Short Communication
Nanostructure of healthy and caries-affected human teeth

https://doi.org/10.1016/j.nano.2011.09.005Get rights and content

Abstract

Spatially resolved small-angle x-ray scattering based on synchrotron radiation combines the quantitative assessment of nanometer-sized components using scattering with the real-space imaging by means of scanning. The method enables us to study the effect of caries-induced damages on the inorganic and organic nanoscopic components in human teeth. We demonstrate for several 200- to 500-μm-thin tooth slices that the bacterial processes dissolve the ceramic components in enamel and dentin, but the dentinal collagen network remains practically unaffected with respect to its abundance and orientation in early stages of caries and in parts of extended carious lesions. Consequently, we speculate that future caries treatments can be developed reversing the effect of bacterial attacks by means of suitable remineralization of the dentin.

From the Clinical Editor

In this groundbreaking study of caries pathology using synchrotron-based X-ray scattering, the authors demonstrated that while bacterial processes do dissolve the ceramic components in enamel and dentin; however, the dentinal collagen network remains unaffected, enabling the development of future caries treatments that re-mineralize the dentin.

Graphical Abstract

The scattering pattern related to the 67-nm signal shows abundance, degree of anisotropy, and orientation of the nanostructures between 57 and 69 nm according to the color wheel. Comparing the spatially resolved collagen-related signal with the total scattering signal of the early stages of caries in human dentin, the authors find that the ceramic parts are affected, but the collagen is unchanged, which may have an important impact on the development of future dental treatments of carious teeth.

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Section snippets

Methods

Eight teeth, five carious and three healthy, were extracted for clinical reasons and cut into 200- to 500-μm-thin slices parallel to the tooth's long axis with a diamond band saw (Exakt Apparatebau GmbH, Norderstedt, Germany). The slices of the teeth were stored in phosphate-buffered saline (PBS). Only one slice from the healthy teeth was stored in air.

Synchrotron radiation-based micro computed tomography (SRμCT) measurements were performed at the beamline W 2 (HASYLAB at DESY, Hamburg,

Results

The organic ingredients of dentin contain mainly collagen-I fibrils. The building blocks of collagen arrange themselves along the collagen fibril with a main periodicity of 67 nm, as determined, for example, by means of atomic force microscopy and SAXS.17, 18

Figure 1 shows, in the top row, a typical scattering pattern from healthy dentin and the corresponding radial-integrated intensity (q-plot). A distinct peak, associated with collagen-I, is found at the q-values between 0.091 and 0.111 nm-1,

Discussion

The scanning SAXS images of human teeth show similarities to polarization microscopy pictures obtained from tooth slices many decades ago.23 The preparation of the tooth slices for polarization microscopy, however, is much more laborious. The slices have to be thin enough for the optical transmission and their surfaces have to be well prepared to avoid artifacts. Because the photon energy can be adapted to the slice thickness in scanning SAXS, much thicker tooth slices can be investigated,

Acknowledgments

The technical support of F. Schmidli (Basel) for the tooth preparation and of Xavier Donath during SAXS measurements is gratefully acknowledged. Extracted teeth were kindly provided by Dr. Marlen Luckow, Dr. Gabriel Krastl and Prof. Dr. Nicola Zitzmann. The SAXS experiments were performed on the cSAXS beamline at the Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.

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