Fig. 3. APT 3D reconstructed volumes of human dental enamel HAP nanowires containing a Mg-rich precipitate and organic matter.

(A) ²⁴Mg²⁺ (overlapping with ¹²C⁺) atom distribution. (B) Na isosurface (0.5 at %) showing Mg-ACP intergranular phase. (C) Isosurface ¹²C²⁺ (0.18 at %) (precipitate A), 1 at % ²⁴Mg²⁺ isosurface (precipitate B), and 0.7 at % ²⁴Mg²⁺ (Mg-ACP intergranular phase). (D) Proxigrams of precipitate A, precipitate B, and Mg-ACP (based on the sum of ACP interfaces).