Intrafibrillar Mineral May be Absent in Dentinogenesis Imperfecta Type II (DI-II)

摘要

High-resolution synchrotron radiation computed tomography (SRCT) and small angelx-ray scattering (SAXS) were performed on normal and dentinogenesis imperfecta type II (DI-II) teeth. Three normal and three DI-II human third molars were used in this study. The normal molars were unerupted and had intact enemal; donors were female and ranged in age from 18-21y. The DI-II specimens, which were also unerputed with intact enemal, came from a single female donor age 20y. SRCT showed that the mineral concentration was 33% lower on average in the DI-II dentin with respect to normal dentin. The SAXS spectra from normal dentin exhibited low-angel diffraction peaks at hamonics of 67.6 nm, consistent with nucleation and growth of the apatite phase within gaps in the collagen fibrils (intrafibrillar mineralization). In contrast, the low-angel peaks were almost nonexistent in the DI-II dentin. Crystallite thickness was independent of location in both DI-II and normal dentin, although the crystallites were significantly thicker in DI-II dentin 6.8 nm(s.d.=0.5) vs 5.1 nm(s.d.=0.6). The shape factor of the crystallites, as determined by SAXS, showed a continuous progression in normal dentin from roughly one-dimensional (needle-like) near the pulp to two-dimensional (plate-like) near the dentin-enamel junction. The crystallites in DI-II dentin, on the other hand, remained needle-like throughout. The above observations are consistent with an absence of intrafibrillar mineral in DI-II dentin.