Interdental Care: Floss, Interdental Brushes & Water Flossers — Evidence‑Based Guide

Is Toothbrushing Alone Enough? Scientific Truths About Interdental Care from a Periodontal Specialist — Dr. Hiroshi Miyashita, Director, Tokyo International Dental Clinic Roppongi

Experience
I am Dr. Hiroshi Miyashita, Director of Tokyo International Dental Roppongi. For many years I have specialized in periodontal treatment and preventive guidance. In clinical practice I frequently hear patients say, “I brush every day, but my gums are swollen,” or “My checkup found plaque between my teeth.” I have seen many cases where interdental plaque—areas toothbrushes cannot reach—becomes the nidus of chronic inflammation.

Expertise

Evidence‑based approach: I evaluate interdental care effectiveness based on high‑quality studies including the Cochrane review (Worthington et al., 2019).
Products and indications: I understand the characteristics and clinical indications of floss, interdental brushes, and oral irrigators (water flossers) and tailor recommendations to each patient’s oral morphology.
Outcome measures: I use clinical indices such as the Gingival Index (GI) and plaque indices to assess short‑ and mid‑term outcomes in routine practice.

Authority
Systematic reviews that aggregate randomized controlled trials are reliable for assessing evidence quality; I apply these findings within clinical guidelines and practice.

Trustworthiness
I propose optimal care combining scientific evidence and clinical experience. I honestly explain the limits of the evidence (GRADE ratings often low to very low) and respect each patient’s individual decision.

Main points and clinical implications

Interdental brushes can be a promising first choice
The Cochrane review suggests that adding an interdental brush to toothbrushing may be more effective than brushing alone in reducing gingival inflammation (GI) and plaque. In adults with adequate interdental space, interdental brushes are often a practical and effective option compared with floss.
Floss is not useless — individual factors matter
Floss remains useful for tight contacts and narrow gaps. Optimal device selection depends on interdental space, manual dexterity, and motivation. The key is not a universal best tool but whether it fits the individual’s mouth.
Oral irrigators have limited, mainly short‑term, benefits
Water flossers may reduce gingival inflammation in the short term (around one month), but evidence for sustained benefits at 3–6 months is unclear. There is limited evidence that they surpass toothbrushing in plaque removal; they should be considered adjunctive tools.
Long‑term evidence for caries prevention and periodontal progression is insufficient
Currently, robust long‑term evidence that interdental devices reduce proximal caries or halt progression to severe periodontitis is lacking. This reflects an evidence gap—long‑term, high‑quality studies are needed.
Safety is high, but evidence certainty is low
Serious adverse effects are rare. However, many studies are difficult to blind and enroll relatively healthy participants, so the overall certainty of evidence is rated low to very low. Statistical significance does not always equate to clinically meaningful benefit for every patient.

Clinical practical flow (our clinic’s recommendation)

Step 1: Assess interdental morphology (presence/absence of gaps) and plaque locations.
Step 2: If interdental spaces are present, recommend an appropriately sized interdental brush; use floss for narrow contacts.
Step 3: If adding a water flosser, monitor clinical outcomes regularly.
Step 4: Reassess after ~3 months; if insufficient benefit, adjust tools or techniques. Combine with regular professional care.

Reference
Worthington, H. V., MacDonald, L., Pericic, T. P., Sambunjak, D., Johnson, T. M., Imai, P., & Clarkson, J. E. (2019). Home use of interdental cleaning devices, in addition to toothbrushing, for preventing and controlling periodontal diseases and dental caries. Cochrane Database of Systematic Reviews, (4).

Conclusion — Message to patients
“Brushing alone is not always enough” — this is the important message from the science. However, the optimal interdental care is not one‑size‑fits‑all. Consider interdental space, ease of use, sustainability, and your oral condition, and together we will select the most suitable tool. Evidence evolves; based on the latest science and my clinical experience, we provide practical care tailored to you. Please visit for an interdental checkup.

Make an appointment for consultation today.

Tokyo International Dental Clinic Roppongi

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