A word on what this comparison can and cannot do. With no dose on either label and no trial on either gum, nobody can tell you which one remineralizes more. What can be compared is what each brand puts in the piece, what it tells you to do with it, what it claims, and what it charges. That is what follows.

At a glance

Halo vs Underbrush, side by side

Swipe sideways on mobile. Both brands' product pages as captured on 26 September 2026.

Part 1

The ingredient lists, word for word

Halo

Xylitol, Gum Base (Chicle), Nano-Hydroxyapatite, Natural Flavors, Flaxseed Oil, Rosehip Oil, Stevia, Menthol, Spearmint Oil, Peppermint Essential Oil.

Ten ingredients. Xylitol leads, which makes it the largest component; the base is chicle, a natural tree latex; nano-hydroxyapatite is third. The flaxseed and rosehip oils are what Halo calls its "BioFuse Oil Matrix", which the product page says "kills bad bacteria while leaving the good stuff untouched". Halo states it is formulated "without aspartame, artificial plastics, and rubbers".

Underbrush

Xylitol, Chicle gum base (chicle, candelilla wax, citric acid), Erythritol, Mastic gum, Spruce gum, Acacia gum, Mint flavor, Myrrh gum, Hydroxyapatite (nano and micro), Calcium carbonate, Calcium bentonite clay, Magnesium carbonate, Zinc gluconate, Terpene blend (Menthone, Carvone, Cineol).

That is the Mastic Mint list, about 16 components counting the base's sub-ingredients. Xylitol leads here too, followed by the chicle base, erythritol, and three tree resins that give Underbrush its firm, sap-like chew. Hydroxyapatite comes ninth, described as nano and micro, after the flavour and myrrh. Then come several minerals and salts: calcium carbonate, bentonite clay, magnesium carbonate and zinc gluconate. The Tropic Twist flavour uses a different list with sorbitol, dicalcium phosphate, stevia, monk fruit and fruit powder.

What the lists tell you

Both brands put xylitol first, which is where a dentist would want it. Both use natural bases rather than synthetic polymers. The difference is philosophy: Halo is a short recipe built around three named actives; Underbrush is a longer recipe that adds several minerals and resins, with hydroxyapatite in the middle of the list. On US labels, ingredients above 1% run in descending order, so Halo's nano-hydroxyapatite sits higher relative to the rest of its recipe than Underbrush's does. Without a milligram figure from either brand, that is as far as the labels can take you. Our comparison of hydroxyapatite per piece found that, as of 22 August 2026, neither brand published one.

Part 2

Chewing time: 5 minutes vs 30

This is the most practical difference between the two, and it is easy to miss. Halo's directions read: "Chew 1-3 pieces per day, after meals or acidic beverages. Chew for at least 5 minutes to get dental benefits." Underbrush's read: "Chew 1-2 pieces after meals for at least 30 minutes or as long as you'd like," while its FAQ suggests "15 to 20 minutes after meals" as "roughly the window in which most chewing gum delivers its saliva-stimulating benefit".

The evidence sits closer to Underbrush's number. The EU-authorised health claim for sugar-free gum, that it helps neutralise plaque acids and maintain tooth mineralisation, is tied to chewing for at least 20 minutes after eating or drinking. Five minutes does raise saliva, but it cuts the chewing window well short of what that claim is based on. Our guide to how long to chew gum explains where the 20 minutes comes from. Whichever gum you choose, chewing it for 20 minutes after a meal is the part you control.

There is a flavour trade-off here. A firm resin chew like Underbrush is built to be chewed for a long time; a softer chicle gum may lose flavour sooner, which is one reason short chewing times appear on some labels. The saliva effect does not depend on flavour, so keep chewing.

Part 3

The claims, side by side

Halo

Halo's product page says that over time the BioFuse Oil Matrix, nano-hydroxyapatite and xylitol "will reduce harmful microbiome, remineralize damaged enamel, and keep cavities at bay". When we reviewed Halo on 22 August 2026, its benefit tiles ran to "Bone Density Support" and "Whole-Body Benefits", and its BioFuse science page showed a "48%" reduction in harmful bacteria "in just 2 weeks", footnoted to "S. mutans saliva levels from human clinical trial", and a "99%" figure footnoted to "in vitro saliva tests". No institution, sample size, date, publication or link was given for either figure, so neither can be checked from outside the company. Details are in our full Halo review.

Underbrush

Underbrush's page on 26 September 2026 listed "Natural & Gentle Whitening" among its benefit tiles and "Natural Teeth Whitening" among what customers "report in just 3 weeks", alongside plaque removal, fresher breath and less sensitivity. It states it contains "ZERO Plastics, PFAS, parabens" and is "Made in USA with globally sourced ingredients". Its product page carries roughly 39 numbered citations; when we spot-checked eight of them against PubMed and CrossRef on 27 August 2026, three resolved cleanly and five did not, as documented in our citation audit.

Neither brand's claims are backed by a published trial on its own gum. The one peer-reviewed trial of a hydroxyapatite gum we found tested a calcium hydroxyapatite gum on dentine sensitivity (Porciani 2014, PMID 25122980); a 2023 in situ study tested nano-hydroxyapatite in a pistachio-resin gum on enamel minerals (Hassani 2023, PMID 37852085). Neither is Halo or Underbrush, and neither measured cavities. On whitening specifically, a gum without peroxide can at most help with surface stains; neither gum bleaches teeth.

Part 4

The extras in each recipe, explained

Beyond hydroxyapatite and xylitol, each gum adds ingredients that shape its character. None of them has a published trial in these gums, so here is what each is, plainly, without claims.

• Erythritol (Underbrush). A second sugar alcohol, alongside xylitol. Like xylitol, oral bacteria cannot ferment it into acid; it adds sweetness and bulk.
• Mastic, spruce, acacia and myrrh gums (Underbrush). Natural resins and gums that make the chew firm and long-lasting, and give it a resin taste that Reddit users mention often.
• Calcium carbonate (Underbrush). A mild polishing mineral used in many toothpastes; in a gum it may add a little polishing action on surface stains.
• Calcium bentonite clay and magnesium carbonate (Underbrush). Mineral powders; bentonite is used in some natural oral-care products for texture and binding.
• Zinc gluconate (Underbrush). A zinc salt; zinc compounds are used in many toothpastes and mouthwashes against plaque and odour.
• Flaxseed and rosehip oils (Halo). Plant oils that Halo calls its BioFuse Oil Matrix and credits with targeting harmful bacteria. We found no published study of these oils in a chewing gum; the only figures Halo shows come from an unnamed trial.
• Stevia (Halo, and Underbrush's Tropic Twist). A non-sugar sweetener.

Put simply, Underbrush layers several minerals and resins around a smaller share of hydroxyapatite; Halo keeps the recipe minimal and relies on its oil blend as the differentiator. Neither approach has been tested head to head.

Part 5

What people ask on Reddit

The question "Halo or Underbrush?" does come up. In July 2026 a user in r/NoStupidQuestions asked "Is Remineralizing gum like Halo or Underbrush worth it?", explaining they were trying to solve a whitening problem and that most reviews they had found had "only taken the flavor into account". The replies did not pick a brand. One separated the two jobs cleanly: "Remineralizing gum can help to prevent cavities and decay, but won't repair already damaged teeth. Whitening gum can remove surface stains from coffee/smoking/etc but won't remove yellowing from age/decay." Another pointed out that the poster was asking a remineralizing product to whiten, "which isn't the point of remineralization", and suggested asking a dentist. That is sound advice for both brands.

On Underbrush specifically, our round-up of eleven Underbrush threads found consistent themes: a genuine product, small firm pieces that people chew two or three at a time, flavour that fades in under a minute with a resin aftertaste, and "scam" worries that turn out to be about counterfeit boxes from copycat sellers rather than the brand. Nobody in those threads asked how many milligrams of hydroxyapatite a piece contains. We found far less Reddit discussion of Halo, which is newer to the category.

Part 6

The shared science, in brief

Because both gums rest on the same two actives, the evidence question is the same for both, and it has three layers.

Chewing sugar-free gum. This is the best-established part. Chewing after meals raises saliva flow; saliva buffers the acid that follows eating and carries calcium and phosphate back to enamel. The EU authorises a health claim for sugar-free gum on this basis, tied to at least 20 minutes of chewing after eating or drinking. Any sugar-free gum does this, including both of these.

Hydroxyapatite. Strong in toothpaste, thin in gum. A systematic review and meta-analysis of nano-hydroxyapatite for caries prevention (Wierichs 2022, PMID 35103837) supports the ingredient in toothpaste. In gum, we found only two studies, on sensitivity (PMID 25122980) and on enamel minerals in situ (PMID 37852085), neither measuring cavities and neither testing these brands. Without a dose on either label, you also cannot tell how either gum's amount compares with what was studied.

Xylitol. Real but modest. Older trials found fewer cavities with several grams a day; the Cochrane review rated the evidence for xylitol gums and similar products as insufficient to determine a benefit (Riley 2015, PMID 25809586). Both gums lead with xylitol, but neither states grams per piece, so you cannot tell whether two pieces a day come near the studied range. Our xylitol gum ranking lists brands that do state it.

The practical conclusion is identical for Halo and Underbrush: the chewing is the part with the strongest backing, so chew long enough after meals; the hydroxyapatite and xylitol are plausible extras whose amount you cannot check.

How to try either one sensibly

• Start with the smallest pack without a subscription, if the store allows, to test the chew and flavour.
• Chew after your main meal for 20 minutes, whatever the label says.
• Keep brushing twice a day with a fluoride or hydroxyapatite toothpaste; neither gum replaces it.
• Judge on what you can notice (fresher mouth, less snacking, comfort), and leave cavity questions to your next check-up.

Part 7

Who is behind each gum

Halo is made by Something Nice, an oral-care company whose own pages date it to 2020 and list Dr. Ben Winters, DDS/MS, an orthodontist known online as The Bentist, as Founder and Chief Innovation Officer. A named, credentialed clinician on the label is rare in this category, and it is the strongest point in Halo's favour: his professional reputation is attached to the product. Something Nice also sells toothpastes, whitening strips and floss; its site shows a "300,000+ smiles" figure, which is its own count.

Underbrush is made by Nathan & Sons LLC, which holds the US trademark on the Underbrush name. Trade press has reported the brand passing $30 million in sales in 2024, and its product page showed "70K+ bought in past month" on 26 September 2026. It is the best-known remineralizing gum in the US, and the most discussed on Reddit; our round-up of Underbrush on Reddit and our profile of Nathan & Sons cover the company and the conversation.

Part 8

Price per week and per piece

Both brands price two packs at $29.99, and both describe one pack as roughly one week at two pieces a day, with four packs as about a 30-day supply. That makes them almost identical at the entry level: about $15 a week.

Both brands' stores, 26 September 2026. Halo displayed per-piece prices of $0.57 to $0.67 on its subscription offers; subscription discounts on both sites change frequently.

At larger sizes Underbrush is clearly cheaper: $44.99 for four packs against Halo's $56.98. Halo displayed per-piece prices between $0.57 and $0.67 on its subscription options; Underbrush does not state a per-piece price on the page we read. For comparison, Minvelle is €24.99 for 18 pieces, about €1.39 a piece at one piece a day.

Buying safely

Popular gums attract copies. Reddit threads about Underbrush describe counterfeit boxes sold through copycat websites and some marketplace sellers, as our Underbrush round-up documents. The official stores are nathanandsons.com for Underbrush and somethingnicecompany.com for Halo. If a deal looks unusually cheap or the site is not the brand's own, check the domain and the seller before you pay, and compare the ingredient list on the box with the one on the official product page.

Returns and shipping

Underbrush advertises a "30-Day Satisfaction Guarantee" and free shipping on orders over $50. Halo's page emphasises subscribe-and-save offers; when we reviewed it in August, the one-time purchase was out of stock and the subscription and a marketplace listing were the live ways to buy. Check each store's current policy before ordering, especially if you want to try a single order without a subscription.

Part 9

Which one should you buy?

Choose Underbrush if

• you want a firm, long-lasting chew you can keep going for 20 to 30 minutes;
• you like flavour choice: mint, berry, cinnamon-mastic, tropical;
• price at the larger sizes matters: four packs are $12 cheaper than Halo's;
• you want extra minerals and zinc in the recipe, accepting that hydroxyapatite sits further down the list.

Choose Halo if

• a named, credentialed clinician behind the product matters to you;
• you prefer a short ingredient list with nano-hydroxyapatite near the top;
• you want a softer chicle chew, and you are willing to chew it for 20 minutes despite the 5-minute direction.

Either way

• Neither states its dose, so neither can be compared with the research on hydroxyapatite amounts.
• Neither replaces brushing with a fluoride or hydroxyapatite toothpaste, and neither reverses cavities.
• Chew after meals, for at least 20 minutes, and keep your check-ups.

Part 10

Where Minvelle fits, honestly

We make a third option, so here is the plain comparison. Minvelle publishes what neither Halo nor Underbrush does: 5.7 mg of nano-hydroxyapatite per 1.9 g piece, printed on the box, with 817 mg of xylitol, the full ingredient list, the particle size and a batch certificate. It is one piece a day, chewed for at least 20 minutes after a meal. It costs more per piece than Underbrush at its larger sizes, it comes in one flavour today, and like both of them it has no clinical trial on the finished gum. Underbrush beats us on flavour choice and per-week price; Halo beats us on having a clinician's name on the label. We win on disclosure.

What a gum cannot do

• It does not replace brushing. A gum does not remove plaque the way a toothbrush and paste do.
• It does not replace fluoride toothpaste. If your dentist has recommended fluoride, keep using it.
• It does not repair a cavity. No gum and no toothpaste fills a hole in a tooth. That is a job for a dentist.
• It does not bleach teeth. There is no peroxide in it; at most it helps with surface stains between brushings.
• It has not been in a clinical trial. There is no clinical trial on the finished Minvelle gum. What we publish is the dose, the full ingredient list and a batch certificate from lab testing of the finished gum.

Minvelle prints the dose on the box: 5.7 mg nano-hydroxyapatite per piece. See the gum.

In fairness

What each gum does well

Halo has a named, credentialed orthodontist accountable for it, puts xylitol first, uses a natural chicle base, keeps the recipe short, and makes no whitening claim on the gum page we reviewed. Underbrush built the category's audience, offers the widest flavour range, uses a genuinely distinctive resin chew, puts xylitol first, tells people to chew long enough, and is cheaper at the larger sizes. Both are real products from real companies with published ingredient lists. The shared gap, no dose and no trial, is the category's gap, and we hope both close it.

How we checked

Method and conflict of interest

We read both brands' live product pages and store catalogs on 26 September 2026 and drew on our earlier dated reviews: Halo (captured 22 August, reviewed 5 September 2026) and Underbrush (reviewed 1 September 2026, citation spot-check 27 August 2026). We resolved every PMID in PubMed on 26 September 2026. We did not buy or lab-test either gum for this comparison. Minvelle sells a competing gum; that is a direct conflict of interest, which is why we name where each brand beats us.

The verdict

Halo vs Underbrush, in one paragraph

Same price at the entry level, same core idea, different execution. Underbrush gives you more flavour choice, a firmer resin chew, more added minerals and a lower price at larger sizes, with hydroxyapatite further down its list and whitening language on its page. Halo gives you a clinician's name, a short recipe with nano-hydroxyapatite third, and bacteria figures it has not published a source for. Neither states its dose or has a trial on its gum. Choose on chew, flavour and price, and whichever you choose, chew it for 20 minutes after a meal.

Both brands also appear in our ranking of the best remineralizing gums for 2026, where 14 brands are sorted by what they publish per piece.

Questions, answered

The things people actually ask