What Is Dental Floss Made Of?

Almost all dental floss is nylon or PTFE — the polymer family behind non-stick cookware — spun into a filament and coated with wax and flavouring. You won't find that written on the box. Floss is regulated as a medical device, so unlike toothpaste, it carries no required ingredient list.

Why doesn't floss come with an ingredient list?

Because it isn't a cosmetic. The FDA classifies dental floss as a Class I medical device — the lowest-risk category — subject to general controls only, and exempt from premarket notification.

That means no agency reviews a floss before it reaches the shelf, and no rule requires the manufacturer to say what it's made of. Your toothpaste must list every ingredient. The string you pull between your teeth every night does not.

The regulation is also showing its age. It still describes floss as "a string-like device made of cotton or other fibers." Almost nothing on the shelf today is cotton.

So what are the filaments?

Two materials dominate, and both are plastics.

Nylon multifilament is many fine strands twisted into one thread, and it's what most spooled floss is made of. Because it's built from many fibres, it can splay slightly and spread across the tooth surface. It can also come apart, which is what shredding is.

PTFE monofilament is one smooth strand of polytetrafluoroethylene, better known as Teflon, and it's what "glide"-type flosses are made of. It slips through tight contacts and rarely shreds.

Nylon and PTFE are both man-made plastics, just built differently: one is a twisted bundle, the other a single strand. Silk, the original floss material, is the third option, the oldest by far, and the only one of the three that isn't plastic.

What is the coating actually doing?

More than most people assume. Most floss is waxed, and that wax is frequently microcrystalline or paraffin — both petroleum-derived. Some brands use beeswax or candelilla instead, with flavour and sweetener on top.

The coating isn't permanent. A 2022 study in Materials examined four commercial flosses under electron microscopy before and after use, and found one had lost most of its wax coating through normal flossing. Another showed individual fibres already broken, with elongation at break rising from roughly 50% to 150% after use.

Waxed floss before and after use 

The wax is doing much of the work of holding the filament together — and it comes off while you use it.

Frequently asked questions

What is dental floss made of? Most modern dental floss is either nylon, spun as many fine filaments twisted together, or PTFE (polytetrafluoroethylene), a single smooth monofilament of the same polymer used in non-stick coatings. Both are usually coated in wax — often petroleum-derived microcrystalline or paraffin wax — plus flavouring. A few oral care brands still make silk floss, the original material today. An example is Dr. Jen.

Is dental floss FDA approved? The FDA classifies dental floss as a Class I medical device subject to general controls only, and it is exempt from pre-market notification. That means no agency reviews an individual floss product before it goes on sale. "FDA approved" is not a claim any floss can accurately make.

Does dental floss contain Teflon? Some does. PTFE — polytetrafluoroethylene, the polymer sold under the brand name Teflon — is used to make smooth monofilament floss that slides easily between tight teeth. Packaging rarely names it, since floss is not required to carry an ingredient list.

Why is there no ingredients on dental floss? Because it's regulated as a medical device. Cosmetics and toothpastes must declare their ingredients; Class I devices like floss carry no such requirement. Any brand that lists its materials is choosing to.