Glycerin

What it is

Glycerin (glycerol, propane-1,2,3-triol) is a trihydric alcohol with the formula C₃H₈O₃ — a colourless, viscous liquid with a mildly sweet taste. Industrially it is obtained as a by-product of fat hydrolysis in soap or biodiesel manufacture, and also synthetically from propylene.

Glycerin has been used in toothpastes and mouthwashes since the late 19th century: the first commercial pastes of the 1890s (Colgate) already contained glycerin as a base. Today it is present in virtually all commercial pastes and rinses at concentrations from 5 to 30%, simultaneously fulfilling several technological and functional roles.

How it works

The primary function is hygroscopicity and moisture retention. Glycerin contains three hydroxyl groups (-OH) that actively form hydrogen bonds with water molecules. In a paste formulation it prevents the tube from drying out after opening (anti-crystallisation effect) and maintains optimal moisture content during storage. On contact with mucosa, glycerin creates a temporary moisturising layer, reducing the sensation of dryness.

The second function is as a plasticiser and texture regulator. In combination with thickeners (carbopol, CMC), glycerin influences paste rheology: it provides smoothness on extrusion from the tube, prevents emulsion separation and gives a pleasant creamy feel on application. A concentration of 10–20% is optimal for a classic creamy texture.

The third function is as a solvent and co-solvent. Glycerin facilitates the solubility of a number of ingredients with limited water-solubility (menthol, certain antibacterials, plant extracts), ensuring their even distribution through the formulation.

Efficacy

Glycerin has no independent therapeutic action on dental hard tissues. Its value is technological: pastes without glycerin (or its analogue sorbitol) are unstable, separate on storage and deliver unsatisfactory texture. This is why its concentration in a formulation is a trade-off between technological necessity and cost of goods.

An important clarification on a popular myth: glycerin at concentrations typical for toothpastes (10–25%) does not block enamel remineralisation. Studies have shown that rinsing the paste with water after brushing effectively removes glycerin from the enamel surface. Claims that glycerin "coats teeth with a protective film and interferes with remineralisation" have no scientific support.

Safety

Glycerin holds GRAS (Generally Recognized As Safe) status in the USA, is approved by FDA and EFSA, and is listed in the INCI register. Completely safe when ingested in quantities typical of toothpaste use. It does not irritate the oral mucosa even with prolonged use.

Vegetable (palm-free) glycerin, derived from rapeseed or sunflower oil, is available as an option for "green" formulas — the composition is identical to petrochemical glycerin, but it satisfies organic and natural-certification requirements.

Role in the QDRO formula

Glycerin is present in every QDRO formula as the base humectant at 10–18%. In the v.daily line it forms the foundation of the soft, creamy texture characteristic of an "everyday comfort" product. In the v.pro line its concentration is minimised (10–12%) to leave room for the active remineralising ingredients while maintaining the necessary textural profile.

In QDRO mouthwashes, glycerin is used at a lower concentration (3–8%) to deliver a pleasant aftertaste and a soft mucosal feel without stickiness.