TL;DR: Thirty days, two brushes, one bathroom in Rotterdam. I put the Oral-B iO Series 9 and the Pro 3 3900 through daily use to see what the extra €130 actually buys you. Quick answer: the round head still cleans harder than any sonic I've owned, and the pressure sensor is the feature that changes brushing habits. Check current Oral-B pricing →
01Why I switched from a sonic brush
I had a Philips 5100 for three years. Good brush. My hygienist in Utrecht kept flagging plaque on my lower molars every visit anyway. She asked what I was using. When I told her, she shrugged and said, "Try a round head."
That is the entire origin of this review.
I bought the Oral-B iO Series 9 Value Pack from Coolblue at €211 (down from €219) and, out of curiosity, the Pro 3 3900 at €77 to see how much of the cleaning quality lives in the round head alone versus the fancy iO motor. Both have the round oscillating head. Only the iO9 has the magnetic drive, the colour OLED, the pressure ring, and the app.
How we tested these brushes
02Week 1: the pressure sensor changes everything
Day 1, first brush. The light ring around the base of the iO9 handle went red within 20 seconds. I was pressing too hard on my lower left molars — exactly where the hygienist keeps finding plaque. My old sonic brush had no way of telling me this.
Green means you're brushing right. Red means back off. White means you're barely making contact.
By day 4 the red light stopped triggering. Something in my hand had adjusted. The Times of India review of the iO9 called this "muscle memory that dental professionals spend years trying to teach." Cheesy phrasing, but accurate.
The Pro 3 3900 has a pressure sensor too. It flashes a red LED strip along the neck of the brush. Same idea, less visible when the brush is in your mouth. It still worked. I retrained the same molar habit within a week using the cheaper brush.
03Week 2–3: what the extra €130 buys
Here is the honest split. The iO Series 9 adds:
- Magnetic drive motor. Runs at about 64 dB, distinctly quieter than the Pro 3's mechanical whir at around 74 dB. My partner noticed on day one.
- Colour OLED display. Shows mode, battery percentage, and a smiley when you hit two minutes. Sounds silly. Made me brush the full two minutes more consistently.
- Seven modes. I used two: Daily Clean and Sensitive.
- App with 16-zone tracking. Genuinely useful for the first fortnight. I found out I was under-brushing my upper lingual surfaces. Then I stopped opening the app.
- Charging travel case. Actually holds a full charge.
The Pro 3 3900 gives you:
- Same round head, same oscillating motion
- Two-minute timer with 30-second quadrant pacer
- Basic pressure sensor
- Three modes — Daily Clean, Sensitive, Whitening
- 12–14 day battery life
Both cleaned my teeth to the same standard by the hygienist's chair at my three-week check. She could not tell which brush I had used that morning. She could tell my technique had improved.
That is the review in one line. The round head cleans. The pressure feedback fixes technique. Everything else is refinement.
04Product picks for NL buyers
| Model | Price (EUR, NL) | Rating | Best for |
|---|---|---|---|
| Oral-B iO Series 9 | €211 (Coolblue Value Pack) | 4.6/5 | Tech-focused users, uneven brushers who want app coaching |
| Oral-B iO Series 6 | €149–169 | 4.5/5 | Best value iO — display and tracking without flagship cost |
| Oral-B iO Series 3 | €79–99 | 4.4/5 | Entry to the iO magnetic drive, no app, no display |
| Oral-B Pro 3 3900 | €77 (Coolblue duo) | 4.5/5 | Best budget pick — same round head, no smart stuff |
Prices sampled from Coolblue, Bol.com and MediaMarkt on 16 September 2026. Black Friday historically drops the iO9 by another 30–40% around 27 November — worth waiting if you can.
Oral-B iO Series 9 — the brush this review is built around
Magnetic drive, colour display, three-colour pressure ring and the charging travel case. The Pro 3 3900 duo sits in the same range if the budget is tighter.
🇳🇱 Prices sampled from Coolblue, Bol.com and MediaMarkt on 16 September 2026 — NL Black Friday falls on 27 November and historically drops flagship models 40–55%. Affiliate link — we may earn a commission at no extra cost to you.
05Battery: solid, not exceptional
Oral-B rates the iO9 at "more than two weeks." Real world at month one with twice-daily brushing: 12 days. My old Philips lasted 18. If you travel a lot, Sonicare still wins on battery.
The magnetic base charges the iO9 in about three hours. The travel case adds another full charge. For a two-week trip I would take the charger anyway. The Pro 3 hit 14 days on my testing and charges via a standard Braun base. It just works.
06What I would not do
✓Worth the money
- iO Series 9 at the €189–211 sale range, not the €329 MSRP
- iO Series 6 if you want the display without the flagship premium
- Pro 3 3900 duo at €77 if you already brush well
- Genuine Oral-B replacement heads — fit is consistent
–Skip these
- iO Series 10 at €429. The only real upgrade is the smart charger with LED zone display, and it's 10–12% quieter. Not €200 quieter.
- iO2. Different motor, missing the pressure sensor on some SKUs, and the price advantage disappears the moment the iO3 goes on sale.
- Third-party iO heads — fit is inconsistent
07Replacement head reality
iO-specific heads run €7–9 each on Bol.com, four-pack for €26–32. Standard Oral-B heads — compatible with the Pro 3, Vitality and Genius lines — run €4–5 each. Over five years of quarterly replacement, expect around €150 more on iO heads.
Frequently asked questions
Is the iO9 worth it over the Pro 3? If the price gap is under €100, yes — the quieter motor and pressure ring genuinely improve daily use. Above a €130 gap, buy the Pro 3 and put the difference into a proper flossing habit.
Does the app actually help? For two to four weeks, yes. Then most people stop opening it. That is not a failure — it did its job.
Round head vs oval sonic — which is better? Independent research (van der Sluijs et al., 2023, 32 studies, 2,805 participants) gives oscillating-rotating a small edge on plaque and bleeding indices. The authors call it "a very small clinical relevant beneficial effect." Small but real. Round head wins on crowded teeth and braces. Sonic wins on receding gums.
Where do I buy in the Netherlands? Coolblue for best price and next-day delivery. Bol.com for the widest selection. MediaMarkt for in-store pickup.
What about Prime Day and Black Friday? NL Black Friday 2026 falls on 27 November. Historically the iO9 drops to €169–189 and the iO10 to €249. Track prices from mid-October to avoid inflated "was" prices.
08The verdict
The Oral-B iO Series 9 is the best Oral-B I have used. It is not five times better than the Pro 3 3900 despite costing three times as much. If you already brush well and just want a solid electric, buy the Pro 3. If you want a coach on your countertop for the first month and then a very quiet, very smooth brush after that, the iO9 earns its price at the €189–211 sale range — not the €329 MSRP.
Three years of hygienist reminders did not fix my technique. A red light on a handle did it in four days. That is what you're actually buying.
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