Feno Smartbrush Review: The Worst Thing I've Ever Shoved in My Mouth

Gizmodo

25-05-2025

The Feno is supposed to brush all your teeth at once. But after using this "toothbrush" for three weeks, maybe just stick to your $5 manual brush.
Feno, the 'smart electric toothbrush,' promised to take a two-minute toothbrushing routine and bring it down to 30 or even 20 seconds by swabbing each of my teeth at once. The Feno Smartbrush makes brushing faster, but in exchange it requires you to shove an entire mouthpiece in your piehole twice a day just to cut down on a total of three minutes of brushing time. If there is one thing to take away from this review, it's that even if tech works, it doesn't necessarily mean it's better than what we already have.
The 'toothbrush' has been at the side of my bathroom sink for more than three weeks. It has technically saved me time. I would even go as far as to say it may do the job of a regular toothbrush with less time to get there. Still, given the choice, I would rather reach for my non-motorized, dentist-recommended toothbrush—if only because I know it works. After consulting with the companies and non-affiliated dentists, I'm more bemused that the Feno exists at all. This is a device that costs $300 for the 'Founder's Edition' bundle. The company recently said it would increase the price to $400, blaming tariffs for the rising cost. As the time of this publishing, that new price hasn't yet materialized. The box comes with three canisters of brand-specific Feno Foam toothpaste. After you run out, you'll need to spend $30 to get an extra three canisters. Feno also recommends replacing the mouthpiece every three months, costing another $30.
Feno Smartbrush
It may brush all your teeth for quicker cleans, but its too much of an unknown to recommend.
Pros Designed to brush at correct angle with dentist-recommended motion
Designed to brush at correct angle with dentist-recommended motion App is relatively easy to use
Cons Too uncomfortable versus regular toothbrush
Too uncomfortable versus regular toothbrush Requires app to operate
Requires app to operate Uses proprietary foam-based toothpaste
Uses proprietary foam-based toothpaste Price is 30x that of a toothbrush and toothpaste
My dentist gave me my last manual toothbrush for free. A tube of toothpaste was $5. Despite the price, the company behind the smart toothbrush has one compelling pitch. If people were honest with themselves, most folks do not do the recommended amount of brushing. I fit into that camp for most of my life, until the point I went to my dentist and found I needed to have multiple caps on my molars, requiring I spend a hefty chunk of change for the privilege of having my teeth ground down to nubs. Since then, I've become very sensitive to the state of my pearly whites. I try to do the full two minutes of brushing and floss every day, but the Feno is supposed to help by shortening the brushing time and helpfully counting you down with an on-screen timer.
My dentist was skeptical about the device's claims, especially whether it was offering proper back-and-forth brushing technique. The American Dental Association has a Seal of Acceptance tested by the organization for products that are recommended by dentists. Neither Feno's brush nor special toothpaste are on that list of products with the ADA seal. All I have to go on is Feno's own claim that it's doing what it needs to do to clean my teeth and remove plaque. For cleaning, the device makes use of pressure sensors alongside the mouthpiece's 18,000 bristles, which Feno claims can hit 250 strokes per tooth in 20 seconds. It's using a sweeping motion along the teeth, which dentists recommend when brushing, but there's no published science to say the Feno is particularly better than other, similar devices. Feno told me the company has scientific research pertaining to how effective the device is, but it's pending scientific review and won't be available until some unknown date.
Feno revels in Silicon Valley startups' worst habits. Every time you turn it on, the smart toothbrush bombards you with a QR code to download an app for all its controls, rather than including those on-device. The Feno toothbrush can incite the same gag reflex you know if you've ever played a contact sport requiring a mouth guard. The device is big enough that you have to open wide to fit the whole thing in at once. Brushing with the Feno is not an entirely passive experience, either. Feno's founder, Dr. Kenny Brown, told me his company recommends moving the brush side to side while the mouthpiece actuates.
On its highest settings, the Feno rattled my jaw and made my entire head shake like a marionette piloted by a mad puppeteer. With those speeds, I could feel the mouthpiece rubbing the inner cheek raw. At normal speeds, the Feno was uncomfortable but still usable without any pain. Feno also advises some gums may bleed if you haven't been doing proper brushing technique for too long, but I didn't find the bristles were any more abrasive to my gums than a regular toothbrush. The device running on default settings for 30 seconds seems engineered for most mouths.
The company claims its device works with regular toothpaste, but when I plastered some gel to the bristles and stuck it in my mouth, it resulted in a sludgy mess at the bottom of the mouthpiece that took far longer to clean than the typical quick rinse. The foam toothpaste doesn't leave your mouth full of the typical minty taste of fluoride and baking soda you normally associate with the feel of a clean mouth. As a point in favor of the Feno, that minty-fresh taste in your mouth isn't actually indicative of clean teeth, according to Dr. Edmond Hewlett, a professor at UCLA's School of Dentistry and a consumer advisor for the American Dental Association. Brown told me the company plans for updated toothpaste that adds a lingering minty taste in the mouth, as apparently I wasn't the only one who spoke up on that lack of 'clean' feeling.
Knowing my dentist appointments are near for even more fillings, the Feno would not only need to be good, but even better at cleaning my teeth than the typical electric brush. Even if I felt it may be hitting all my teeth, the device didn't leave me feeling clean, not least because I had no control over it.
Even if the Feno full-mouth toothbrush wasn't uncomfortable, wasn't expensive, didn't require an app, and worked well with regular toothpaste, it would still be hard to make any claim it results in better cleaning than your regular $7 toothbrush you buy from any local pharmacist. Using the smart toothbrush, you can't tell what's happening to your teeth. You can't tell if it's hitting all the nooks and crannies. That's going to be a concern when everybody's set of teeth is different. The Feno is supposedly designed so that all its bristles hit all different kinds of teeth at the correct 45-degree angle to the gums, but what really matters is if it adds anything to your brushing routine.
'The critical question of any device like this is if it's better than a toothbrush,' Hewlett told me. 'It's clear that using a toothbrush properly is one of the most effective things a person can do themselves to preserve their teeth.'