High-resolution transmission electron microscopy of adult human peritubular dentine.

Single crystals from adult human peritubular dentine were studied by high-resolution transmission electron microscopy. Periodic fringe patterns were obtained from which the exact shape of the inorganic crystals were deduced. The crystals were found to have a mean length of 36.00 +/- 1.87 nm, a mean width of 25.57 +/- 1.37 nm, and a mean thickness of 9.76 +/- 0.69 nm. They consisted of platelets with a mean width-to-thickness ratio of 2.61, each being a flattened hexagonal prism of hydroxyapatite. Such conclusions are based upon the electron diffraction patterns that we obtained, and our comparison of the values of the periodic, equidistant fringes seen along different planes of sectioning with the corresponding theoretical values for hydroxyapatite.