One disclosure before anything else: Evexia’s owner also owns Greco Gum, which competes with Underbrush. I’m not a neutral party here. With that on the table:
Underbrush had been showing up in every third video on my feed: the ex-chef founder, the “ordinary gum is plastic and you’re chewing it” hook, the promise that one little piece could remineralize your teeth. So I bought a few flavors and chewed them, most days, for about a month.
What Underbrush is, and who makes it
Underbrush comes from Nathan & Sons, a small brand started by a former chef, Nathan Mal, who reformulated gum after souring on what conventional gum is actually made of. It launched in early 2025 and went off like a rocket on TikTok. The pitch is sharp. Normal gum uses a synthetic, basically plastic, base; Underbrush uses a natural tree-resin base instead and adds hydroxyapatite, the mineral your tooth enamel is literally made of. It’s sugar-free, comes 18 pieces to a pack, and runs about $29.99, a little over twenty if you submit to the subscribe-and-save nudge. The flavors include Mastic Mint, Cinna-Mastic, Berry, and Tropic Twist.[8]
Credit where it’s due: the core instincts are good. A tree-resin base instead of polyvinyl acetate is a real, meaningful difference, and hydroxyapatite is a legitimate ingredient with genuine science behind it. This is not a cynical cash grab. Someone clearly cares about the formula. The trouble starts with what Nathan & Sons claims that formula does.
What’s in it
| Ingredient | What it's doing |
|---|---|
| Hydroxyapatite (nano + micro) | The headline mineral, the one enamel is made of. Real science behind it, mostly in toothpaste. |
| Natural resin base (chicle, mastic, spruce, myrrh, acacia, candelilla) | The plastic-free chew, and the best idea in the product. |
| Xylitol + erythritol | Sugar-free sweeteners. Xylitol is genuinely tooth-friendly, a real plus. |
| Zinc, magnesium, bentonite clay, terpene blend | The supporting cast and the 'clean label.' Minor players. |
That ingredient list is genuinely clean, and I have no complaints about it.[7] Two things are worth flagging, though.
First, the mastic. Yes, there’s mastic gum in the base and a whole “Mastic Mint” flavor, but don’t let that fool you into thinking this is a mastic gum. It’s a soft, sweet, flavored gum that happens to contain a little mastic resin. Hold that thought, because it matters by the end.
Second, and more telling, there’s a number missing. Underbrush tells you hydroxyapatite is in there. It will not tell you how much sits in each piece. For an ingredient whose entire pitch is dose-dependent remineralization, leaving off the dose is a strange choice, and it was the first thing that made me raise an eyebrow.
Does Underbrush gum work?
As a sugar-free chew that freshens breath and gets your saliva going, it works, obviously. As the enamel-rebuilding treatment the marketing implies, there is no good evidence that this gum does anything of the sort.
Hydroxyapatite itself has real science behind it. In toothpaste, it remineralizes early enamel about as well as fluoride under the right conditions, a genuine and repeated finding, even if the wider body of evidence is still short-term and not yet conclusive.[1] Head-to-head, hydroxyapatite and fluoride toothpaste have come out roughly even.[2] That much is legitimately good, and it’s the reason hydroxyapatite isn’t snake oil.
That evidence, though, is all for toothpaste. When a 2025 review went looking for clinical studies of hydroxyapatite in chewing gum specifically, it found exactly one: a small, niche experiment in which the plant-derived hydroxyapatite actually underperformed.[3] [4] That single study is the entire evidence base for the format Underbrush sells.
There is a remineralizing chewing gum with a real body of human evidence behind it, but it runs on a completely different ingredient: CPP-ACP, which you’ll see branded as “Recaldent,” not hydroxyapatite.[5] So when a hydroxyapatite gum leans on “remineralization science,” it’s quietly borrowing toothpaste studies for its own ingredient and gum studies for a different ingredient, and betting you won’t check.
The smoother-teeth effect is the same story. Plenty of the glowing reviews describe teeth feeling clean and slick after chewing, and I felt it too. But that’s what any sugar-free gum does. It’s the saliva and the xylitol, and you’d get the identical feeling from a pack of drugstore mint. None of it is evidence the hydroxyapatite did a thing.
To be fair, hydroxyapatite is safe. It’s the mineral your teeth are already made of, and regulators have looked hard at it and cleared it for oral care.[6] Nobody is getting hurt. Underbrush’s own site, to its credit, admits the gum won’t fix a cavity that has already formed. The problem was never safety, and it was never outright lying. It’s a real ingredient being asked to carry a promise the gum format simply hasn’t earned yet.
What it’s like to chew
This is where Underbrush wins some of me back. The chew is genuinely nice. That tree-resin base feels different, firmer and a little more “alive” than the slightly plastic snap of drugstore gum, which makes sense, given that it isn’t plastic. Mastic Mint was my favorite, though I’ll cop to a bias toward anything with mastic in it.
The catch is the one every reviewer lands on, and I’m no exception: the flavor disappears fast. It doesn’t fade gently over ten minutes. It’s gone in about a minute, and after that you’re chewing a pleasant, nearly flavorless resin. The pieces are small, and a couple in one pack came out hard and slightly crumbly, which matches the quality-control gripes you’ll find if you go digging. My teeth did feel clean and smooth afterward, and you already know why that isn’t the flex it sounds like.
After a month, I saw no “brighter smile” in the mirror. My breath improved about as much as any mint gum improves it. I didn’t expect a transformation and I didn’t get one, and I’d distrust anyone who tells you they did.
Is it legit or a scam?
It’s legit. Nathan & Sons is a real company with a real founder, hydroxyapatite is a real and safe ingredient, and the product is exactly what it says it is. So no, Underbrush is not a scam; you’re getting a well-made gum. Whether it’s worth what they charge is the better question, and a different conversation.
Two things do bug me, though, and a fair review has to name them:
- The “world’s first remineralizing chewing gum” line. It’s marketing: Underbrush’s own website compares itself to rival hydroxyapatite gums, so the claim carries more weight than it can hold.
- The counterfeit narrative. Go looking for negative reviews and you’ll quickly hit the brand’s explanation that the bad ones are counterfeits and that you should only ever buy direct. Amazon counterfeiting is real, and I don’t doubt some of that is true. But “ignore the criticism, it’s fake, buy only from us” is also a convenient way to wave off every complaint at once, and worth clocking as exactly that.
One more note, for anyone typing “underbrush gum reddit” in search of the unvarnished truth: I went looking too, and there’s surprisingly little genuine, independent discussion out there. Almost everything you’ll find on the product, the “SCAM or LEGIT?!” videos and the tidy review blogs, is affiliate content earning a cut of the sale. Keep that in mind when the internet feels suspiciously unanimous.
Is it worth the price?
The value depends entirely on why you’re buying. If you were going to chew gum anyway, you hate the idea of a plastic base, and the premium doesn’t scare you, then this is one of the nicer, cleaner gums you can buy, and I don’t regret the money. If you’re buying it as a dental treatment, to rebuild enamel or whiten, you’re paying supplement prices for a maybe, when a ten-dollar hydroxyapatite toothpaste has far more evidence behind it. Spend there first.
What it gets right, and where it overreaches
What Underbrush gets right: a plastic-free natural resin base (a real point of difference); a legitimate, safe active ingredient; sugar-free with tooth-friendly xylitol; a genuinely pleasant chew; and a founder who clearly sweated the formula.
Where it overreaches: “remineralize and whiten” leans on toothpaste evidence the gum format hasn’t earned; the hydroxyapatite dose is undisclosed; the flavor fades in about a minute; the pieces are small, with some quality-control wobble; it’s priced like a treatment it isn’t; and the marketing machine (the “world’s first,” the counterfeit narrative) works overtime.
Underbrush or a mastic gum?
For a lot of readers this is the real decision, because plenty of people find Underbrush while they’re actually looking for something else.
If what you want is a clean, plastic-free, sugar-free gum, and you like the idea of a little hydroxyapatite along for the ride, Underbrush is a real, non-scammy option. Buy it and enjoy it.
But if you came to functional gum for a hard chew, for jaw training, a real workout for the masseter, or the traditional mastic reasons people chew the raw resin, Underbrush isn’t it. It’s a soft, sweet, flavored gum that happens to contain a little mastic. What you’re describing is mastic gum: firm resin, one ingredient, no sweeteners, an actual jaw workout.
And I’m not going to claim Greco remineralizes your teeth better than Underbrush. It doesn’t, and it can’t, because it contains no hydroxyapatite at all. The two are built for different jobs. Underbrush is an oral-care gum; mastic gum is a chew. If the chew is what you’re after, I’ve written up how I think about buying mastic gum, and I put the two products head to head in a full Underbrush vs Greco comparison. Greco Gum shares our owner (Hubert Ventures LLC).
For the bigger picture of what’s actually going on in your mouth, start with the oral microbiome and build from there.
References
Evexia cites primary research and authoritative sources. Claims are traceable; where evidence is limited or mixed, we say so.
- Wierichs et al. — Efficacy of nano-hydroxyapatite on caries prevention: a systematic review & meta-analysis (Clinical Oral Investigations, 2022) · pmc.ncbi.nlm.nih.gov
- Amaechi et al. — Comparative efficacy of a hydroxyapatite and a fluoride toothpaste for remineralization (BDJ Open, 2019) · pmc.ncbi.nlm.nih.gov
- Naim & Sen — The remineralizing and desensitizing potential of hydroxyapatite: a narrative review of recent clinical evidence (J Funct Biomater, 2025) · pmc.ncbi.nlm.nih.gov
- Hassani et al. — Plant-mediated hydroxyapatite nanoparticles in a pistachio oleogum-resin gum: an in-situ study (J Mech Behav Biomed Mater, 2023) · sciencedirect.com
- Shen et al. — Remineralization of enamel subsurface lesions by sugar-free chewing gum containing CPP-ACP (J Dent Res, 2001) · journals.sagepub.com
- Hydroxyapatite (nano) confirmed safe for oral-care products — SCCS opinion summary (RIVM, 2025) · rivm.nl
- Underbrush (Mastic Mint) ingredient list — Healf product listing · healf.com
- Underbrush product claims and pricing — Nathan & Sons · nathanandsons.com
Frequently asked questions
Is Underbrush gum legit or a scam?
It's legit. Nathan & Sons is a real company, hydroxyapatite is a real and safe ingredient, and you get exactly the product described. The real question is whether it's worth the premium price.
Does Underbrush gum actually work?
As a sugar-free chew that freshens breath and boosts saliva, yes. As an enamel-rebuilding "remineralizing" treatment, the evidence for hydroxyapatite in gum form, as opposed to toothpaste, is essentially one small study, so keep expectations modest.
What are the ingredients in Underbrush gum?
Nano- and micro-hydroxyapatite on a natural tree-resin base (chicle, mastic, spruce, myrrh, acacia, candelilla), sweetened with xylitol and erythritol, plus zinc, magnesium, bentonite clay and flavor. It's sugar-free and plastic-free.
Is Underbrush gum good for your teeth?
It's unlikely to hurt them and may modestly help. It's sugar-free, and xylitol plus extra saliva is genuinely good for teeth. The hydroxyapatite might add a little, though that's unproven in gum form. Treat it as a supplement to brushing, not a substitute for it.
Is Underbrush gum worth the price?
If you'd chew premium gum anyway and want a clean, plastic-free option, it's a nice buy. As a dental treatment it's poor value, since a hydroxyapatite toothpaste costs less per use and has far better evidence behind it.
Is Underbrush the same as mastic gum?
No. It contains a little mastic in its resin base and sells a "Mastic Mint" flavor, but it's a soft, sweetened, flavored oral-care gum. Mastic gum is a firm, single-ingredient resin chewed for the jaw and gut, a different product for a different goal.
