Philips Sonicare DiamondClean Smart 9400 Review: A Stand-Out Toothbrush That Comes At A Cost
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If you are serious about your oral health, chances are you have come across the Philips Sonicare DiamondClean Smart 9400. It sits right at the premium end of the best electric toothbrush market, promising smart features, superior cleaning and a polished user experience. But with a price tag that makes many people pause, the big question is simple: does it genuinely deliver enough to justify the cost?
This in-depth review explores everything you need to know, from daily performance to long term usability, so you can decide whether this high end toothbrush deserves a place in your bathroom.
This article contains affiliate links; however, all the opinions are my genuine thoughts after trialling the toothbrush both at home and when travelling - Owen Gough
Last Updated on 5th May 2026
Philips Sonicare DiamondClean Smart 9400
I love Philips range of electric toothbrushes because of the sonic pulse technology and sturdy build quality, but all the best features from the brand are epitomised in the Sonicare DiamondClean Smart 9400. Sitting at the top of the pile (just below the DiamondClean 9900 Prestige model) it offers intelligent AI smartphone integration, a huge battery and a host of useful features to level up your dental health.
In Summary
From my perspective, this brush is one of the best overall electric toothbrushes and appeals to almost any user, no matter what dental issues you may suffer from. With AI smarts, a sleek design and purpose-built tech to make cleaning your teeth easier and more comfortable. The high price tag is definitely a barrier for many, but it offers far too much value in my opinion.
★★★★★
Best for: Most people looking to elevate their dental care routine
Key feature: AI smartphone integration
Battery life: 28-31 days (real-world testing)
Pros
Sonic pulse technology that’s gentle on teeth and gums
Travel case included
Smartphone app integration that’s easy to use
Great battery life
Long-lasting battery
Glass wireless charging port
Four cleaning modes at three intensities
Sleek design
Cons
Expensive
Minimalist design might be off-putting to some
Cleaning modes can feel quite intense at the more vigorous modes
App usage might be too much tech if you’re not used to using your smartphone while cleaning
Who Reviewed This?
Reviewed by Dr Zaeem Jafri (GDC-registered dentist) & Owen (product reviewer for major UK publications).
We combine clinical dental expertise with real-world product testing. Every toothbrush we review is used daily in a home setting for a minimum of 3 weeks by Owen, who has tested hundreds of products for some of the biggest lifestyle and health magazines in the country. In his reviews, he’s looking out for cost, cleaning power, tech features and usability, and if this lines up with Dr Jafri’s clinical opinions.
How We Tested The Philips SoniCare DiamondClean Smart 9400
We tested the Philips SoniCare DiamondClean Smart 9400 over 3 weeks, brushing twice daily with a standard Colgate cleaning toothpaste.
We assessed:
Plaque removal
Gum comfort
Battery life
Noise levels
Ease of use
App usefulness
Design and Ergonomics
At first glance, the DiamondClean Smart 9400 looks every bit like a luxury product, and I loved opening it and feeling the smooth design. The handle is slim, handsome and finished in matte tones that feel more like a premium gadget than a bathroom essential. It is available in a handful of elegant colours, giving it a subtle edge over more clinical looking competitors.
In the hand, it feels balanced and comfortable. The weight distribution is spot on, making it easy to manoeuvre around my mouth without strain. The single button interface keeps things minimal, while the LED indicators are bright without being distracting.
The charging glass and travel case add to the premium feel. The glass charger doubles as a rinsing cup, which is a clever touch that blends practicality with aesthetics.
Cleaning Performance
Ultimately, design only matters so much. Cleaning performance is where this toothbrush really earns its reputation.
Using sonic technology, the brush delivers up to 62,000 brush movements per minute at an intense vibration, lifting plaque from between your gums and the surface of your teeth, leaving your mouth feeling clean and smooth.
Plaque removal is excellent. After just a few uses, my teeth feel smoother and cleaner, especially in hard to reach areas. Over time, I even found brighter teeth thanks to the polishing action of the brush heads.
It is particularly effective along the gumline, where plaque tends to build up most. The precision of the brush combined with its speed gives it a clear advantage over many mid range electric models.
Key Features
The DiamondClean Smart 9400 is packed with features designed to elevate your brushing routine:
Multiple cleaning modes including Clean, White Plus, Gum Health and Deep Clean
Three intensity settings to tailor your brushing experience
Smart sensor technology that tracks brushing habits
Automatic mode pairing with compatible brush heads
Real time feedback via the companion app
Each feature feels purposeful rather than gimmicky. I often find that multiple cleaning modes feel roughly the same, but here, with the addition of intensity customisation, you can play around with the settings to get a mode that feels perfect for you, and the brush will remember the settings you enjoy for future use.
Gum Comfort
One of the standout qualities of this toothbrush is how gentle it can be when needed.
Despite its powerful motor, the DiamondClean Smart 9400 includes a pressure sensor that alerts you if you are brushing too hard, warning you with a gentle nudge and a light to ease off. This is particularly valuable for people with sensitive gums or those prone to gum recession, and a feature I find particularly useful, as I have a habit of pressing too hard.
The Gum Health mode is designed specifically to improve gum condition over time using a gentler brushing patterns while still maintaining effective plaque removal.
For most users, the balance between power and comfort is excellent. You get a thorough clean without the harshness that some high powered brushes can bring.
Noise Level
Electric toothbrush noise is often overlooked until you are standing in front of the mirror at 6am, trying not to wake up the rest of the house.
The DiamondClean Smart 9400 is relatively quiet for a sonic toothbrush. It produces a soft humming sound rather than a harsh buzz, which while isn’t silent, is far less intrusive than many older electric models.
This makes it a better option for shared households or anyone who prefers a less jarring start to their day.
Travel-Friendly Features
For frequent travellers, this toothbrush offers a thoughtful set of features.
The included travel case is sturdy and compact, with a built in USB charging option. This means you can charge your toothbrush on the go without needing to pack a bulky charging base.
The case also protects the handle and brush heads effectively, keeping everything hygienic during travel.
It is worth noting that the handle itself is slightly larger than some entry level brushes, but this is a small trade off for the added functionality.
Once again, I’ll also highlight the glass charging case, which keeps the device clean and elevates from the sink side, charges it and doubles up as a rinsing cup, which are all excellent features to enjoy while travelling.
Battery Life
Battery performance is another area where this toothbrush shines.
On a full charge, the DiamondClean Smart 9400 can last up to two weeks with regular use. This makes it ideal for travel and reduces the need for frequent charging.
The charging glass is simple to use. Just place the handle inside and it begins charging automatically. The LED indicator provides a clear view of battery status.
Compared to many competitors, the battery life is both reliable and convenient.
Ease of Use
Despite its advanced features, the DiamondClean Smart 9400 remains easy to use.
The controls are intuitive, with a single button to power the device and cycle through modes. The handle remembers your last used setting, so you do not need to adjust it every time. It’s a downside to many high-end brushes, that it becomes overly complicated with features and buttons, but once I got it charged up and used it regularly, I didn’t have any headaches using the features.
BrushSync technology automatically selects the optimal mode based on the brush head you attach. This takes the guesswork out of choosing settings and ensures you get the best performance.
Even if you choose not to use the app, the toothbrush functions perfectly well as a standalone device.
App Experience
The companion app adds an extra layer of functionality for those who want it.
It provides real time feedback as you brush, highlighting areas you may have missed and offering tips for improvement. Over time, it builds a record of your brushing habits, helping you track progress, giving you personalised coaching tips to improve your brushing over its lifetime.
For beginners or those improving their oral care routine, this can be genuinely useful. However, more experienced users may find it unnecessary after a while.
The app connects easily via Bluetooth and is generally stable, though like many smart features, it depends on consistent use to deliver value.
Price
There’s no getting around it. This is an expensive toothbrush.
The DiamondClean Smart 9400 sits firmly in the premium category, often costing significantly more than standard electric toothbrushes at £200. Replacement brush heads are also on the higher end of the price spectrum.
While the features and performance justify some of the cost, it is still a considerable investment for a daily essential.
Who Should Buy This?
This toothbrush is best suited for people who want a high end oral care experience and are willing to pay for it.
It’s a great choice for those with specific dental concerns such as gum sensitivity or plaque build up. It is also ideal for users who appreciate smart features and detailed feedback on their brushing habits.
If you value design, performance and advanced functionality in equal measure, this model will likely meet your expectations.
Electric Toothbrush Alternatives
If the price feels steep, there are several alternatives worth considering.
The Oral B iO10 offers a different brushing technology with oscillating and rotating action, along with its own smart features. It provides excellent cleaning performance at a slightly lower price point depending on the model.
The standard Philips Sonicare ProtectiveClean range is another strong option at a quarter of the price. It delivers reliable sonic cleaning without many of the advanced features, making it more affordable.
For those on a tighter budget, entry level electric toothbrushes can still offer a significant improvement over manual brushing, even if they lack premium extras.
What Makes It Different?
What sets the DiamondClean Smart 9400 apart is the combination of performance, design and smart technology.
Many toothbrushes excel in one or two areas. This model manages to bring together powerful cleaning, user friendly features and a refined aesthetic in a single package.
The smart sensors and app integration add a personalised element that few competitors match at this level. At the same time, it does not compromise on core performance, which remains its strongest asset.
Is It Worth The Price?
The answer depends largely on your priorities.
If you are looking for the best possible cleaning performance with added smart features and premium design, then yes, it is worth the investment. It delivers a noticeable upgrade in both experience and results.
However, if you simply want a reliable electric toothbrush that gets the job done, there are more affordable options that will still meet your needs.
In short, this is a luxury product that performs like one. The value is there, but only if you are willing to pay for the extras.
FAQs
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Most brush heads should be replaced every three months. The BrushSync feature will notify you when it is time for a change.
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Yes. The adjustable intensity settings and Gum Health mode make it suitable for users with sensitivity.
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No. The toothbrush works perfectly well without the app, though you may miss out on some of the advanced feedback features.
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It is designed primarily for adults, though older children may be able to use it under supervision.
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It helps remove surface stains, which can make teeth appear whiter over time. It is not a substitute for professional whitening treatments.
What Do You Think?
If you’ve got an Philips toothbrush, we would love to know what you think of it. Have you enjoyed using it, have you had any problems?
Disagree with something in our review?
Let us know in the comments below!
If you are serious about your oral health, chances are you have come across the Philips Sonicare DiamondClean Smart 9400. It sits right at the premium end of the best electric toothbrush market, promising smart features, superior cleaning and a polished user experience. But with a price tag that makes many people pause, the big question is simple: does it genuinely deliver enough to justify the cost?
This in-depth review explores everything you need to know, from daily performance to long term usability, so you can decide whether this high end toothbrush deserves a place in your bathroom.