Toothpaste packaging rarely mentions abrasivity, yet the property matters for anyone with exposed root surfaces. The measure behind it is more specific than most descriptions suggest.
Abrasives are what the paste is mostly made of
Toothpaste removes surface stain and film partly through mild abrasion, using particles of materials such as hydrated silica, calcium carbonate or alumina.
Without an abrasive component, a paste would rely entirely on detergents and would remove far less of the acquired film that pigments bind to.
The engineering problem is therefore balancing enough abrasion to clean against little enough to avoid wearing tooth structure. Different products resolve that balance in different places depending on what they are marketed to do.
The test measures dentine, not enamel
Standard abrasivity testing brushes irradiated dentine specimens under controlled load and stroke count, then measures material removed against a reference abrasive.
Dentine is used because it is far softer than enamel and produces measurable wear within a practical test, whereas enamel would barely register.
The resulting number is a ratio against the reference rather than a physical quantity, which is why it has no units attached.
Laboratory conditions are not brushing conditions
The test applies consistent force, a fixed brush and a specified slurry dilution, none of which match the variability of real use.
Brushing force, brush stiffness, technique and how much the paste is diluted by saliva all change the actual wear a person produces.
A score is therefore useful for ranking products against one another and unreliable as a prediction of what any individual mouth will experience.
Acid changes the picture entirely
Enamel softened by dietary acid is temporarily far more susceptible to abrasion, and brushing during that window removes more than the same brushing would otherwise.
Erosion and abrasion acting together produce more loss than either alone, which is why advice on acidic drinks and advice on brushing are linked.
Exposed root surfaces are the most vulnerable of all, since cementum and dentine wear at a fraction of the force enamel withstands.
Who has reason to consider it
People with recession, existing wear notches, sensitivity or a history of erosion have the most to gain from a lower abrasivity product.
Whitening pastes commonly sit at the higher end, since surface stain removal is largely what they do, and that trade-off is worth knowing about.
Which paste suits a particular mouth depends on findings a dentist or hygienist can see, and existing wear should be assessed rather than self-managed.