Baking Soda for Teeth: What the Science Actually Says

Baking soda has an RDA of about 7. Most standard toothpastes sit between 70 and 150. By that measure, baking soda is one of the mildest abrasives available. The problem isn't that it's too harsh — the problem is what people mix it with when they try to turn it into a whitening treatment.

What RDA measures — and why baking soda scores so low

RDA stands for Relative Dentin Abrasivity. It's not how gritty something feels in your mouth. It's a standardised measure of how much the material wears dentin under controlled conditions.

Sodium bicarbonate (NaHCO₃) has a hardness roughly equivalent to dentin itself — softer than enamel, far softer than the abrasives in most commercial toothpastes. That's why its RDA hovers around 7 in pure form, rising to 35–53 when formulated at 50–65% concentration in a dentifrice.

This is why baking soda is used in formulations for patients with erosive risk or dentinal sensitivity. The mechanical load on tooth structure is minimal.

Low abrasivity doesn't mean low efficacy

Baking soda cleans well — but not because it scrubs hard. Several mechanisms work together.

When it dissolves in saliva, bicarbonate ions give the tooth surface a negative charge. Bacteria in plaque also carry a negative charge. Like charges repel — the biofilm detaches more easily from the surface.

At the same time, baking soda raises pH. After eating, plaque pH can drop to 4–5. Sodium bicarbonate buffers that acid and brings pH back to a safe range. Cariogenic bacteria — primarily Streptococcus mutans — are less effective in alkaline conditions.

A third factor: alkaline pH amplifies the detergent activity of surfactants already present in the paste.

The mechanism is physical chemistry and electrochemistry, not mechanical scraping.

Surface stains: yes. Intrinsic colour: no

This is where "whitening" claims get distorted.

Teeth aren't yellow because they're dirty. Their natural colour comes from dentine — the tissue beneath translucent enamel. Dentine is yellowish by structure. Enamel lets that colour through.

Baking soda acts on what's on the outside: plaque, pellicle, pigment deposits from coffee and tea. These are extrinsic stains. Regular brushing removes them. The teeth look cleaner and brighter. This is extrinsic stain removal — not whitening.

Changing intrinsic tooth colour requires hydrogen peroxide. It penetrates the enamel, breaks down chromogens inside the organic matrix of dentine. Baking soda physically cannot do this — it does not penetrate tooth structure.

Baking soda removes what settled on the outside. That's honest. But that's cleaning, not whitening.

Li Y.'s 2017 review in JADA (PMID 29056186) confirms: bicarbonate-containing dentifrices effectively remove extrinsic stain and produce a visible brightening effect. The effect is real. The mechanism is entirely different from what happens in professional whitening.

The real risk: not the soda itself, but what gets added to it

Plain baking soda in water is a safe, low-abrasion abrasive. The internet routinely suggests improvements.

Lemon juice and baking soda. Lemon juice has a pH of around 2. At that level, enamel demineralises. The neutralisation reaction buffers some of the acid, but enough acidity remains to soften the enamel surface. Any mechanical contact after that — even light rubbing — removes weakened structure.

Hydrogen peroxide and baking soda. Commercial pastes containing H₂O₂ are formulated and tested at stable concentrations. A DIY mixture is neither.

What plain baking soda doesn't provide

Even if baking soda cleans effectively, it leaves one essential gap: caries protection.

Fluoride in toothpaste integrates into the enamel crystal lattice, forming fluorapatite — more acid-resistant than the native hydroxyapatite. The 2019 Cochrane review by Walsh et al. (PMID 30829399) confirms: regular use of fluoride toothpaste is the primary non-professional intervention for caries prevention, with a dose-dependent relationship between fluoride concentration and protective effect.

Pure baking soda dissolved in water contains no fluoride. Using it daily instead of regular toothpaste means opting out of fluoride protection every single day. For patients with elevated caries risk, this matters.

Commercially formulated baking soda toothpastes address this: they combine sodium bicarbonate with fluoride at standardised concentrations.

What this means in practice

Sodium bicarbonate earns its place as a dentifrice ingredient: mild abrasive, well studied, biocompatible, with real evidence for plaque removal and extrinsic stain reduction.

As a standalone replacement for toothpaste, it removes fluoride protection from the equation. As a home whitening agent mixed with lemon or peroxide, it creates conditions for irreversible enamel loss.

If you want the benefits of baking soda, choose a commercial paste that includes both sodium bicarbonate and fluoride. If you want professional-grade remineralisation alongside gentle cleaning, look at formulations where bicarbonate works alongside active mineral compounds — not a kitchen improvisation.

Expecting baking soda to "whiten" in a clinical sense means conflating stain removal with changing tooth colour. These are different goals with different tools.

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Sources: Valkenburg et al., 2019 (PMID 30734996) · Li Y., 2017 (PMID 29056186) · Putt & Milleman, 2008 (JADA Suppl, RDA data) · Walsh et al., Cochrane 2019 (PMID 30829399) · Africa Check / ADA: acid and enamel erosion · ISO 11609