1.Background

Oral diseases are caused by oral factors and various systemic diseases^1,2). According to the 2023 frequent disease statistics in Korea provided by the Health Insurance Review and Assessment Service, the number of outpatients with gingivitis and periodontal disease (code K05) was the highest (18,836,481), and dental caries (code K02) was the sixth most common oral problem (6,268,887)³⁾. Though periodontal disease and dental caries may be caused by various factors and diseases, the fundamental cause is dental plaque. Dental caries are caused by mineral loss of the tooth surface due to dental plaque, and inflammation of the periodontal tissues around the plaque leads to gingivitis and periodontitis^4,5). Therefore, to prevent and suppress the progression of these two diseases, regular management of oral hygiene and dental check-ups are necessary. Maintenance of proper tooth brushing habits is also needed. Various oral care products are used to maintain oral health, but tooth brushing is the most effective method for mechanically removing dental plaque. Brushing removes dental plaque and food debris that cause bacterial growth and polishes the teeth. The massaging effect of brushing also improves blood circulation, helping to reduce inflammation in periodontal tissues and promoting gum health⁶⁾. However, it is essential to select a toothbrush that suits the individual’s dental and periodontal condition, tooth alignment, and occlusal state. As interest in oral health rises, a diverse range of functional toothbrushes have been introduced alongside standard toothbrushes. Electric toothbrushes, interdental brushes, sonic toothbrushes, functional toothbrush heads, and toothbrushes for infants and children contribute to maintaining a higher level of oral hygiene than that achieved with regular toothbrushes. Education on proper oral care and brushing is also necessary for maintaining oral health. Improper toothbrush care can increase the risk of microbial growth and infection, so choosing a toothbrush that is easy to clean and maintaining hygienic practices after use are crucial.

2.Objectives

Recently, the user base for large-head toothbrushes, featuring bristles approximately 4 cm in length, has expanded due to their easy availability in supermarkets and online shopping malls. In contrast, the bristles of a standard toothbrush are about 2 cm long. Large-head toothbrushes are favored over regular toothbrushes because they offer the advantage of efficiently brushing 4 to 5 teeth simultaneously. According to the June 2022 toothbrush brand big data analysis conducted by the Korean Corporate Reputation Research Institute of Korea Media Marketing Co., Ltd., the large-head toothbrush ranked second (brand reputation index 595.201), showing a 57.77% increase compared to the previous month’s brand reputation index of 377,251, indicating high interest⁷⁾. On the online shopping mall Coupang, it also has a total user rating of 4.9 out of 5, with over 100,000 reviews, indicating high satisfaction⁸⁾. Considering the importance of plaque removal and hygiene management, an evaluation of large-head toothbrushes is necessary. Since toothbrushes are frequently used, proper cleaning and storage are crucial. Incorrect cleaning and storage can promote bacterial growth and cause oral infections. Surfactants in toothpaste have a cleansing effect on the mouth but can also cause oral mucosal inflammation, taste changes, and dry mouth⁹⁾. Given that toothbrushes are the most effective and frequently used tool for oral hygiene, attention to cleaning and storing toothbrush bristles is essential.

There have been studies on the degree of microbial contamination of toothbrushes based on storage methods and the appropriate temperature for toothbrush cleaning, but these results are limited to standard toothbrushes¹⁰⁾. Additionally, reports exist on the amount of toothpaste used and the time required for brushing based on the shape of the toothbrush head, but the effectiveness of plaque removal and the effect on hygiene management based on the size of the toothbrush head has not been determined^11,12). This study aimed to evaluate the effectiveness of plaque removal using large-head toothbrushes, which have gained high consumer interest and satisfaction, and compare these results with those of regular-sized toothbrushes. Based on this data, we aim to provide key points to help consumers make informed choices when selecting a toothbrush.

1.Study participants

Fifteen adults in their 20s, who had more than 28 teeth and who had not received dental scaling within the 4 months prior to the experiment or had any orthodontic appliances, participated in the study. They participated in two experiment sessions, with a 1-week interval between. Participants were instructed not to perform any oral hygiene activities, such as brushing or using mouthwash, after eating 2 hours before the experiment. All subjects voluntarily participated in the study after providing written informed consent. The present study was approved by the Institutional Review Board of Eulji University.

2.Methods

1) Research tools

Regular-sized toothbrushes with a brush head size of approximately 2 cm (Aekyung, Seoul, Korea) and large-head toothbrushes with a brush head size of approximately 4 cm (Samjeong Corporation, Seoul, Korea) were used in the analysis. Both types of toothbrushes featured dual-layered micro bristles made with a nylon base, and the height of the toothbrushes was approximately 1.1 cm (Fig. 1).

Fig. 1. The shape of the toothbrush. (A) Large-head toothbrush. (B) Regular-sized toothbrush. Head size: large head, approximately 4 cm; regular sized, approximately 2 cm. Both types of toothbrushes have dual-layered micro bristles.

2) Dental plaque measurement

Participants (n=15) attended two experiment sessions. In the first, the control group used the regular-sized toothbrush; in the second, the experimental group used the large-head toothbrush. All experimental procedures were conducted identically for both sessions. First, the surfaces of the participant’s teeth were photographed using quantitative light-induced fluorescence digital (QLF-D) imaging (AIOBIO, Seoul, Korea) 2 hours after eating without applying a disclosing solution. Then, the modified O’Leary index was measured after applying a disclosing solution to the participant’s teeth. Researchers then provided a one-time in-person educational session on the rolling method using dental models and toothbrush models. Participants brushed their teeth for 3 minutes while looking in a mirror under the guidance of the researchers. Regardless of the toothbrush head size, all participants brushed their teeth with the same amount of toothpaste (0.5 g). In person, the participants were instructed to maintain consistent pressure on the tooth surface while brushing. The oral cavity was divided into eight regions (upper right molars, upper right front teeth, upper left front teeth, upper left molars, lower left molars, lower left front teeth, lower right front teeth, lower right molars), and each region was brushed five times on the cheek side and five times on the tongue side. The surfaces of the participant’s teeth were photographed again using QLF-D, and the plaque index (PI) was measured. To reduce bias, QLF-D imaging and modified O’Leary index measurements were each performed by one researcher.

3) Dental plaque analysis

The fluorescence levels of the QLF-D images were confirmed using the viewer program C3 (AIOBIO). The amount of fluorescence was measured using the analysis program QA2, and the Area R30 value was used to indicate the amount of dental plaque. For the modified O’Leary index measurement, the teeth were divided into four surfaces: cheek, tongue, mesial, and distal. The scoring method was as follows: 100−(number of stained surfaces/total number of surfaces [total number of teeth×4])×100.

4) Measurement of residual toothpaste on the toothbrush

The used toothbrushes were cleaned by shaking them five times in 200 ml of distilled water and then air-dried at room temperature for 2 weeks. The dried toothbrushes (n=15) were weighed using an analytical precision balance (METTLER TOLEDO, Columbus, OH, USA). The amount of residual toothpaste on the toothbrush was calculated by subtracting the weight of the unused identical toothbrushes (n=15) from the weight of the dried toothbrushes. All the toothbrushes used for experiments were cleaned, dried, and weighed using the same process.

3.Statistical analysis

Statistical analyses were performed using IBM SPSS 29.0.1.0 (IBM Corp., Armonk, NY, USA). Differences in the amounts of dental plaque and residual toothpaste in the two groups were analyzed using Wilcoxon’s signed-rank test. The results are expressed as the mean±standard deviation. A p-value ≤0.05 was considered statistically significant.

1.Plaque removal efficacy using regular-sized and large-head toothbrushes

To observe the degree of plaque removal with regular-sized and large-head toothbrushes, QLF-D images were taken and the O’Leary index was measured used 1 hour after a meal. The participants then brushed their teeth with either a regular-sized or large-head toothbrush, and the QLF-D imaging and PI measurements were repeated (Fig. 2A). Comparison of the QLF-D imaging results showed that the fluorescence intensity score significantly decreased from 57.38±49.70 before using the regular-sized toothbrush to 18.38±18.22 after use, with a change of 18.33±10.07 (p=0.002), indicating significant plaque reduction. In contrast, the change in fluorescence intensity score for the large-head toothbrush was from 56.91±71.70 before use to 27.09±33.92 after use, with a change of 10.07±28.83, which was not statistically significant (p=0.156) (Fig. 2B). The O’Leary index measurements showed that the regular-sized toothbrush significantly decrease the PI from 52.83±21.24 before use to 37.06±24.10 after use, with a change of 35.22±20.87 (p<0.001). The large-head toothbrush showed a significant decrease in PI from 50.25±25.03 before use to 41.78±23.85 after use, with a change of 18.33±21.42 (p=0.008) (Fig. 2C).

Fig. 2. The effect of toothbrush head size on dental plaque removal. (A) Acquisition of dental plaque images on tooth surfaces using a quantitative light-induced fluorescence digital (QLF-D) charge-coupled device camera (n=15/group). (B) Graph comparing the degree of dental plaque removal achieved with regular-sized and large-head toothbrushes using AREA R30 values from QLF-D images analyzed with QA2 software. (C) Graph comparing plaque index (PI) scores of regular-sized and large-head toothbrushes. The results are expressed as the mean±standard deviation. p-value was determined using the Wilcoxon signed-rank test.

2.Plaque removal efficacy of regular-sized and large-head toothbrushes by tooth surface area

To observe the plaque removal efficacy of regular-sized and large-head toothbrushes by tooth surface area, PI scores were measured and compared 1 hour after a meal and after brushing. PI scores were measured on the proximal, palatal/lingual, and labial/buccal surfaces (Table 1). On the proximal surface, the regular-sized toothbrush resulted in significant plaque removal, with a change of 9.04±10.83 (p=0.008), whereas the large-head toothbrush showed a non-significant difference of 1.60±7.43 (p=0.310). On the palatal/lingual surface, the regular-sized toothbrush showed a non-significant plaque removal difference of 0.13±3.18 (p=0.524), and the large-head toothbrush also showed a non-significant difference of 2.27±4.42 (p=0.086). On the labial/buccal surface, the regular-sized toothbrush showed a significant plaque removal difference of 4.73±4.95 (p=0.006), while the large-head toothbrush showed a non-significant difference of 0.33±3.68 (p=0.705).

Table 1

Plaque Index Scores by Tooth Position for Regular-Sized and Large-Head Toothbrushes

Category (n=15/group)	Plaque index score		Difference between before and after	p-value
	Before	After
Proximal surface
Regular-sized toothbrush	34.80±12.25	25.73±13.22	9.04±10.83	0.008
Large-head toothbrush	29.87±13.75	28.27±11.70	1.60±7.43	0.310
Palatal/lingual surface
Regular-sized toothbrush	7.07±4.73	6.93±5.23	0.13±3.18	0.524
Large-head toothbrush	8.27±6.73	6.00±3.85	2.27±4.42	0.086
Labial/buccal surface
Regular-sized toothbrush	11.40±7.42	6.67±6.54	4.73±4.95	0.006
Large-head toothbrush	8.73±6.91	8.40±5.62	0.33±3.68	0.705

Values are presented as mean±standard deviation.

p-values were determined using the Wilcoxon signed-rank test (n=15/group).

3.Comparison of the cleaning ease of regular-sized and large-head toothbrushes

Participants received face-to-face brushing education from researchers and before the experiment. The same product was used for both groups (n=15/group). Participants brushed with the same amount of toothpaste (0.5 g), then the toothbrushes were cleaned with distilled water through the same process and allowed to dry for 2 weeks. The ease of cleaning was measured by the amount of residual toothpaste after drying (the weight difference between the used and unused toothbrushes) (n=15/group) (Fig. 3). The weight difference before and after use for the regular-sized toothbrush was 0.23±0.12 g; for the large-head toothbrush, it was 0.62±0.14 g. The difference in the amount of residual toothpaste between the two groups was significant (p=0.043), indicating the large-head toothbrush was not easier to clean than the regular-sized toothbrush.

Fig. 3. Comparison of residual toothpaste after using regular-sized and large-head toothbrushes. The used toothbrushes were cleaned by shaking them five times in 200 ml of distilled water and then air-dried at room temperature for 2 weeks. The amount of residual toothpaste was considered the difference between the weight of the dried used toothbrush and the weight of an identical unused toothbrush (n=15/each group). The results are expressed as the mean±standard deviation. p-value was determined using the Wilcoxon signed-rank test.

1.Interpretation

Since 2013, annual dental scaling has been covered by health insurance for subscribers aged 20 years and older. As interest in oral health management has increased, interest in oral hygiene products has also grown¹³⁾. Consequently, a variety of specialized oral hygiene products have been marketed. According to the oral care market forecast for 2024 to 2032 provided by Fortune Business Insights, the global oral care market was valued at ​＄​​32.61 billion in 2023 and is projected to grow from ​＄​​33.63 billion in 2024 to ​＄46.52 billion by 2032¹⁴⁾. Worldwide, the incidence of oral cancer, tooth decay, and other periodontal diseases is rising, increasing consumer demand for oral care products such as toothpaste, toothbrushes, and mouthwash. Additionally, factors such as increased consumer awareness of health and hygiene, the rise in the number of dental clinics and cosmetic stores, and growing population income are driving market growth. The toothbrush segment is showing significant growth not only for regular toothbrushes but also for advanced brushing products such as rechargeable electric toothbrushes (e.g., the Oral-B iO Series).

Toothbrushes are the most common oral hygiene tool that promotes oral health and prevents dental diseases⁶⁾. The large-head toothbrush has a brush head twice the size of the brush head on a standard toothbrush, making it a popular choice among consumers. While toothbrushes must be effective in managing oral hygiene, proper hygienic management after use is also crucial. Abrasives and surfactants included in toothpaste are necessary for removing dental plaque but may cause contact dermatitis, hives, rhinitis, and angioedema⁹⁾. Additionally, used toothbrushes can become contaminated by microorganisms present in the mouth, and these microorganisms can lead to recontamination of the oral cavity, necessitating measures to minimize bacterial growth¹⁵⁾. Toothbrushes used for a long period can be contaminated by various microorganisms such as Streptococcus, Staphylococcus, Lactobacilli, Pseudomonas, Klebsiella, Escherichia coli, and Candida¹⁶⁾. These microorganisms can cause cavities, gingivitis, stomatitis, and infective endocarditis. Moreover, contaminated toothbrushes can be associated with the transmission of serious health problems such as heart disease (infective endocarditis), arthritis, bacteremia, and stroke⁴⁾. While the large-head toothbrush is favored for its ability to brush multiple teeth at once, its effectiveness in managing dental plaque and hygiene has not been verified. The design of the toothbrush, including the size of the brush head, impacts the residual bacteria left on the toothbrush after use. This study aimed to evaluate the effectiveness of large-head toothbrushes in removing dental plaque and maintaining hygiene compared that of regular-sized toothbrushes.

2.Comparison with previous studies

With the introduction of toothbrushes with different head sizes, there is a need to analyze their dental plaque removal efficacy and their effect on hygiene management. However, no previous reports exist on this matter. There are studies that have examined the degree of microbial contamination based on different storage methods after toothbrush use and suggested appropriate washing temperatures for toothbrush cleaning¹⁰⁾. Nevertheless, these studies are limited to regular-sized toothbrushes, lacking comparative analyses to evaluate their plaque removal efficacy and effect on hygiene management. Additionally, while there have been reports comparing the amount of toothpaste used and the time required for brushing based on the shape of the toothbrush head, these studies did not evaluate the efficiency of plaque removal or the effects on hygiene management^11,12). We examined the plaque removal efficacy of large-head toothbrushes using QLF-D imaging and the PI. QLF-D is an analytical tool that sensitively detects fluorescence depending on the amount of dental plaque using a charge-coupled device camera, allowing for the quantification of dental plaque¹⁷⁾. The O’Leary index is used to evaluate plaque attachment after staining the tooth surface, assigning individual plaque scores to each tooth surface (mesial, distal, buccal, and lingual)¹⁸⁾. This provides a detailed assessment of plaque distribution in the mouth. Therefore, it is suitable for individual patient monitoring and large-scale clinical studies and a useful indicator for evaluating oral hygiene interventions and products. Our analysis revealed that large-head toothbrushes generally had a lower plaque removal efficacy than that of regular-sized toothbrushes. Regular-sized toothbrushes were effective in removing plaque from the proximal and labial/stenotic surfaces, but less effective for the palatal/lingual surfaces. Large-head toothbrushes had lower plaque removal efficacy on all proximal, palatal/lingual, and labial/stenotic surfaces. The difference in plaque removal efficacy between the two types of toothbrushes was greatest on the labial/constriction surfaces. Therefore, it is recommended to pay particular attention to all proximal, palatal/lingual, and labial/stenotic surfaces when using a large-headed toothbrush.

To assess the toothbrush’s effect on hygiene management, we measured the amount of toothpaste remaining after brushing. Participants brushed with the same amount of toothpaste and rinsed the used toothbrushes in the same manner, and bristles were allowed to dry thoroughly. The amount of remaining toothpaste was calculated by subtracting the pre-use weight of the toothbrush from the post-use weight. Compared to the regular-sized toothbrush, the large-head toothbrush showed a significant difference in the remaining amount of toothpaste, indicating that it is not as easily cleaned as the regular-sized toothbrush. Consequently, based on the results of plaque removal and toothpaste residue tests, the large-head toothbrush was less effective in overall oral hygiene management than the regular-sized toothbrush.

3.Limitations

Although the consumer purchase rate for large-head toothbrushes is high, our results indicate it is necessary for consumers to be aware of the weaknesses of large-head toothbrushes for maintaining oral hygiene. This study was conducted according to an analysis protocol with human participants, which limited the number of participants. Evaluating the overall oral health status, such as PI, gingivitis index, and gingival bleeding index, and assessing the hygiene status of the toothbrush with a larger number of participants using the large-head toothbrush over a longer period would help generate more definitive information about the advantages and disadvantages of large-head toothbrushes.

4.Conclusions

In this study, we compared the utility and hygienic management of the large-head toothbrush as an oral hygiene tool with that of the regular-sized toothbrush. The large-head toothbrush was found to have generally lower plaque removal efficacy and was herder to clean than the regular-sized toothbrush. These results provide significant information for consumers when choosing a toothbrush and highlight the considerations for using a large-head toothbrush.

None.

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. EU24-03). All subjects voluntarily participated in the study after providing written informed consent.

Conceptualization: Ji-won Lee, Myoung-Hee Kim, Koung-hee Kim, Da-bin Han, Yu-jin Hwang, and Young Sun Hwang. Experiments: Ji-won Lee, Myoung-Hee Kim, Koung-hee Kim, Da-bin Han, Yu-jin Hwang, and Young Sun Hwang. Data acquisition: Ji-won Lee, Myoung-Hee Kim, Koung-hee Kim, Da-bin Han, Yu-jin Hwang, and Young Sun Hwang. Formal analysis: Ji-won Lee, Koung-hee Kim, Da-bin Han, Yu-jin Hwang, and Young Sun Hwang. Funding acquisition: Young Sun Hwang. Supervision: Young Sun Hwang. Writing-original draft: Ji-won Lee, Myoung-Hee Kim, Koung-hee Kim, Da-bin Han, Yu-jin Hwang, and Young Sun Hwang. Writing-review & editing: Young Sun Hwang.

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).

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.