age group
30–39	(ref)	-		(ref)	-		(ref)	-		(ref)	-
40–49	0.984	0.977	0.992	0.938	0.931	0.946	1.242	1.216	1.269	1.165	1.139	1.191
50–59	1.036	1.028	1.043	0.910	0.903	0.917	1.453	1.423	1.485	1.202	1.176	1.228
60–69	0.828	0.821	0.836	0.737	0.730	0.744	1.287	1.256	1.319	1.082	1.055	1.109
70 +	0.285	0.281	0.289	0.268	0.264	0.272	0.390	0.374	0.405	0.357	0.343	0.372
Income
First	(ref)	-		(ref)	-		(ref)	-		(ref)	-
Second	1.117	1.106	1.129	1.076	1.065	1.087	1.129	1.095	1.164	1.082	1.049	1.115
Third	1.266	1.254	1.278	1.205	1.193	1.217	1.366	1.328	1.404	1.257	1.223	1.292
Fourth	1.476	1.462	1.490	1.411	1.397	1.424	1.704	1.659	1.751	1.547	1.506	1.590
Fifth	1.887	1.870	1.905	1.873	1.856	1.890	2.573	2.509	2.639	2.407	2.347	2.469
Type of city
Rural	(ref)	-		(ref)	-		(ref)	-		(ref)	-
Metropolitan	1.166	1.159	1.172	1.133	1.126	1.139	1.357	1.337	1.377	1.280	1.261	1.299

^aOral examination: low; 0 ~ 2, middle; 3 ~ 4, high; 5 ~ 6

^bAdjusted for sex, age group, income, and city

p < 0.001

Table 3.

Association between oral examination (2002–2013) and dental scaling (2014–2020) by Poisson regression

	Crude analysis			Adjusted analysisb
	Rate ratio	95% CI		Rate ratio	95% CI
		LL	UL		LL	UL
Oral examinationa
Low	(ref)	-		(ref)	-
Middle	1.629	1.624	1.635	1.691	1.685	1.697
High	1.780	1.774	1.786	1.766	1.760	1.772
Sex
Men	(ref)	-		(ref)	-
Women	1.117	1.115	1.119	1.214	1.211	1.216
Age group
30–39	(ref)	-		(ref)	-
40–49	1.119	1.117	1.122	0.944	0.942	0.947
50–59	1.142	1.140	1.144	0.911	0.908	0.913
60–69	0.922	0.920	0.925	0.780	0.777	0.782
70 +	0.383	0.381	0.384	0.357	0.355	0.358
Income
First	(ref)	-		(ref)	-
Second	0.769	0.767	0.771	0.662	0.660	0.664
Third	0.850	0.848	0.852	0.701	0.699	0.703
Fourth	0.933	0.931	0.935	0.757	0.755	0.759
Fifth	1.059	1.057	1.061	0.839	0.837	0.841
Type of city
Rural	(ref)	-		(ref)	-
Metropolitan	1.113	1.111	1.116	1.092	1.090	1.094

^aOral examination: low; 0 ~ 2, middle; 3 ~ 4, high; 5 ~ 6

^bAdjusted for sex, age group, income, and city

p < 0.001

Table 4 shows an association between oral disease treatment and the NOE, as analyzed through logistic regression (p < 0.001). Middle and high groups were 1.23 times more likely to receive periodontal disease treatment than the low group in the NOE. Additionally, the middle group received 1.08 times more Incipient/moderate dental caries treatment than the low-frequency group in the NOE.

Table 4.

Logistic regression models for oral health treatment (2014–2020) by frequency of oral examination^a

	Periodontal disease treatment								Incipient/moderate dental caries treatment
	Crude analysis			p-value	Adjusted analysisb			p-value	Crude analysis			p-value	Adjusted analysisb			p-value
	OR	95% CI			OR	95% CI			OR	95% CI			OR	95% CI
		LL	UL			LL	UL			LL	UL			LL	UL
Oral examination (2002–2013)
Low	(ref)	-			(ref)	-			(ref)	-			(ref)	-
Middle	1.302	1289	1.315	< 0.001	1.226	1.214	1.239	< 0.001	1.070	1.050	1.090	< 0.001	1.079	1.058	1.099	< 0.001
High	1.292	1.279	1.305	< 0.001	1.229	1.216	1.243	< 0.001	0.984	0.965	1.004	0.123	1.020	0.999	1.041	0.062
Sex
Men	(ref)	-			(ref)	-			(ref)	-			(ref)	-
Women	0.962	0.957	0.966	< 0.001	0.972	0.967	0.977	< 0.001	1.133	1.124	1.143	< 0.001	1.134	1.124	1.143	< 0.001
Age group
30–39	(ref)	-			(ref)	-			(ref)	-			(ref)	-
40–49	1.387	1.376	1.397	< 0.001	1.365	1.355	1.375	< 0.001	1.242	1.216	1.269	< 0.001	0.840	0.830	0.850	< 0.001
50–59	1.760	1.747	1.773	< 0.001	1.710	1.697	1.723	< 0.001	1.453	1.423	1.485	< 0.001	0.941	0.929	0.953	< 0.001
60–69	1.832	1.817	1.847	< 0.001	1.791	1.777	1.806	< 0.001	1.287	1.256	1.319	< 0.001	1.091	1.076	1.106	< 0.001
70 +	1.312	1.300	1.325	< 0.001	1.307	1.295	1.320	< 0.001	0.390	0.374	0.405	< 0.001	0.921	0.907	0.936	< 0.001
Income
First	(ref)	-			(ref)	-			(ref)	-			(ref)	-
Second	1.057	1.048	1.066	< 0.001	1.050	1.041	1.059	< 0.001	0.977	0.963	0.992	< 0.050	0.992	0.977	1.007	0.296
Third	1.118	1.109	1.127	< 0.001	1.081	1.072	1.089	< 0.001	0.997	0.983	1.011	0.677	1.023	1.008	1.037	< 0.050
Fourth	1.188	1.178	1.197	< 0.001	1.124	1.114	1.133	< 0.001	1.028	1.013	1.043	< 0.001	1.050	1.035	1.065	< 0.001
Fifth	1.258	1.248	1.268	< 0.001	1.177	1.167	1.186	< 0.001	1.098	1.083	1.113	< 0.001	1.093	1.078	1.108	< 0.001
Type of city
Rural	(ref)	-			(ref)	-			(ref)	-			(ref)	-
Metropolitan	1.076	1.071	1.081	< 0.001	1.047	1.042	1.053	< 0.001	1.100	1.090	1.109	< 0.001	1.093	1.083	1.102	< 0.001

The year in parentheses denotes the observation year

^aOral examination: low; 0 ~ 2, middle; 3 ~ 4, high; 5 ~ 6

^bAdjusted for sex, age group, income, and city

Discussion

This study examined the effect of the NOE on dental scaling and oral health treatments. The discrepancy in the frequency of dental scaling was more pronounced among individuals with irregular participation in the NOE. Conversely, those who consistently engaged in the NOE exhibited a greater propensity to undergo preventive dental scaling than their counterparts who showed inconsistent participation. Furthermore, there was a higher rate of proactive periodontal treatment among individuals who consistently participated in the NOE than those who showed irregular participation. Disparities based on sex, age, and income were notably higher in the group of people within the high frequency of the NOE. Those who consistently received scaling were females, individuals in middle-age groups, and those with higher incomes. Dental treatment was associated with higher income and urban residency.

Health behavior is a pivotal factor influencing health outcomes and morbidity and mortality rates, particularly in the prevalence of chronic or lifestyle-related diseases [20–22]. Enhancing health behaviors is more cost-effective in reducing disease morbidity and mortality than improving social and physical environments or healthcare systems for health promotion [23]. The NHS offers opportunities for early detection of chronic diseases and physical ailments, prompting individuals to adopt regular health behaviors, healthy dietary habits, and routine medical check-ups and treatments [24, 25]. From these perspectives, the NHS programs were considered cost-effective for patients [26–28]. Previous studies show that health screening programs reduce the mortality rate of oral cancer in high-risk individuals [29, 30].

We found that the regular participants of the NOE were more inclined to receive dental scaling in this study, which is consistent with the findings of a previous study that indicated a higher likelihood of dental scaling among participants in the NHS in Korea [31]. Our research stands out due to its longitudinal design, a departure from previous studies. By evaluating the frequency of the NOE at the baseline period and assessing the number of dental scaling procedures during the follow-up period, we could confirm its causal impact. This methodology represents a notable strength of our study.

Furthermore, we observed a significant relationship between the frequency of the NOE and periodontal treatment. A previous study indicated that health screening leads to subsequent inpatient and outpatient medical treatments following the screening examination [32]. Although those who regularly participated in the NOE tended to receive more treatments in this study, it is likely due to the early detection of oral diseases through the NOE, which led to an increase in treatments. While this may initially appear to increase oral health care costs in the short term, it suggests that long-term expenses associated with oral health care and maintenance may ultimately decrease [33–35]. Individuals can effectively manage their oral health status and benefit from continuous and long-term preventive effects through the NOE. Sustained long-term prevention effects and early treatments contribute to an overall improvement in public health, potentially reducing socioeconomic disease burden, thus allowing for cost-effective and efficient utilization of resources [16]. Hence, it is crucial to develop strategies to enhance the participation rate and effectiveness of the NOE, considering their social value and economic efficacy. NOE in Korea includes a questionnaire and visual inspection to provide information on dental caries, periodontal disease, brushing habits, and the need for scaling. Incorporating additional diagnostic tools, such as panoramic radiographs, could enhance the effectiveness of the NOE program and potentially help increase participation rates [36]. Furthermore, if the screening process is not limited to just diagnostics but is followed by a referral to a primary care provider for treatment, the effectiveness of the NOE program would be further enhanced [37].

This study showed demographic differences in dental scaling and dental treatment. Individuals who consistently received dental scaling were more likely to be female, middle-aged, and have higher incomes. In the previous study, women demonstrated more positive attitudes toward dental visits and better oral health behaviors than men [38]. Previous research in Korea also indicates that socioeconomic disparities influence the utilization rates of dental scaling [39]. Dental treatment was associated with higher income and urban residency. Prior studies show that the disparities in unmet demand for dental health care were associated with income levels and geographical factors [40, 41]. These results are consistent with findings from previous studies. Considering the epidemiological characteristics of the NOE, it would be beneficial to prioritize the provision of mobile NOE services at senior welfare centers and nursing homes, along with the NOE coverage benefits, to vulnerable populations, in order to encourage their participation. By promoting NOE participation, timely preventive and therapeutic interventions can be facilitated, overall oral health can be improved, and the gap in unmet oral health care needs can be reduced [42]. In the long term, this could also lower national welfare expenditures.

This study has several limitations. First, we could not assess health factors, behavior factors, and accessibility to healthcare and occupation, potentially influencing the participation rate in national oral health examinations. While our study analyzed sociodemographic factors identified as relevant in previous research, careful interpretation considering unmeasured confounding factors is necessary. Second, non-covered data not included in the National Health Insurance Service database were not accounted for. However, under the NHIS, scaling is covered for all individuals aged 19 and older once a year, making it uncommon for this procedure to be performed as a non-covered service. Periodontal disease treatment and incipient/moderate dental caries treatment are covered by insurance without any restrictions on frequency. Finally, our analysis relied on data from the NHIS, which may have been affected by policy changes in insurance coverage related to oral health diseases, which might have affected dental care utilization.

Conclusions

This study shows the effect of NOE on dental scaling and oral health treatments among South Korean adults during the baseline periods from 2002 to 2013 and the follow-up period from 2014 to 2020. Those who regularly underwent the NOE were more likely to receive dental scaling, periodontal treatment, and incipient/moderate dental caries treatment. In the high-frequency NOE group, significant disparities based on sex, age, and income were notably higher. These results can serve as foundational evidence for future research and policy development on the NOE program.

Abbreviations

NHS

National Health Screening

NOE

National Oral Examination

KNHIS

Korean National Health Insurance Service

Authors’ contributions

Conceptualization: HG. Data curation: HG and YHC. Formal analysis: HG. Funding acquisition: YHC. Methodology: HG. Project administration: YHC. Visualization: HG and YHC. Writing – original draft: HG. Writing – review & editing: HG, MK, and YHC.

Funding

This work was supported by the Korea Health Industry Development Institute (KHIDI) grant funded by the Korean government (HI19C1218), and the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (RS-2024-00349360).

Data availability

The data used in this study were obtained from the NHIS National Cohort, it can only be disclosed to the people who had authorized by NHIS. For obtaining the NHIS National Sampling Cohort, go to the following web site, and submit the application form (https://nhiss.nhis.or.kr/bd/ab/bdaba021eng.do). The committee will evaluate that, and notice the determination of deliberation within 25 days from the data of application. And then, applicants who passed deliberation can use this data after payment of fee.

Declarations

Ethics approval and consent to participate

This study complied with the Declaration of Helsinki, and the study protocol was approved by the Kyungpook National University Institutional Review Board (KNU-2021–0489), and the National Evidence-based Healthcare Collaborating Agency (NECAIRB21-009). Informed consent was waived since this is a retrospective study of de-identified administrative data.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.