title: Intrafibrillar mineral may be absent in dentinogenesis imperfecta type II (DI-II).
abstract: High-resolution synchrotron radiation computed tomography (SRCT) and small-angle x-ray scattering (SAXS) were performed on normal and dentinogenesis imperfecta type II (DI-II) teeth. The 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-angle diffraction peaks at harmonics 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-angle peaks were almost non-existent 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 [SD = 0.5] vs. 5.1 nm [SD = 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.
authors.affiliation: Department of Preventive and Restorative Dental Sciences, University of California, San Francisco 94143-0758, USA. jkinney@itsa.ucsf.edu
authors.forename: J H
authors.initials: JH
authors.lastname: Kinney
authors.forename: J A
authors.initials: JA
authors.lastname: Pople
authors.forename: C H
authors.initials: CH
authors.lastname: Driessen
authors.forename: T M
authors.initials: TM
authors.lastname: Breunig
authors.forename: G W
authors.initials: GW
authors.lastname: Marshall
authors.forename: S J
authors.initials: SJ
authors.lastname: Marshall
mesh_terms: D000293:Adolescent; D000328:Adult; D003094:Collagen / Q000737:chemistry; D003460:Crystallization; D003804:Dentin / Q000000981:diagnostic imaging / Q000473:pathology; D003811:Dentinogenesis Imperfecta / Q000000981:diagnostic imaging* / Q000473:pathology*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008964:Molar, Third / Q000473:pathology; D012542:Scattering, Radiation; D017356:Synchrotrons; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D003094:Collagen