If you wear braces or clear aligners and have noticed your breath isn’t as fresh as it used to be, you’re not imagining it. A new study comparing the two kinds of orthodontic treatment found a real difference in bad breath between them — but the more useful finding is why the difference shows up, and what that means for keeping your breath fresh while your teeth are being straightened.

What the researchers found

The study, “Orthodontic Appliance Type and Oral Malodor Burden,” was published in the journal Dentistry Journal in April 2026. It was a cross-sectional comparison of 184 people aged 15 to 35, split into three groups: 62 wearing clear aligners, 64 wearing fixed braces, and 58 untreated controls with no orthodontic appliance.

On the surface, the appliance seemed to matter. People in fixed braces had a higher unadjusted oral-malodor burden — measured both by an examiner smelling the breath (the organoleptic score) and by a halitosis quality-of-life questionnaire — than aligner wearers or the untreated group. In other words, the braces group, on average, had more noticeable bad breath and reported it bothering them more.

But the researchers then adjusted for the things going on inside each participant’s mouth, and the picture changed. Once they accounted for tongue coating, dental plaque, and salivary flow, the type of appliance no longer stood out as an independent driver of bad breath. What did stand out were three familiar culprits: more tongue coating, more plaque, and lower saliva flow were each linked to worse breath, regardless of which appliance — if any — a person wore.

The authors’ takeaway is careful and worth repeating: appliance type is best understood as a contextual factor that creates plaque-trapping conditions, not as a direct cause of bad breath on its own. Fixed braces have brackets, wires, and bands that are harder to clean around, so they tend to hold more plaque and debris — and that, not the metal itself, is what feeds the odor-producing bacteria.

What it means for your breath

A few caveats first. This was a cross-sectional study — a single snapshot in time — so it can show associations but cannot prove that one thing causes another, and it cannot tell us how breath changes over the course of treatment. The participants were teenagers and younger adults, and the groups were modest in size. Treat it as a useful clue, not the last word.

That said, the practical message lines up neatly with everything we already know about what causes bad breath. Odor in the mouth comes overwhelmingly from bacteria breaking down trapped food and debris, especially on the tongue and along the gumline. Braces and aligners don’t change that chemistry — they just make it easier for plaque and coating to build up if your cleaning routine doesn’t keep pace.

So if you’re in treatment and worried about your breath, the fixes are the ordinary ones, done a little more diligently:

  • Clean thoroughly around brackets and wires, and floss with a threader or interdental brush to reach what a regular brush misses.
  • Don’t skip your tongue — coating on the back of the tongue is one of the biggest sources of odor. A simple tongue cleaner helps.
  • Keep saliva flowing. Aligner wearers in particular can get dry mouth from keeping trays in for long stretches, and a dry mouth smells worse — so stay hydrated and rinse with water after meals before re-seating aligners.

Neither braces nor aligners doom you to bad breath. The study is a reminder that the appliance is just the setting; your daily cleaning is what actually decides how your breath smells.

Sources

  • Orthodontic Appliance Type and Oral Malodor Burden: Cross-Sectional Comparison of Clear Aligners, Fixed Braces, and Untreated Controls — Dentistry Journal, 14(4):225, April 2026. DOI: 10.3390/dj14040225. https://doi.org/10.3390/dj14040225

This article is for general information and is not a substitute for professional dental or medical advice.