Research Confirms Interdental Cleaning with Itoyoji® Can Lead the Oral Microbiome to a Healthy Balance

Kobayashi Pharmaceutical Co., Ltd. (Headquarters: Osaka City, President: Yoshikazu Toyoda), through commissioned research to a research group led by Dr. Takeshi Yamanaka of the Faculty of Healthcare, Osaka Dental University (Headquarters: Hirakata City, Osaka Prefecture, Chairman: Takaaki Kawazoe), has discovered that interdental cleaning with dental floss (Itoyoji®) may change the composition of the oral microbiome (oral flora*1) to a healthier balance. The results of this study, suggesting that daily interdental care can improve the quality of the oral environment and lead to a healthy balance, were published online in the international academic journal "BMC Oral Health" on April 22, 2026. (https://doi.org/10.1186/s12903-026-08353-z)

[Key Points of Research Results]
- Suggests that continuous interdental cleaning with Itoyoji® can change the oral flora and lead to a healthy balance.
- Confirmed that the occupancy rate of specific "bacterial phyla to which periodontal disease-related bacteria belong" significantly decreases with interdental cleaning.
- Scientifically verified changes in the oral environment due to "cleaning" using genetic analysis technology (metagenomic analysis).

[Research Background]
Over 700 types of bacteria inhabit the oral cavity, and a disruption in the balance of these bacteria, known as oral flora, contributes to periodontal disease and tooth decay. In recent years, it has been academically discussed that the state of the oral environment may be related to systemic health conditions; however, the impact on specific diseases requires further verification.
Particularly, the spaces between teeth are areas where dirt is likely to remain when using only a regular toothbrush, making it easy for bacteria to colonize. To verify how interdental cleaning with dental floss, which has been recommended as a habit despite insufficient scientific data, affects the oral bacterial composition, we conducted this study using comprehensive genetic analysis technology.

[Research Details]
1. Suggests interdental cleaning with Itoyoji® can change (impact) oral flora
Previously, although interdental cleaning had been recommended by dental professionals, there was not always sufficient direct scientific evidence regarding its impact on the composition of the oral microbiome (flora). In this study, a rigorous 8-week intervention trial was conducted with 15 healthy adults, alternating every 2 weeks between a period of normal tooth brushing only and a period using dental floss (Itoyoji®) in addition to brushing. (Figure 1)
As a result of "16S rRNA metagenomic analysis*2" using a next-generation sequencer, it was confirmed that the proportion of Gram-positive bacteria increased in approximately two-thirds of the subjects after using dental floss. This suggests that local interdental cleaning in addition to a toothbrush changes the oral flora.
Used dental floss (Itoyoji®)
Figure 1: Test Method

2. Confirmed significant decrease in specific "bacterial phyla" that increase periodontal disease risk
It was confirmed that continuous interdental cleaning significantly reduced the Fusobacteriota and Bacteroidota phyla, to which some periodontal disease-related bacteria belong. (Figure 2) Furthermore, instances were observed where the red complex*3, previously held by some participants, was no longer detected after the intervention.
Figure 2: Changes in the composition of bacterial phyla in proximal dental plaque / ★: Significant difference (t-test, p<0.05)

3. Possibility that interdental cleaning leads oral flora to a healthy balance. Suggests increase in bacterial groups related to vascular health
Through continuous interdental cleaning, a tendency was confirmed to improve the occupancy rate of the genus Rothia, a nitrate-reducing bacteria considered related to vascular health through the generation of nitric oxide. This is an important finding capturing the possibility that interdental care goes beyond mere cleaning and leads the oral flora to a healthy balance.

[Conclusion]
This study scientifically demonstrated the possibility that interdental cleaning not only removes physical dirt but also helps maintain a healthy oral bacterial ecosystem. Regulating the oral environment is fundamental to maintaining health, and the daily use of "Itoyoji®" is expected to become an important habit supporting a healthy life.
We will continue to advance research deepening these findings, convey the importance of regulating the oral flora to consumers, and strive to contribute to society through oral health.

*1 What is Oral Microbiome (Oral Flora)
A collection of various bacteria inhabiting the mouth. The composition (types and proportions of bacteria) varies among individuals.
*2 16S rRNA Metagenomic Analysis
A comprehensive analysis method for determining the types and proportions of bacteria present in a sample by reading specific gene sequences possessed by bacteria.
*3 Red Complex
Three types of bacteria (P. gingivalis, T. forsythia, T. denticola) considered to be particularly pathogenic among periodontal disease bacteria.