A Tooth Is Not a Single, Uniform Structure

Beneath what looks like a smooth, hard surface lies a layered mineral structure: each layer differs from the next in density, crystal size, and composition. What all the layers share is one basic building block — a crystal lattice in which calcium holds a fixed place.

Andraditys gathers the scientific background on this structure: from the crystal lattice itself, through the cells that lay it down during tooth development, to the saliva that continually bathes the surface. At the end stands the wording of the EU claim on calcium, quoted unchanged.

The European Food Safety Authority (EFSA) assessed the scientific basis for this, and the European Commission authorized a health claim on that basis.

From Crystal Lattice to Finished Structure

The mineral portion of tooth substance consists largely of a compound called hydroxyapatite, with the chemical formula Ca₁₀(PO₄)₆(OH)₂. That formula looks technical at first glance, but it describes a simple numerical ratio: for every ten calcium ions there are six phosphate groups and two hydroxide ions — a fixed proportion that repeats in every unit cell of the crystal.

Two Different Sites for the Same Ion

Within this lattice, the ten calcium ions do not all sit at the same kind of position. Crystallographic work distinguishes two groups: four ions form columns along one axis of the crystal, while the remaining six sit in triangular arrangements around a central channel through which the hydroxide ions run. Both groups contribute to the stability of the lattice, though with different binding geometry to the surrounding oxygen atoms of the phosphate groups.

Calcium is needed for the maintenance of normal teeth. EU-authorized wording · Regulation (EU) No 432/2012.

The Maturation Stage: How Calcium Reaches the Developing Enamel

Before a tooth erupts, the enamel passes through a sequence of developmental stages. In an early phase, cells called ameloblasts lay down a white, still mineral-poor matrix. Only in the later maturation stage does the shape of these cells change: the surface facing the matrix folds and grows substantially larger as a result, which is why the scientific literature refers to the tissue at this stage as having “ruffled ameloblasts.”

Across this enlarged surface, the maturation stage moves many times the amount of calcium into the tissue that was needed during the earlier laying-down of the matrix. Membrane-bound transport proteins carry the ions through the cell in a directed manner, while organic remnants of the original matrix are broken down and removed from the tissue at the same time. The result of this stage is a tissue whose mineral content rises many times over compared with the early matrix.

Saliva as an Ion Reservoir at the Crystal Surface

The outermost boundary of the tooth does not exist on its own — it sits in direct contact with saliva. Saliva holds calcium and phosphate ions at a concentration higher than a simple aqueous solution could ordinarily sustain, a state chemistry calls supersaturation. This state is made possible in part by small, calcium-binding salivary proteins such as statherin, which delay the ions from precipitating out of solution prematurely.

At the crystal surface itself, this creates a continuous exchange: individual ions detach from the lattice while others attach anew from the surrounding fluid. Which direction prevails depends on the local pH and on the ion concentration at any given moment — a purely chemical equilibrium that the regulation itself does not describe, and that this text presents solely as scientific background.