How to Floss When Your Gums Bleed, and How Floss Differs From Interdental Brushes

Floss cleans plaque from between the teeth and in the gum crevice, where a toothbrush cannot reach. The Korea Disease Control and Prevention Agency (KDCA, 질병관리청) says gum disease usually starts between the teeth, so tools such as floss, interdental brushes and oral irrigators should be used at least once a day. Floss is pressed against the side of a tooth and moved slowly up and down; it should not be forced hard into the gum or yanked. Bleeding when you first start flossing is often a sign that the spot was already inflamed, and bleeding usually decreases if you keep flossing gently.

Published 2026-11-08 · Updated 2026-11-08 · DentalStatics editorial team

Key facts

How often to clean between teeth	Gum disease usually starts between the teeth, so floss, interdental brushes or similar tools are used at least once a day (source: KDCA National Health Information Portal)
How to use floss	Press it against the side of the tooth and move it slowly up and down to wipe off plaque (source: KDCA National Health Information Portal)
Caution	Pushing in or pulling too hard can injure the gums (source: KDCA National Health Information Portal)
Does it make gaps between teeth wider?	Floss can be used once teeth have erupted, and it does not widen the spaces between teeth (source: KDCA National Health Information Portal)
Order of use	After brushing, clean between the teeth once more with an interdental brush or floss (source: KDCA National Health Information Portal)

Why is brushing alone not enough?

Toothbrush bristles clean the outer, inner and chewing surfaces of teeth well, but they do not reach well into the contact sides where neighboring teeth touch or the gum crevice beneath them. The KDCA describes floss as a tool that cleans between the teeth and in the gingival sulcus (the gap where tooth meets gum).

Gum disease often begins in exactly these spaces between teeth. If the spots that bleed when you brush are mostly between the teeth, plaque there is likely to remain no matter how hard you brush. Cleaning once more with floss or an interdental brush after brushing is the shortest route to less gum bleeding.

How do you use floss?

Cut a generous length of floss, wind it around the middle fingers of both hands, and hold it short with the thumb and index finger to control it. If winding it around your fingers is difficult, the KDCA says you can tie the ends into a loop and hang it over your fingers or palm. Floss with a handle is another option.

At first, practice in front of a mirror starting with the front teeth, then extend to the back teeth as you get used to it. If you cannot clean every gap at once, taking care of the spots that bleed often and the spots where food gets stuck every day is enough to help reduce gum bleeding.

Place the floss on the contact point between the teeth and ease it through with a gentle back-and-forth motion
Hug the floss against the side of one tooth and lower it gently to just below the gum line
Move it slowly up and down along the tooth surface to wipe away plaque
Clean the side of the opposite tooth in the same gap in the same way
Switch to a clean section of floss when moving to the next gap
Do not force it hard into the gum or snap it out

Can I keep flossing if it makes my gums bleed?

It is common for several gaps between the teeth to bleed when you first start flossing. This is usually not because the floss is hurting the gums, but because gums inflamed by leftover plaque bleed at small irritations. As long as you use it gently along the tooth surface without force, it is right to keep using floss.

With steady use, inflammation settles and bleeding generally decreases. On the other hand, if the same spot keeps bleeding despite careful flossing, if the floss catches or shreds, or if the spot is swollen and sore, there may be tartar, a cavity or a problem at the edge of a restoration, so have it checked at a dental clinic.

Should I use floss or interdental brushes?

Floss suits tight gaps where teeth are packed closely, while interdental brushes clean better where the gums have receded and the spaces between teeth have opened, or where there are large gaps such as between the roots of molars. Even in one mouth, the right tool can differ from place to place.

The KDCA explains that you should pick an interdental brush size that can clean both sides of the teeth well, and that a brush with an angled neck is good for reaching the back teeth. Hold the handle and move it back and forth three or four times without forcing it in; if it hurts the gums, change the size, and replace it with a new one if the wire is bent and rubs against the teeth.

How should I care for implants or dental restorations?

The KDCA advises that around an implant, cleaning between implants and along the gum border with thick floss is effective for preventing inflammation, and that a water jet using water pressure also helps. If the gums around an implant bleed or swell, it may mean inflammation has developed around the implant, so have the condition checked at a dental clinic separately from cleaning at home.

Ordinary floss cannot pass between teeth joined in a restoration such as a bridge, so use tools that can pass under the restoration, such as stiff-ended floss or interdental brushes. To learn which tool suits you, the most accurate way is to ask the dentist to show you directly at a regular checkup.

Common myths and facts

Myth: Flossing makes the spaces between teeth wider

The KDCA explains that floss does not widen the spaces between teeth. If the gap looks bigger after flossing, it is often because swollen gums have settled down.

Myth: If floss makes the gums bleed, they are being hurt and you should stop

The blood at the start is mostly due to inflammation that was already there. Gentle, steady use reduces inflammation and bleeding along with it.

Frequently asked questions

When is the best time of day to floss?

The recommended order is to clean once more with floss or an interdental brush after brushing, at least once a day. If you do it only once, the time before bed is best, since plaque builds up easily overnight.

Should children use floss too?

The KDCA says floss can be used once teeth have erupted. Because children find it hard to do themselves, a parent can do it for them with handled floss or similar, starting with the spots where food often gets stuck between the teeth.

Floss keeps catching and shredding between certain teeth.

There may be tartar at that spot, the tooth surface may be rough from a cavity, or the edge of a filling or restoration may be lifted. If it happens repeatedly at the same spot, have it checked at a dental clinic.

How do I choose an interdental brush size?

The right size goes in without force and has bristles that touch both sides of the teeth when inserted. If it does not fit and you push it, you will injure the gums, so go down one size, and if the sizes differ from place to place, use several sizes together.

Is an oral irrigator enough on its own?

The KDCA introduces floss, interdental brushes and oral irrigators together as tools for cleaning between teeth. It is best to have the dentist look at your gums and advise which tool fits your teeth best. Depending on the gap size and whether you have restorations, you can mix floss, interdental brushes and an oral irrigator.

References

Korean version →