Key takeaways
- The ISO size printed on a pack comes from ISO 16409:2016, which only covers manual brushes with a round head on a wire stem. Plastic core brushes, powered brushes, floss, tape and filament free picks all sit outside that standard, so they carry no ISO size at all.
- The UK Delivering Better Oral Health toolkit states there is “no evidence to determine whether interdental cleaning aids reduce caries” against brushing alone. Its case for cleaning between your teeth rests on gum health.
- The same toolkit says interdental brushes may work better than floss, and tells clinicians to keep floss for gaps too tight to take a brush.
- TePe’s Original red ISO 2 pack sat at number 3 in Amazon UK’s entire Health and Personal Care chart when we looked on 18 September 2026. We priced six options the same day, from £4.50 to £12.90.
A bag of 20 little brushes is an odd thing to find near the top of a bestseller chart. On 18 September 2026 the TePe Original red pack was number 3 across the whole of Amazon UK’s Health and Personal Care list, ahead of creatine, turmeric and most of the vitamin aisle. Two more TePe colours and several own brand silicone picks sat in the same search results, all of them selling steadily, with no spike behind it.
So it is worth getting the buying decision right, and the buying decision turns almost entirely on size. That is where nearly every guide to these things goes quiet, because the numbers on the packets are not all measuring the same thing, and some of them are not measuring anything standardised at all.
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Prices and specs last checked 18 September 2026 · how we picked
What the ISO number on the packet covers, and what it leaves out
When a pack says ISO 2 or ISO 0, it is referring to ISO 16409:2016, Dentistry. Oral care products. Manual interdental brushes. We read the scope at ISO on 18 September 2026. It is the second edition, published in October 2016, and it was reviewed and confirmed in 2025, so it is still the current version.
Read the scope and the useful part is what it refuses to cover. The standard applies to manual brushes with a round cross section head, made of a wired stem with filaments inserted into it. Brushes with a plastic core are excluded outright. It also says plainly that it does not apply to powered interdental brushes, manual toothbrushes, dental floss, tapes, strings, or interdental cleaners that contain no filaments.
That last exclusion matters in a UK supermarket or on an Amazon results page, because the soft silicone picks sold alongside the wire brushes are exactly the thing ISO 16409 does not reach. A 110 piece bag can honestly advertise five sizes and still have no ISO size on it anywhere, because there is no ISO scale for it to sit on. The sizes are the maker’s own.
Brands that do make wire brushes still label them in their own way. Of the six packs we priced, three carry an ISO number, and three do not. Curaprox sells a Perio refill as CPS 405. Wisdom sells a size called Fine Blue. TePe prints an ISO number and a millimetre figure together, which is why its packs are the ones people quote at each other. None of this is deceptive, and all of it means the same thing in practice: the number on the box tells you where a brush sits in that brand’s own range, and nothing more reliable than that.
Which leads to the only sizing advice that survives contact with reality. You size to the gap, not to the brand. The UK guidance says the brush should fit snugly in the space without the wire rubbing against the tooth, and that people with larger spaces will need more than one size, because the gaps in one mouth are not all the same. A mixed pack costs less than a fiver and answers the question in a week. A 20 pack of the wrong size answers nothing.
What the UK guidance actually claims for these brushes
Chapter 8 of Delivering Better Oral Health, the prevention toolkit issued jointly by the Department of Health and Social Care, the Welsh Government, the Department of Health Northern Ireland and NHS England, was updated on 10 September 2025. We read it on 18 September 2026. It is more cautious than the packaging.
On gums, the toolkit describes the evidence that cleaning aids such as interdental brushes and floss reduce gingivitis and plaque as low to very low certainty, and says the clinical importance of the effect sizes is uncertain. On decay it goes further and says there is “no evidence to determine whether interdental cleaning aids reduce caries” when compared with toothbrushing alone, because the trials it drew on were at unclear or high risk of bias and reported plaque and gingivitis instead.
None of that is a reason to stop. The same chapter still recommends daily cleaning between the teeth to below the gum line, ideally through adult life, and suggests doing it before you brush so the two habits link up. Where the toolkit is confident is the choice between tools: it reports that interdental brushes may be more effective than floss, and for people with or treated for periodontitis it says brushes are more effective than floss or tape, with floss kept for spaces too tight to take a brush. The NHS advice page for the public lands in the same place, describing brushes or single tufted brushes as something you can use instead of flossing, especially where there are gaps, and warning against poking wooden toothpicks between your teeth.
So the honest version is this. Buy these for your gums, on guidance that is real but thinner than the marketing suggests. Do not buy them expecting to stop a cavity, because the government’s own toolkit says nobody yet knows whether they do. And if your gums bleed for more than a few days once you start, that is a conversation with a dentist or hygienist, not a cue to buy a bigger size.
How we picked these
We have not used these in a clinic and we make no claim to have tested cleaning performance. What we did do on 18 September 2026 was read the scope of ISO 16409:2016 at ISO, read chapter 8 of the UK toolkit and the NHS advice page, then work through Amazon UK’s Health and Personal Care chart and search results, verify each product page individually for title, price and stock, and pick six that cover different gap sizes and different reasons for choosing. Three of the six carry an ISO size and three do not, which is the point and not an oversight. Prices below are what we read on the day.
How they compare
| Pick | Best for | Size marking | Pack | Price |
|---|---|---|---|---|
| TePe Original Mixed Pack | Working out your sizes | ISO 0 to 7, 0.4 to 1.3mm | 8 brushes | £4.50 |
| TePe Original Red | Everyday medium gaps | ISO 2, 0.5mm | 20 brushes | £9.90 |
| TePe Angle Yellow | Reaching back teeth | 0.7mm, no ISO number shown | 25 brushes | £12.90 |
| Curaprox CPS 405 Perio | Wider spaces after gum treatment | CPS 405, no ISO number | 4 brush refill | £6.95 |
| Wisdom Clean Between Fine | Stocking up cheaply | Fine Blue, no ISO number | 3 packs of 20 | £7.20 |
| Silicone pick bag, 110 pieces | People who cannot get on with wire | 5 own brand sizes, outside ISO 16409 | 110 pieces | £9.99 |
The six picks
TePe Interdental Brush Original, Mixed Pack
ISO 0 to 7 · 0.4 to 1.3mm · 8 brushes · rated 4.6 · £4.50
Eight brushes covering the range from the narrowest to one of the widest, which is the cheapest way to find out what your own mouth needs before committing to a colour. Work along the gaps, keep the ones that slide in with a little resistance and no scraping, then buy that size in a 20 pack. At £4.50 it costs less than guessing once.
The catch: It is a sampler, so you get one or two of each and nothing lasts. Several of the eight will turn out to be useless for you, which is what you are paying to find out.
Check price on Amazon →TePe Interdental Brush Original, Red, 0.5mm ISO 2
ISO 2 · 0.5mm · 20 brushes · rated 4.6 · £9.90
This is the pack doing the volume. It was sitting at number 3 in the whole Health and Personal Care chart on the morning we checked, which for a red plastic handle and a bit of wire tells you how many British mouths have settled on ISO 2 as their default. The handle is short and flat, so it holds well against a wet thumb, and the filaments keep their shape for a good few uses.
The catch: ISO 2 is only right if ISO 2 is right for you. Buying this first, on the strength of it being the popular one, is how people end up with 20 brushes that either rattle in the gap or refuse to go in.
Check price on Amazon →TePe Angle Interdental Brush, Yellow 0.7mm
0.7mm · angled head · 25 brushes · rated 4.6 · £12.90
The back molars are where interdental cleaning usually falls apart, because a straight handle asks your wrist to do something it cannot. The Angle puts the brush head out at roughly a right angle on a longer flat handle, so you can come at the gap from the front of the mouth instead of trying to get behind it. If you have been skipping the last two teeth on each side, this is the fix.
The catch: Roughly 52p a brush against 50p for the straight Original, and the listing gives a millimetre figure with no ISO number, so if you already know your ISO size you have to work back from the millimetres to match it.
Check price on Amazon →Curaprox CPS 405 Perio Refill
CPS 405, no ISO number · 4 brush refill · rated 4.7 · £6.95
Curaprox builds these as refill heads for its own holder, so the handle stays and the head goes, which suits anyone cleaning larger spaces daily and getting through brushes. The Perio line is aimed at the wider gaps that come with gum tissue loss, the situation the UK toolkit specifically says calls for a brush over floss. The filaments are dense enough to fill a space that a supermarket brush swims in.
The catch: The pack is four heads, so the cost per brush is high next to a 20 pack, and you need the Curaprox handle to use them. The CPS numbering is the brand’s own, so the packet gives you nothing to compare against an ISO size.
Check price on Amazon →Wisdom Clean Between Interdental Brushes, Fine Blue, 3 packs of 20
Fine Blue, no ISO number · 60 brushes · rated 4.6 · £7.20
Sixty brushes for £7.20 works out at 12p each, roughly a quarter of what the TePe packs cost per brush, from a British brand that has been in bathroom cabinets here for decades. For a habit you are trying to make stick daily, the price per brush is not a trivial detail. Handles are longer and rounder than TePe’s flat ones, which some people prefer.
The catch: Fine Blue is Wisdom’s own size name with no ISO number to translate it, so you cannot map it onto a TePe size without trying it. The wire is noticeably springier, and at this price the filaments splay sooner.
Check price on Amazon →Silicone interdental pick bag, 5 sizes, 110 pieces
5 own brand sizes · outside ISO 16409 · 110 pieces · rated 4.5 · £9.99
Some people never get on with a wire stem, and a soft tapered silicone pick is gentler to push into a gap you are still getting used to. A bag of 110 in five widths is cheap enough to keep one in a bag, one in a desk and one in the car, which is usually what decides whether anything gets cleaned at all.
The catch: These are the products ISO 16409 explicitly does not cover, so the five sizes are the seller’s own and answer to nothing. The UK toolkit’s comparison of brushes against floss does not extend to silicone picks either, so you are further from the evidence than you are with a wire brush.
Check price on Amazon →Common questions
Which size do I need?
Nobody can tell you from a chart, and that includes us. The UK toolkit’s test is whether the brush fits snugly in the space without the wire rubbing the tooth, and it points out that people with larger gaps will need several sizes for different spaces in the same mouth. A mixed pack is the cheap way through it, and a dentist or hygienist can size you properly at a check up.
Are interdental brushes better than floss?
The UK toolkit reports that brushes may be more effective, and for people with or treated for periodontitis it says brushes are more effective than floss or tape. It keeps floss for spaces too tight to take a brush. The NHS advice page says much the same to the public: use brushes instead of flossing, especially where there are gaps.
Will they stop me getting cavities?
On the government’s own reading, unknown. Chapter 8 says there is no evidence to determine whether interdental cleaning aids reduce caries against brushing alone, because the trials measured plaque and gingivitis instead. Fluoride toothpaste at 1,350 to 1,500ppm is what the toolkit puts at the centre of decay prevention.
Before or after brushing?
The toolkit suggests cleaning between the teeth before you brush, as a way of linking the new habit to one you already have. It recommends doing it daily, and cleaning to below the gum line.
Do the silicone picks count as interdental brushes?
Not under the standard. ISO 16409:2016 covers manual brushes with a round head on a wire stem and states it does not apply to interdental cleaners without filaments, so the soft picks fall outside it, along with plastic core brushes and powered ones. They may still suit you. They just have no standardised size scale behind the numbers on the bag.
Sources
- Delivering better oral health: chapter 8, oral hygiene, GOV.UK, updated 10 September 2025, read 18 September 2026.
- ISO 16409:2016, Dentistry. Oral care products. Manual interdental brushes, ISO, read 18 September 2026.
- How to keep your teeth clean, NHS, read 18 September 2026.
Prices and stock were read on Amazon UK on 18 September 2026 and change often; the button shows the current Amazon price. This page is general information about products, not dental advice, and it is no substitute for seeing a dentist or hygienist. Look Into is a participant in the Amazon EU Associates Programme and earns from qualifying purchases, at no extra cost to you.