Last updated 12 November 2026. Written by the Clean Smile Home team. We sell Oral-B replacement brush heads, so we have an obvious interest in you buying them. We've tried to be straight about what the evidence does and doesn't show. We don't run our own tests; the figures below come from the studies, manufacturers and reviewers we name in the sources.
The short answer
Change your electric toothbrush head about every three months, or sooner if the bristles are splayed, the indicator bristles have faded, or the head smells. That's the advice from Oral-B, Philips and the American Dental Association. Research suggests the state of the bristles matters more than the date, so check the head as well as the calendar.
Where the three-month rule comes from
Almost every brand and dental body lands on the same number, with small differences in wording.
| Source | What it says | Notes |
|---|---|---|
| Oral-B (UK iO head page) | Replace every 3 months, or sooner if the head becomes worn | iO Ultimate Clean heads have bristles that fade from blue to white |
| Oral-B iO manual | Replace every 3 months; indicator colour fades halfway in about 3 months | If bristles splay before the colour fades, you may be pressing too hard |
| American Dental Association | Every three to four months, or sooner if bristles are matted or frayed | Says brush effectiveness drops as bristles wear |
| Philips UK | Every three months, citing NHS advice | Change sooner if bristles look ragged, the head smells or teeth don't feel clean |
| Expert Reviews | At least every three months | Replace as soon as possible if bristles are frayed |
| Currys | Every three months, citing the NHS | Says heavy pressure, braces and frequent brushing shorten head life |
One thing worth knowing: Philips and Currys both credit the three-month figure to the NHS. When we checked the main NHS page on keeping your teeth clean (last reviewed June 2025), it covered brushing twice a day for about two minutes with fluoride toothpaste but didn't give a replacement interval. Philips links to an NHS Devon leaflet for its version. So the advice is NHS-backed locally, but you won't find it on the headline NHS teeth page.
What the research says about worn bristles
The three-month rule is a sensible rule of thumb rather than a precise scientific finding. Two Dutch studies are the most useful here.
Van Leeuwen and colleagues, 2019
Published in the International Journal of Dental Hygiene, this study followed people for a year as they each used manual toothbrushes for three months at a time. The researchers scored each brush's wear on a five-point scale (0 for no wear up to 4 for extreme wear) and measured plaque.
- 516 brushes from 172 people were analysed.
- There was a weak link between more wear and more plaque.
- Brushes with extreme wear were associated with a plaque index of 1.98, against 1.71 for brushes with no visible wear.
- The biggest difference was 13.6%, just under the 15% the ADA uses as a threshold for a clinically meaningful difference.
- People tended to wear their brushes the same way each time. Heavy wearers were heavy wearers on every brush.
The authors' recommendation was to replace a brush before it reaches wear score 2, which is roughly when the outer tufts are splayed out beyond the base of the head. They suggested splaying is a better guide than the brush's age.
Rosema and colleagues, 2013
This earlier study, summarised by TePe, had 50 people professionally brushed with both a new toothbrush and a three-month-old one. It didn't find a clinically relevant difference in plaque removal between new and three-month-old brushes. But the authors noted that wear seemed to affect how well a brush cleaned, and stressed changing a brush when it shows signs of wear.
What this means for you
Two honest caveats. Both studies used manual brushes, not electric heads, and both looked at plaque over short periods rather than long-term gum health. So nobody has proved that day 91 is when an electric head stops working.
What the evidence does support is this: a head that's splayed cleans a bit less well, and some people wear heads out much faster than others. If yours look flattened after six weeks, three months is too long for you. If they still look new at three months, that's the point to change anyway, because the bristle tips also round off and collect bacteria in ways you can't see.
How to tell your head needs changing
The indicator bristles have faded
Most Oral-B heads, including iO heads, have coloured indicator bristles. Oral-B's iO head page says they fade from blue to white. The iO manual says the colour should fade about halfway in roughly three months of normal brushing. When they've faded, change the head.
The bristles are splayed or flattened
Look at the head from the side. If the bristles bend outwards past the edge of the head, or look squashed flat, replace it. This is the sign the 2019 study pointed to as most important.
It smells or looks discoloured
Philips and Expert Reviews both list smell and discolouration as reasons to change early. If cleaning the head doesn't fix it, replace it. Our guide on how to clean and look after your electric toothbrush covers the weekly clean that prevents this.
Your teeth don't feel as clean
Philips mentions this too. It's subjective, but if you notice that smooth feeling has gone after brushing, check the head.
Your brush reminds you
Some smarter brushes track head age for you. Tech Advisor explains that on the Oral-B iO Series 4, the mode button glows yellow when the head has been in use for about three months. You reset it by holding the mode button for two seconds, or through the Oral-B app if your brush is connected. The iO manual also describes a head replacement reminder on models with a display. Philips' Sonicare BrushSync heads work in a similar way: Currys says compatible handles remind you when to change, and the blue bristles turn white.
Not every brush has this. The Vitality Pro doesn't, and on simpler iO models you should check your manual. If yours doesn't, set a phone reminder.
Things that wear heads out faster
- Pressing too hard. The iO manual says that if bristles splay before the colour fades, you may be using too much pressure. A brush with a pressure sensor, such as the Oral-B iO3, helps you learn a lighter touch. See what a pressure sensor does.
- Braces. Brackets and wires snag the bristles. Currys lists braces as a reason heads wear sooner.
- Brushing more than twice a day. More brushing means more wear.
- Scrubbing technique. With an oscillating head, you guide it slowly from tooth to tooth rather than scrubbing. Our guide on how to brush properly with an electric toothbrush explains.
- Whitening or abrasive pastes. We haven't found good data on this, so treat it as a possibility rather than a fact, but a gritty paste plus heavy pressure is unlikely to help bristle life.
Should you change your head after being ill?
Sources disagree. Expert Reviews says you should replace your head after an illness, though it doesn't cite evidence. Currys says you don't normally need to replace it automatically after an ordinary illness. The ADA's toothbrush page doesn't recommend it either way.
We couldn't find solid research showing that an old head re-infects you with the same cold or flu. Our view is that it isn't essential after a common cold, but it costs a few pounds and some people feel better doing it. It makes more sense after something like a stomach bug, or if the head has been near other people's in a shared cup. If you have a weakened immune system, ask your dentist or doctor.
Can you make a brush head last longer?
Expert Reviews says no, and we agree. You can stop a head getting dirty or smelly before three months by rinsing and drying it, but you can't reverse bristle wear. Brushing with a lighter touch is the only thing that slows the wear itself.
Please don't share heads to save money. The ADA and Philips both say toothbrushes shouldn't be shared.
Which head fits your brush?
Oral-B has two head families that don't swap. iO handles only take iO heads, and the older round-head handles (Vitality, Pro and similar) only take the classic heads. Oral-B's iO head page says the heads are designed exclusively for iO handles.
| Your brush | Head type | Heads we sell |
|---|---|---|
| Oral-B Vitality Pro | Classic Oral-B round head | Pro Precision Clean, 12 pack |
| Oral-B iO2 and iO2 Night Black | Oral-B iO | iO Ultimate Clean, 4 or 8 pack |
| Oral-B iO2 Duo | Oral-B iO | iO Ultimate Clean, 8 pack covers two people for a year |
| Oral-B iO3 | Oral-B iO | iO Ultimate Clean, 4 or 8 pack |
For a full list of heads and handles, see which Oral-B brush head fits my toothbrush.
Three-year running cost
Changing every three months means four heads a year, or 12 over three years. Here's what that costs per person at our prices at the time of writing. Prices change, so check the product pages.
| Head | Pack and price | Per head | Per year (4 heads) | Three years (12 heads) |
|---|---|---|---|---|
| Oral-B Pro Precision Clean | 12 pack, £23.91 | About £1.99 | About £7.97 | £23.91 (one pack) |
| Oral-B iO Ultimate Clean | 4 pack, £21.41 | About £5.35 | £21.41 | £64.23 (three 4 packs) |
| Oral-B iO Ultimate Clean | 8 pack, £31.27 | About £3.91 | About £15.64 | £52.68 (one 8 pack plus one 4 pack) |
A few things stand out. The Vitality Pro is very cheap to run, at under £8 a year in heads. iO heads cost more, but buying the 8 pack rather than 4 packs saves about £11.55 over three years. For an iO2 Duo household, two people need 24 heads over three years, which is three 8 packs at £93.81 in total.
If you're still choosing a brush, running costs are part of the decision. Our guides to the best electric toothbrush under £60 and Vitality Pro vs iO2 include them.
If you change heads every two months instead because you wear them faster, multiply the yearly cost by 1.5. If you stretch to four months, as the ADA's upper limit allows, multiply by 0.75. Our advice is to let the bristles decide, not the budget.
Do electric heads and manual brushes follow the same rule?
Yes, broadly. The ADA's three to four month advice covers toothbrushes in general, and Philips says the same three months applies whether you're buying a new manual brush or a new electric head. Oral-B gives the same interval for its own heads.
There are a couple of differences worth knowing. An electric head moves thousands of times a minute, so the bristles do a lot more work per brush than a manual one, even though you're pressing more lightly. On the other hand, people often press harder with a manual brush, which is the main thing that splays bristles. In practice the two balance out roughly, which is why the advice ends up the same.
The bigger difference is how easy it is to forget. A manual brush is cheap and sits in a cup, so people replace it when it looks tatty. An electric head clicks onto an expensive handle, and the whole thing looks the same week after week, so it's easy to keep using a head for six months or more without noticing. That's where indicator bristles and app reminders earn their keep.
If you're weighing up the two types of brush in the first place, our article on electric or manual toothbrushes looks at what matters most, and sonic vs oscillating brushes explains the two kinds of electric head.
Who should change when
Most adults brushing twice a day
Every three months, or when the indicator bristles have faded, whichever comes first.
Heavy brushers
If your heads look splayed after six to eight weeks, change them then, and work on pressure. A brush with a pressure sensor is worth considering.
Children
Children often chew their brushes. Check the head every few weeks and replace it when it's chewed or splayed, even if it hasn't been three months.
Braces wearers
Expect to replace heads more often, and check them every few weeks. Ask your orthodontist whether they recommend a particular head.
Couples and families sharing a charger
Give everyone their own colour ring or head colour and change everyone's on the same day, so nobody loses track. Write the date somewhere obvious.
Tips for remembering
- Change heads at the start of each season: early March, June, September and December.
- Set a recurring phone reminder every 13 weeks.
- Keep the next head in the bathroom cabinet so you don't put it off.
- If your brush has a head reminder, reset it each time you fit a new head, or the timing drifts.
- Buy multipacks. You're more likely to change on time when the spare is already there.
Common problems
My heads splay after a few weeks
That usually means too much pressure. Hold the brush lightly, let it do the work, and guide it rather than scrubbing. A pressure sensor light will tell you when you're overdoing it.
The indicator bristles haven't faded but it's been three months
Change it anyway. Oral-B's head page says to replace every three months or sooner if worn, so the colour is a guide to wear rather than permission to keep going.
My iO button is glowing yellow
On the iO Series 4, Tech Advisor says that's the head replacement reminder. Fit a new head and hold the mode button for two seconds to reset it, or reset it in the Oral-B app.
A new head doesn't fit
Check you've got the right family. iO heads only fit iO handles, and classic Oral-B heads won't fit iO. If it's the right type, clean the shaft in case dried toothpaste is in the way.
The head smells before three months
Take it off and rinse inside it weekly, and let it dry in the open. If the smell is still there after cleaning, replace it.
Our verdict
Every three months is the right default, and it's what Oral-B, Philips and the ADA all recommend. But the research we found points more at the state of the bristles than the date on the calendar. If your heads splay early, change them early and look at your brushing pressure. If they look fine at three months, change them anyway; it's cheap insurance.
The cost is smaller than people expect. Classic Oral-B heads work out under £2 each in a 12 pack, and iO heads under £4 each in the 8 pack at our current prices. That's a few pounds a quarter for a brush that does its job properly.
Frequently asked questions
How often should you change an electric toothbrush head?
About every three months. Oral-B, Philips and Expert Reviews all say three months, and the American Dental Association says three to four months. Change it sooner if the bristles are splayed, frayed or discoloured.
How do I know when to replace my Oral-B brush head?
Look at the indicator bristles. On Oral-B heads they fade as the head wears, and Oral-B's iO head page says they fade from blue to white. Also replace it if the bristles splay outwards or it's been three months.
Is it bad to use the same toothbrush head for 6 months?
It's not recommended. Research on manual brushes found that more worn bristles were linked to more plaque, and every manufacturer and dental body we checked says to replace within three to four months. A six-month-old head is very likely splayed.
Do you need to change your toothbrush after being sick?
Sources disagree. Expert Reviews says replace it after illness, while Currys says you don't normally need to after an ordinary illness. We found no strong research either way, so it's a personal choice, though cheap to do.
Does the NHS say to change your toothbrush every 3 months?
Philips and Currys both say the NHS recommends three months, and Philips links to NHS Devon guidance. The main NHS page on keeping teeth clean doesn't give a replacement interval, so it's local NHS advice rather than a headline national statement.
Why do my toothbrush heads wear out so fast?
The most common cause is pressing too hard. The Oral-B iO manual says bristles splaying before the colour fades suggests too much pressure. Braces, brushing more than twice a day and scrubbing technique also shorten head life.
What does the yellow light on my Oral-B iO mean?
On the iO Series 4, Tech Advisor says a yellow mode button means the head has been in use for around three months and needs replacing. Hold the mode button for two seconds after fitting a new head to reset it.
Can I use iO brush heads on an older Oral-B toothbrush?
No. Oral-B says iO heads are designed exclusively for iO handles, and older Vitality, Pro and Genius handles only take classic Oral-B heads. The two systems don't swap.
Can two people share an electric toothbrush handle?
Yes, as long as each person has their own head. Never share the head itself; the ADA and Philips both say toothbrushes shouldn't be shared. Use coloured rings to tell heads apart.
How much do replacement Oral-B heads cost?
At our prices at the time of writing, Oral-B Pro Precision Clean heads work out at about £1.99 each in a 12 pack, and iO Ultimate Clean heads about £3.91 each in an 8 pack or £5.35 each in a 4 pack. Prices change, so check the product pages.
Do worn bristles really clean less well?
A little. A 2019 study of manual brushes found a weak link between bristle wear and plaque, with the biggest difference just under the threshold dentists treat as clinically meaningful. The authors recommended replacing brushes once the outer bristles start to splay.
Can I clean a brush head to make it last longer?
Cleaning keeps a head hygienic, but it can't undo bristle wear, so it won't extend its useful life. Expert Reviews says it isn't possible to extend it beyond the normal replacement point.
Sources
- Van Leeuwen et al. (2019), Toothbrush wear in relation to toothbrushing effectiveness, International Journal of Dental Hygiene
- TePe: How well does a worn toothbrush clean the teeth? (summary of Rosema et al. 2013)
- Oral-B UK: iO Ultimate Clean refill heads
- Oral-B iO instruction manual (brush heads)
- American Dental Association: Toothbrushes
- Philips UK: How to look after your toothbrush
- Expert Reviews: How often should you change an electric toothbrush head?
- Currys: How often to replace your brush head
- Tech Advisor: The button on your Oral-B iO is yellow, here's how to fix it
- NHS: How to keep your teeth clean
