Fig. 4

Cryo-TEM images of the mineralizing film and its SAED pattern at 0 h (a, f), 6 h (b, g), 8 h (c, h), 12 h (d, i) and 24 h (e, j) in artificial saliva. a, b The spherical ACP nanoparticles in the mineralizing film are approximately 30–80 nm in diameter and stable in artificial saliva over 6 h. c The ACP nanoparticles decreased in size and fused at 8 h. d, e Most of the ACP nanoparticles transformed into HAp at 12 and 24 h. f–j SAED patterns of the mineralizing film