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

Abstract

High-resolution synchrotron radiation computed tomography (SRCT) and small angle xray 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 enamel; donors were female and ranged in age from 18-21y. The DI-II specimens, which were also unerupted with intact enamel, 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-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 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.

Mechanical properties of mineralized collagen fibrils as influenced by demineralization

“…In Dentinogenesis Imperfecta type II (DI-II) dentin, which lacks intrafibrillar mineral, there is approximately 67% of the normal mineral level. (Kinney et al, 2001b(Kinney et al, :2003. Prior work on demineralization of dentin showed the development of a shoulder in the mineral profile, which is consistent with retention of about 35% of the mineral in the intrafibrillar compartment (Kinney et al, 1995), although this was not the original *Corresponding author E-mail: gw.marshall@ucsf.edu.…”

Matrix Metalloproteinases and Other Matrix Proteinases in Relation to Cariology: The Era of ‘Dentin Degradomics'

“…Intrafibrillar mineral has the major role in dentin mechanical properties [Kinney et al, 2003;Balooch et al, 2008;Bertassoni et al, , 2011. Dentinogenesis imperfecta type II (DI-II) dentin lacks intrafibrillar mineral, with approximately 33% less mineral than normal dentin [Kinney et al, 2001[Kinney et al, , 2003]. However, the relative reductions in elastic modulus (74%) and hardness (76%) of DI-II dentin compared to normal dentin indicate the importance of intrafibrillar mineral, which stiffens the collagen fibrils, to the dentin mechanical (elastic) behavior under load [Kinney et al, 2003].…”

Isolated dentinogenesis imperfecta and dentin dysplasia: revision of the classification

“…High-resolution synchrotron radiation computed tomography and small angle X-ray scattering showed anomalies of shape and thickness of crystallites. 37 A candidate gene for DGI-II was identified on chromosome 4q21 by linkage analysis between markers D4S2691 and D4S2692. 38 Xiao et al 28 described the first mutation in association with the disease.…”