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Cleaning abrasives

Hydrated silica

Also listed as silica, silicon dioxide, precipitated silica

The standard toothpaste abrasive and thickener. It scrubs off plaque and surface stain; how harsh a paste is depends on the grade, which labels rarely show.

Moderate evidenceTypical strength: Roughly 10-25% of a toothpaste (combined cleaning and thickening grades)

What it is

Hydrated silica is a synthetic, non-crystalline form of silica ground to fine particles. Grades differ: some mainly thicken the paste, others are cleaning abrasives. It is compatible with every type of fluoride, which is why it is the most common abrasive.

Abrasiveness is measured as RDA (relative dentin abrasivity). International standards cap toothpaste at 250; most everyday pastes sit well below that, while 'whitening' pastes are often higher. It is not the crystalline silica dust linked to lung disease, and there is no inhalation risk in a paste.

How strong is the evidence?

Moderate evidence

Abrasives are what let toothpaste remove extrinsic stain and help brushing clear plaque, shown in lab and short clinical stain studies. Much of the literature comes from manufacturers. Whether a particular paste's abrasivity wears exposed root surfaces over years is not well studied in people.

What it's used for, checked

Removes surface stains

Holds up

Its cleaning action is how most 'whitening' toothpastes work: they remove stain; they don't change tooth colour.

Whitens teeth beyond their natural shade

False

Only peroxide bleaching changes intrinsic colour.

Damages enamel

Mixed

Within the 250 RDA limit, wear on healthy enamel is small; exposed dentine and hard brushing are the real risk.

Works well with

  • sodium-fluoride
  • stannous-fluoride

Who should be careful

  • If you have receding gums, exposed roots, erosion or sensitivity, choose a low-abrasion paste and a soft brush; ask your dentist, as RDA is rarely printed on the tube.
  • Brushing hard does more damage than the abrasive grade.

The studies

Every citation is checked against its PubMed record.

  1. Whitening toothpastes: a review of the literature.
    Joiner A · J Dent · 2010 · Narrative review (industry author)

    The abrasive system is the key functional ingredient of whitening toothpastes, designed to remove extrinsic stain without undue wear; peroxides, enzymes, pyrophosphates or optical agents may be added. Clinical tests typically run 2-6 weeks and measure surface stain.