1.Backgroud

According to the frequent disease statistics of Healthcare Bigdata Hub, 17.4 million patients received outpatient treatment for gingivitis and periodontal disease (K05) in 2021, ranking first as the most frequent outpatient disease. The number of patients with gingivitis and periodontal disease has more than doubled compared to the number of patients with 8.03 million in 2011 (the second most frequent outpatient disease). The number of dental caries (K02) patients is 6.35 million (4th frequent outpatient disease) in 2021 compared to 5.42 million (7th frequent outpatient disease) in 2011, and has been also maintained as a frequent disease for a long time¹⁾. The main causes of periodontal disease are bacterial plaque and tartar, which are formed by the adhesion and proliferation of oral bacteria on the tooth surface. Nutritional status, drugs, immunity, endocrine system, and systemic diseases can also cause inflammatory lesions in the gingival tissues. Prolonged inflammation is the cause of tooth loss by inducing deep periodontal pocket formation, gingival recession, and destruction of periodontal ligaments and alveolar bone. Since plaque deposition on tooth surface is a major cause of the progression of gingivitis and periodontitis, control of the amount of plaque on tooth surface closely affects the health status of the gingiva. Therefore, it is important to clearly identify relevant risk factors, and continuous oral hygiene management is required to control the dental plaque for periodontal disease prevention.

According to the previous report, 93.9% of Seoul citizens brush their teeth as an oral health practice, but the use of auxiliary oral hygiene products except toothpicks is very low²⁾. Toothbrush is the most important product in oral hygiene management, but dental floss, interdental toothbrush, mouthwash, and tongue cleaner are also widely used as oral hygiene products. Toothbrushing reduced the incidence of interdental papillitis by 6.6%, but the incidence was significantly reduced to 26.3% when interdental cleaning using rubber cones was used along with brushing³⁾. Therefore, interdental cleaning is an effective oral hygiene practice that can prevent the transition to gingivitis or periodontitis. Interdental plaque, which is difficult to remove with toothbrushing, can be effectively helped with dental floss or an interdental toothbrush. The use of dental floss not only reduced gingivitis in the interdental area, but also prevented dental caries on the adjacent tooth surface, and showed the effect of removing halitosis according to interdental cleaning⁴⁾. It was found that 80% of the dental plaque in the interdental area was removed by flossing⁵⁾. Compared to the toothbrush alone or the toothbrush and dental floss, the combined use of the toothbrush and interdental toothbrush exhibited an 89-96% plaque removal effect⁶⁾.

2.Objectives

As various types of dental floss are commercially available, they are selected according to individual preferences and used for oral hygiene. Dental floss using thread type is mainly taught, but the introduction of floss using other types of floss is very insufficient. Therefore, in this study, after using Y-type and C-type dental floss along with thread-type dental floss, the need for various types of floss education was derived by examining the floss preference according to the type. In addition, the change in future intention to use dental floss after flossing experience among non-users was investigated according to gender, age, education level, and occupational status.

1.Ethic statement

The present study was approved by the Institutional Review Board of Eulji University (IRB No. EU19-70). Informed consent was obtained from participants.

2.Study design

This study used a descriptive research design aimed to identify the floss preference by types and future use intention according to floss experience through a cross-sectional survey. This study was described in accordance with the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines (https://www.strobe-statement.org).

3.Subjects

This study is an individual interview survey for the general public living in Seoul and Gyeonggido from Jan. 1 to Mar. 30, 2019. After explaining the purpose of the study, only subjects who voluntarily agreed to the questionnaire participated in the study. In the case of the elderly, questionnaires and experiments were conducted by visiting the elderly home and security office. Students of the same major from Eulji University to which the author belongs were excluded from the participants. A total of 453 people responded, of which 419 responses were applied to the final analysis, excluding missing values of major variables and 34 respondents under the age of 20 years. The sample size was calculated using G*Power sampling software (version 3.1.9.7 for Windows). The minimum required sample size was estimated to be 220 persons with an a error of 5%, power of 95%, degree of freedom of 5 and medium effect size of 0.3 by applying the chi-squared test as the main analysis method. Additional samples were collected in each group to compensate for processing errors.

4.Materials

The questionnaire consisted of general characteristic questions of the participants and questions related to before and after using dental floss. Three types of dental floss were used for this study: tread type floss (Oral-B waxed floss; P&G, New York, NY, USA), Y-type floss (Daiso, Seoul, Korea), and C-type floss (Oral-B; P&G) (Fig. 1). Subjects answered the questionnaire after directly using dental floss by type. The preference for each type of floss was investigated by dividing it into anterior and posterior regions.

Fig. 1. Types of dental floss. (A) Thread type floss. (B) Y-type floss. (C) C-type floss.

5.Data analysis

The collected data were analyzed using SPSS 28.0.1.1 (IBM Corp., Armonk, NY, USA) statistical program. In consideration of the frequency of the survey subjects, the age groups were divided into 20s (20∼29 y), middle-aged (30∼64 y), and the elderly (65 y and older). Educational level was divided into high school graduation and below and college graduation and above. In order to classify only the degree of occupation, three groups were analyzed: students, office workers, and other groups that did not respond. The general characteristics of the subjects were analyzed according to whether or not dental floss was used, the frequency of floss use and the type of floss being used for floss users, and the reasons for not using floss for non-floss users were investigated. In addition, the preference and future intention to use dental floss after using three types of dental floss were surveyed for all respondents. All statistics were expressed as frequencies and percentages for categorical variables, and the chi-squared test was used to determine the statistical significance of associations between the variables. A p-value ≤0.05 was considered statistically significant.

In this study, 53.5% of the total respondents were female. Among the participants, 49.6% were in their 20s, 26% were middle-aged and elderly (30∼64 y), and 24.3% were 65 years or older. The educational level of the respondents was high school graduate or lower (63.0%), and college graduate or higher (37.0%). The occupations of the respondents were 99 students (23.6%) and 156 office workers (37.2%). Other groups, including those who did not provide information on occupations and other respondents excluding students and office workers, accounted for 39.1%. Of the total 419 respondents, 158 (37.7%) floss users and 261 (62.3%) non-floss users. The proportion of female is 43.3% of floss users and 56.7% of non-floss users. The proportion of floss users is 31.3% of male and 43.3% of female. Among the elderly over 65, the number of floss users is 29.4% and the non-users are 70.6%, which is relatively high among the elderly. In addition, among those who graduated from college or higher, 47.7% of floss users and 52.3% of those who did not use dental floss. The use of dental floss by employed group was relatively high than that of other occupations (42.9%) (Table 1).

Table 1

Descriptive Statistics of General Characteristics according to Use of Dental Floss

Variable	Total (n=419)	Use of dental floss		p-valuea
		User (n=158)	Non-user (n=261)
Sex				0.011
Male	195 (46.5)	61 (31.3)	134 (68.7)
Female	224 (53.5)	97 (43.3)	127 (56.7)
Age group (y)				<0.001
20∼29	208 (49.6)	70 (33.7)	138 (66.3)
30∼64	109 (26.0)	58 (53.2)	51 (46.8)
≥65	102 (24.3)	30 (29.4)	72 (70.6)
Education				0.001
High school graduate or less (≤12 y)	264 (63.0)	84 (31.8)	180 (68.2)
College or more (≤13 y)	155 (37.0)	74 (47.7)	81 (52.3)
Job status				0.234
Students (unemployed)	99 (23.6)	34 (34.3)	65 (65.7)
Employed (waged)	156 (37.2)	67 (42.9)	89 (57.1)
Etc. or missing	164 (39.1)	57 (34.8)	107 (65.2)

All values are presented as number (%) for categorical variables.

^aAssociations with the use of dental floss were estimated by chi-squared test and percentages are expressed in rows to be 100%.

The frequency of flossing and the type of dental floss used by 158 floss users were analyzed (Table 2). Once a week is the highest with 53.2%, and daily users are 22.2%. As for the types of dental floss used, tread type is 67.1%, C-type floss is 25.3%, and Y-type floss is 6.3%. The reasons for not using dental floss among 261 non-users were ‘don’t know how to use’ 95 (36.4%), ‘it's tiresome’ 78 (29.9%), ‘inconvenient to use’ 46 (17.6%), and ‘not aware of the need to use’ was followed by 33 participants (12.6%) (Table 3).

Table 2

Utilization Status of Dental Floss among Users

Variable	User (n=158)
Frequency of flossing
Daily	35 (22.2)
2 or 3 times/week	39 (24.7)
Once/week	84 (53.2)
Floss type
Thread type	106 (67.1)
C-type	40 (25.3)
Y-type	10 (6.3)
Etc.	2 (1.3)

All values are presented as number (%) for categorical variables.

Table 3

The Main Reasons for not Using Dental Floss among Non-Users

Variable	Non-user (n=261)
Main reason not to use
Don’t know how to use	33 (12.6)
It’s tiresome	78 (29.9)
Inconvenient to use	46 (17.6)
Not aware of the need to use	95 (36.4)
Etc.	9 (3.4)

All values are presented as number (%) for categorical variables.

Regardless of whether or not floss was used, all participants answered their preference after using 3 types of floss to the anterior and posterior region (Table 4). As a result, both floss users and non-users had the highest preference for the C-type floss. In addition, the preference of the C-type floss was the highest for both the anterior and posterior regions. In the case of the anterior region, the preference for C- type floss users was the highest at 46.8%, followed by thread type 37.3% and Y-type 15.8%. In the case of the posterior region, the preference for C-type floss users was the highest at 41.1%, followed by Y-type 31.6% and thread type 27.2%. Among non-users of dental floss, preference for C-shape was highest in the anterior region at 55.6%, followed by Y-type 23.8% and thread type 20.7%. Among non-users of dental floss, preference for C-shape was the highest in the posterior region at 44.1%, followed by Y-type 34.9% and thread type 21.1%. In the anterior region, there was a statistically significant association between the use of floss and the floss type (p=0.001), but it was not statistically significant in the posterior region (p=0.352).

Table 4

Preference for Dental Floss Type according to Application Area for All Respondents

Variable	Application area
	Anterior			Posterior
	n (%)	p-valuea		n (%)	p-valuea
User (n=158)		0.001			0.352
Thread type	59 (37.3)			43 (27.2)
C-type	74 (46.8)			65 (41.1)
Y-type	25 (15.8)			50 (31.6)
Non-user (n=261)
Thread type	54 (20.7)			55 (21.1)
C-type	145 (55.6)			115 (44.1)
Y-type	62 (23.8)			91 (34.9)

All values are presented as n (%) for categorical variables.

^aAssociations between floss use and floss type were estimated by chi-squared test for each application area.

After all tests were completed, the intention to use dental floss in the future was investigated among 261 non-users of floss (Table 5). Of the 261 non-floss users, 137 participants (52.5%) answered positive intention to use dental floss in the future, and 124 participants (47.5%) answered negative intention to use dental floss in the future. Female’s positive future intention to use dental floss was 54.3%, which was slightly higher than the negative future intention to use dental floss (45.7%), but the association between gender and future intention to use dental floss was not statistically significant (p=0.562). Among the middle-aged (30∼64 y) about their intention to use dental floss in the future, the positive response was 35 (68.6%), which was twice as high as the negative response 16 (31.4%). On the other hand, 28 (38.9%) positive responses to the intention to use dental floss in the future over 65 years of age were significantly lower than 44 (61.1%) negative responses. After the floss application experience, the positive future floss intention of non-users was statistically significantly associated with age (p=0.005). The positive intention to use dental floss in the future of non-users with education below high school was 89 (49.4%), similar to the negative response of 91 (50.6%). In addition, the positive intention to use dental floss among non-users with college graduation or higher education was 48 (59.3%) higher than the negative 33 (40.7%), but the correlation between the future intention to use dental floss and education level was not statistically significant (p=0.142).

Table 5

Willingness to Use Dental Floss in the Future among Non-Users (n=261)

Variable	Willingness to use dental floss
	Yes (n=137)	No (n=124)	p-valuea
Sex			0.562
Male	68 (50.7)	66 (49.3)
Female	69 (54.3)	58 (45.7)
Age group (y)			0.005
20∼29	74 (53.6)	64 (46.4)
30∼64	35 (68.6)	16 (31.4)
≥65	28 (38.9)	44 (61.1)
Education			0.142
High school graduate or less (≤12 y)	89 (49.4)	91 (50.6)
College or more (≤13 y)	48 (59.3)	33 (40.7)

All values are presented as n (%) for categorical variables and expressed as a percentage of rows.

^aAssociations with the willingness to use dental floss were estimated by chi-squared test.

1.Interpretation

Dental caries, gingivitis, and periodontitis are oral diseases with very high prevalence, and several factors are related. Plaque growth due to glycoproteins in the bacterial membrane attached to the tooth surface is a major local risk factor. Bacteria in dental plaque secrete acids that cause tooth decay and toxins that irritate gingival cells. Accumulated plaque hardens into tartar, which is difficult to remove with general toothbrushing and causes gum disease such as periodontal inflammation. Therefore, dental plaque management is very important to prevent various oral diseases. The dental plaque remaining that cannot be removed by toothbrushing aggregates with the calcium component of saliva and is converted into calculus, which is more difficult to remove. Increased subgingival calculus not only induces periodontitis, but also reduces the adhesion between the root and alveolar bone, leading to tooth loss. For effective dental plaque management, floss and interdental toothbrushes are very effective in addition to general toothbrushing.

2.Comparison with previous studies

Dental plaque removal was not performed properly in about 40% of the total tooth surface in the oral cavity⁷⁾. Plaque removal was insufficient from the molars rather than the anterior teeth, and the removal of plaque from the lingual and proximal surfaces rather than the buccal surfaces was also insufficient^8,9). These areas show a high correlation with the areas most prone to gingivitis and periodontitis¹⁰⁾. Oral hygiene management for the control of proximal, lingual, and posterior plaques that are difficult to reach by brushing should be more actively implemented. Only toothbrushing cleans about 60% of the dental plaque¹¹⁾, but when using dental floss together, 80% of the interdental plaque is removed¹²⁾. However, according to the Korea Oral Health and Brushing Habit Survey, published by the Korean Society of Preventive Dentistry in 2017, only 29.1% of the respondents answered that they properly brushed between their gums and teeth¹³⁾. In addition, according to the 2016 Korean Dental Medical Yearbook, the results of a survey on the use of oral supplements for those aged 19 and over showed that the users of toothbrushing, floss, interdental brushes, and gargling solutions were about 20%, which was not different from the results of the 2012 survey (about 18.5%)¹⁴⁾. Therefore, awareness of problems in oral health management and more active oral hygiene education are needed. It is also necessary to identify the type of oral hygiene product that an individual prefers and to prepare an appropriate method for using it.

As a result of this study with 419 participants, 37.7% of floss users and 62.3% of non-floss users. The percentage of non-floss users was significantly higher. Of the 419 participants, 53.2% of floss users floss once a week, but only 22.2% daily. The American Dental Association (ADA) recommends removing interdental plaque at least once a day for oral hygiene. Reasons for not using dental floss were in the following order: unaware of necessity (36.4%), annoyance (29.9%), and inconvenient use (17.6%). Surprisingly, 67.1% of floss users used thread type, 25.3% for C-type, and 6.3% for Y-type. However, after experiencing all three types of floss, the floss user's floss preference was shifted to C-type. The preference for using C-type dental floss was high in both the anterior and the posterior region. Dental floss users preferred thread type floss (37.3%) in the order of C-type (46.8%) in the anterior region, and Y-type floss (31.6%) in the posterior region was also high. Even non-floss users preferred C-type floss very highly after experiencing all three types of floss, and the preference to use C-type floss was also high in both the anterior and posterior regions. These results suggest that various types of dental floss education are needed according to individual preferences and tooth shapes.

Discomfort in flossing is a major cause of hindrance to regular flossing despite the fact that floss users are aware of the importance of flossing. As a result of examining the intention of non-users to use dental floss in the future, it was found that those in their 20s (53.6%) and those in their 30∼64 years of age (68.6%) had high positive intentions after flossing application. However, non-users over the age of 65 had a negative intention to use dental floss in the future even after flossing application (61.1%). And 31∼47% of non-floss users in their 20s and 30∼64 years of age remain unwilling to floss in the future even after flossing application. In addition, the intention to use dental floss of the elderly 65 years and older, which has a very high prevalence of periodontal disease, remains negative even after flossing application (61.6%). Although there is a significant statistical relationship between the intention to use dental floss in the future and age, it is necessary to educate and practice the importance of dental floss for continuous oral hygiene management.

3.Limitation

The proper use of toothbrushing, mouthwash, or other related hygiene tools is effective in managing and main-taining cleanliness of the dental and interdental biofilms. Mouthwash is effective for hygiene management in areas that tools cannot reach. Although it has been reported that the effect of dental floss is very limited in terms of improving oral hygiene¹⁵⁾, this means that since dental floss cannot completely solve interdental hygiene, it should be applied as a supplementary hygiene management tool rather than dental floss alone. However, research results have been consistently reported that flossing is very effective in reducing periodontal disease and dental caries¹⁶⁾. In particular, in the case of a dense tooth structure due to a limited space between teeth or a mismatch between the tooth size and the jaw size, the use of dental floss may be more effective. Therefore, oral hygiene education and dental floss selection taking into account the structure of individual teeth are necessary, and continuous motivation of dental professionals to help with oral health behavior will be required. Compared to those in their 20s, the participation rate in this study for other age groups is relatively low. Therefore, there is a limit to deriving research results that evenly reflect the opinions of each age group. In addition, since dental caries and periodontal disease of the participants were not investigated, there is a limit to ascertaining the relationship between dental caries and periodontal disease according to the use of dental floss.

4.Conclusions

In this study, the preference for floss by various types was investigated, and through this, the necessity of dental floss education according to the floss type was suggested. In addition, oral hygiene education and flossing practice by oral health professionals are required to encourage continuous floss use.

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2022R1F1A1063204).

No potential conflict of interest relevant to this article was reported.

Human experiment was approved by the Institutional Review Board (IRB) of Eulji University (approval No. EU19-70).

Conceptualization: Myoung-Hee Kim, Hae Yeon Yun, and Young Sun Hwang. Data acquisition: Myoung-Hee Kim, Hae Yeon Yun, and Young Sun Hwang. Formal analysis: Myoung-Hee Kim, Hae Yeon Yun, Ji Hyeon Park, and Young Sun Hwang. Funding: Young Sun Hwang. Supervision: Myoung-Hee Kim, Hae Yeon Yun, Ji Hyeon Park, and Young Sun Hwang. Writing—original draft: Myoung-Hee Kim, Hae Yeon Yun, and Young Sun Hwang. Writing—review & editing: Myoung-Hee Kim and Young Sun Hwang.

The data and materials of this article are included within the article. The data supporting the findings of this study are available from the corresponding author upon reasonable request.