Glycerine — sometimes called glycerol — is one of the most misunderstood ingredients in oral care.
Once dismissed in online forums as a “barrier to remineralisation,” it’s become the focus of widespread misinformation, often traced back to the writings of chemist Gerard F. Judd. But as with many persistent internet myths, those claims are not supported by experimental evidence.

At Truthpaste, we use glycerine in our formulations for its proven functional and oral-care benefits. Here, we take a closer look at what peer-reviewed science really says about this ingredient, how it interacts with the oral environment, and whether it truly affects enamel remineralisation.

What Glycerine Is and Why It’s Used

Chemically, glycerine (C₃H₈O₃) is a trihydric alcohol — a clear, viscous liquid with three hydroxyl (–OH) groups that attract water. This hygroscopic nature makes it an effective humectant, helping toothpaste stay moist and preventing it from drying out in the tube or jar.

Beyond its physical role, glycerine contributes to:

• Moisture retention: maintaining hydration in the mouth.

• Texture and spreadability: helping the paste distribute evenly across teeth and gums.

• Stability: supporting a consistent formulation that suspends active ingredients effectively.

In short, glycerine helps a toothpaste work — ensuring that actives such as hydroxyapatite, xylitol, or botanical extracts remain evenly dispersed and functional during use.

The Origin of the Myth

The notion that glycerine “coats the teeth” and prevents remineralisation is not grounded in scientific research. It appears to originate from the late chemist Dr. Gerard F. Judd, whose writings circulated widely online in the early 2000s. Judd claimed that glycerine left a film over enamel that required “27 rinses” to remove and thus blocked minerals from binding to the tooth surface.

However, these claims were never supported by published data, peer-reviewed research, or experimental verification. No controlled studies have demonstrated that glycerine inhibits calcium or phosphate uptake, or that it forms an impermeable barrier on enamel.

In fact, glycerine is highly soluble in water and saliva, meaning it won't leave a residue on teeth.

What the Science Actually Shows

1. No Evidence of Remineralisation Inhibition

There are no peer-reviewed studies demonstrating that glycerine interferes with enamel remineralisation or ion exchange.

In fact, the opposite may be true: glycerine is water-soluble, readily rinsed, and does not form a polymeric or hydrophobic film on enamel. Unlike certain surfactants or silicones, it does not adhere strongly to hydroxyapatite surfaces. When combined with brushing and saliva flow, residual glycerine is quickly diluted and removed.

2. Compatibility with Active Ingredients

Formulation studies have shown that glycerine can act as a vehicle without reducing the bioavailability of other active ingredients. For example, when used in chitosan-chlorhexidine membranes, glycerine modified mechanical properties but did not alter antimicrobial activity against Streptococcus mutans — one of the main bacteria responsible for tooth decay (Frontiers in Microbiology, 2024).

This suggests that glycerine does not chemically interfere with other oral-care actives — it simply supports texture and stability.

3. Supports Moisture and Tissue Health

In clinical and in-vitro models, glycerine has been shown to retain moisture and soothe oral mucosa:

• A randomized controlled trial on patients with dry mouth found that glycerine provided immediate relief from xerostomia symptoms, although the effect diminished after two hours (European Journal of Oral Sciences, 2020).

• An in-vitro reconstructed oral mucosa study found that while very high concentrations of glycerine (42–85%) affected cell proliferation, lower levels typical in cosmetic and oral formulations showed no disruption of tissue integrity (Journal of Applied Oral Science, 2019).

These findings reinforce that glycerine’s humectant properties can be beneficial in maintaining oral comfort — especially for people with dry mouth or irritation.

4. Potential Microbiome Benefits

Recent research shows that Streptococcus sanguinis — a bacterium commonly found in healthy, non-cariogenic oral microbiomes — can metabolise small amounts of glycerol in ways that help it maintain a competitive advantage over cavity-causing bacteria such as S. mutans.

In other words, in small physiological amounts, glycerine may actually help maintain microbial balance rather than disrupt it.

Understanding the Limits

While glycerine contributes useful properties to toothpaste, it’s not a magic ingredient — nor is it a hazard.
It does not remineralise teeth by itself, but neither does it prevent remineralisation when other actives (such as hydroxyapatite, fluoride, or calcium phosphates) are present.

At the concentrations used in toothpaste (typically under 20%), glycerine:

• is non-toxic,

• rinses away easily,

• and does not form a barrier to mineral exchange.

Why Truthpaste Uses Glycerine

Truthpaste formulations are designed around function, safety, and evidence.
We use plant-derived glycerine for its moisture-retaining, texture-enhancing, and microbiome-friendly qualities. It helps distribute active ingredients such as hydroxyapatite and botanical extracts evenly across enamel and gums, improving the delivery of minerals where they’re needed most.

Crucially, our formulations are tested for pH balance, ionic compatibility, and stability, ensuring that remineralisation agents remain fully active and that glycerine plays a supportive—not obstructive—role.

The Takeaway

Misinformation spreads easily, especially when scientific language is taken out of context. Glycerine has been unfairly vilified by outdated, anecdotal claims, but the evidence paints a very different picture.

According to current research, glycerine:
✅ Does not block remineralisation.
✅ Helps maintain moisture and oral comfort.
✅ May support beneficial oral bacteria.
✅ Enhances product texture and stability.

At Truthpaste, every ingredient is chosen for a reason — and glycerine earns its place for both practical and scientific ones.

References

1. Andersen, J. et al. (2019). Influence of glycerol concentration on reconstructed human oral mucosa model. Journal of Applied Oral Science, 27(4):e20180412.

2. Petrou, M. et al. (2020). Clinical evaluation of saliva substitutes in xerostomia management. European Journal of Oral Sciences, 128(3):201–210.

3. Chan, A. et al. (2024). Functional properties of chitosan–glycerol–chlorhexidine membranes against oral biofilms. Frontiers in Microbiology, 15:1430954.

4. Ganesan, S. et al. (2023). Glycerol metabolism and hydrogen peroxide production by oral Streptococcus sanguinis. Microbiology Spectrum, 11(4):e00689-23