Feno vs Autobrush vs Y-Brush: U-shaped toothbrushes compared

Fit is where U-shaped brushes have historically failed. When researchers tested a 10-second auto-cleaning device against uninstructed manual brushing, full-mouth plaque reduction was about 11% versus 31%, and when they checked the device against dental casts, at most two of its four bristle rows touched the teeth. Their conclusion named the fix: better bristle alignment and assorted sizes to cover different jaw shapes (Clin Oral Investig, 2021).

Feno ships seven TrueFit Mouthpiece sizes. You scan your mouth in the Feno app after purchase, we match you to the closest size, and your first two size exchanges are free. It isn't a custom mold. It's the closest of seven pre-made sizes.

Autobrush offers three adult sizes (small, regular and XL) plus three kids' sizes, with a Perfect Fit Promise to swap a poor fit for free. Y-Brush offers two sizes: M for ages 12 and up, S for children 4 to 12. One adult size for every adult arch is the pattern the 2021 study warned about, and it's why Y-Brush scores lowest here.

A mouthpiece brush can only clean the surfaces its bristles actually touch. A 2023 pilot study of Y-Brush measured exactly that: in 95% of participants the device was too short to fully cover the second molars, and on about 31% of teeth the bristles never reached the gumline (Clin Oral Investig, 2023). The same study found that 15 seconds per jaw produced plaque reduction comparable to manual brushing, so the concept can work when the bristles reach.

Feno's TrueFit Mouthpiece carries about 18,000 ultra-soft nylon bristles fused to a flexible plate that adapts to your arch, and it brushes the upper and lower teeth at the same time. Your FitKit scan captures your teeth from front to back, so the size you receive accounts for your back molars. You still move it in slow circles while it runs, and you still floss. Feno cleans the front, back and top of each tooth. Only floss cleans between them.

Y-Brush's Clean240 head packs 35,000 nylon filaments angled at 45 degrees, more filaments than Feno, but it covers one arch at a time: top teeth, then bottom. Autobrush uses a U-shaped nylon head with an added fourth row of soft silicone bristles, and its own instructions say it's not hands-free: you move it side to side and in figure eights to reach the back teeth. Both are credible designs; Y-Brush edges Autobrush on filament count and bristle angle. Feno scores highest because it combines both arches at once with a sized, flexible plate.

The ADA's guidance is two minutes, twice a day, with a soft-bristled brush and fluoride toothpaste, and that evidence base was built on brushes that clean one area at a time. We've written about why simultaneous cleaning changes that math in Does Brushing Longer Clean Your Teeth Better? Time matters as a stand-in for coverage.

Feno runs one 20-second cycle that delivers 250 strokes across both arches, using gentle translational movements rather than vibration, with intensity you can adjust in the app or with the buttons on the Smarthandle. One cycle, one routine, the same every time. That consistency is the case for Feno, not a claim that 20 seconds works for every brush.

Y-Brush Ultra cleans in 20 seconds total with the Clean240 head, one arch and then the other, and it also accepts a standard sonic head for a conventional two-minute brush. Remember the 2023 pilot: 5 seconds per jaw wasn't enough and 15 seconds per jaw was comparable to manual brushing, so your time choice matters more with Y-Brush. Autobrush asks for 30 seconds, with light-coded 30, 60 and 90 second modes, plus hand motion throughout. Flexible, but less of a fixed routine.

A timer tells you how long you brushed. It can't tell you what you missed. That gap is most of what we mean by smart in What Does a Smart Toothbrush Actually Do?

The Feno Smarthandle sends your scan, brush and streak data to the Feno app. The app's scanner captures images of your gumline, tooth surfaces and tongue so you can see potential areas of concern and track changes over time. These are insights, not diagnoses, and no home device replaces a dental exam. The scanner runs only while you brush, with a Trust light and a separate privacy chip, and the brush works fully without the app or Wi-Fi.

Autobrush's guidance is a set of LED timer colors (green for 30 seconds, blue for 60, red for 90) and three cleaning modes. Y-Brush Ultra offers six sonic modes. Neither product page we read lists an app, a scan or a brushing history. If you don't want an app in your bathroom, that's a point in their favor. As a tracking criterion, it's one of the widest gaps on the board. Autobrush edges Y-Brush only because its timer lights pace the 30 seconds for you.

This is the criterion we lose, and we'd rather say it ourselves. Autobrush's U-shaped Toothbrush Series carries the ADA Seal of Acceptance. In the ADA's words, the Council on Scientific Affairs found the product "is safe and has shown efficacy in removing plaque and helping to prevent and reduce gingivitis, when used as directed." Feno has no ADA Seal. Y-Brush doesn't claim one either.

On published research, none of the three has a flattering record. Independent randomized trials of U-shaped and Y-shaped automatic brushes have mostly found less plaque removal than manual brushing. A 2020 crossover trial found one U-shaped automatic brush removed no more plaque than not brushing at all (Int J Environ Res Public Health, 2020). A 2024 trial found Y-Brush beat no brushing but trailed manual brushing at both 45 and 120 seconds (Clin Oral Investig, 2024). A 2025 study found a U-shaped electric brush removed less plaque than single- or triple-headed manual brushes, though users found it more comfortable (Int J Dent Hyg, 2025). None of those trials tested Feno or Autobrush.

Autobrush cites its own clinical studies as data on file; we didn't find them in a peer-reviewed journal, and most of those comparisons pit 30 seconds of Autobrush against two minutes of a manual brush. Y-Brush cites a 110-subject study against a sonic brush that we couldn't locate in PubMed. Feno has no published study. We report internal testing, and we don't call it proof. Autobrush wins because the Seal is an independent evaluation the other two can't match. Y-Brush edges Feno because outside researchers have at least tested it, even when the results were mixed.

Autobrush Sonic Pro lists at $89 and was on sale for $74 when we checked. Y-Brush Ultra is $99.99. Feno's Founder's Edition Bundle is $299 one-time, or $199 up front plus $19.99 a month on the subscription plan. On the price tag alone, Feno costs three to four times as much.

Replacement heads are closer than the sticker suggests. Autobrush's head subscription is $25 every two months. Y-Brush's Clean240 head is $29.99, or $24.99 every two months on its Ultra subscription. Feno's TrueFit Mouthpiece is $29, or $24.65 on subscription. The Feno bundle also includes three bottles of Feno Foam and a tongue scraper, and it's HSA/FSA eligible, as is Autobrush.

Warranty favors the rivals too: two years from Autobrush (lifetime while subscribed to heads), lifetime from Y-Brush with its refill program or one year otherwise, and 12 months from Feno once you register in the app. We priced Feno as a system with a scanner, an app and a sized mouthpiece. If all you want is a U-shaped brush, Autobrush is the value pick, and it isn't close.