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Integrative X-ray techniques for chemical and structural characterizations of dental interzones

Dental treatment includes restoration of degraded tooth tissue with artificial non-degradable materials with the aim of achieving long-lasting mechanical and aesthetic durability. Inevitably a thick interface (interzone) is formed between healthy tooth tissue and dental restoration. We identify the transition region between filling and tooth tissue as a distinct region that we henceforth name 'dental interzone', where composition is different from both the filling and dental tissue that comprise the filling. Thus, dental interzones comprise complex micro-geometries and chemical gradients, between a variety of dental materials and the hierarchical structure of natural hard tissues such as enamel or dentin. Degradation in such interzones is often the reason for restoration failure and a need for retreatment.

In dental research there have been limited methodological studies on material composition instability, ageing and changes and effects on the immediate vicinity of interzones between filling and tooth substrate. Tracking of dynamic degradation in the juxtaposed materials is challenging, as they differ in main constituents (light elements prevail in the natural tooth tissue, whereas heavy elements are typical for fillings), density and structure. The aim of this project is to advance a multi-modal quantitative imaging methodology adapted to dental interzones by coupling synchrotron X-ray refraction radiography (SXRR) and tomography (SXRCT) as well as micro X-ray CT imaging (μXCT) with micro-X-ray fluorescence (μXRF) in 2 and 3 dimensions. For this purpose, the used methods will be adapted to the objects of investigation, the 3D data sets will be coupled (registered) and quantitative considerations including uncertainty evaluations will render the methodology into a true analytical tool.

This development will pave the way to mapping tooth restoration failure and help understand predictable changes close to and around the interzones between dental tissue and artificial filling material. This is an important step towards controlling unwanted chemical and structural/density degradation and might become a new standard methodological instrument in dental research. The ultimate goal in the future is to support and enhance clinical treatment procedures.

IXdent is a joint project funded by the german science foundation between TU Berlin, HZB and additionally Dr. Bernd Müller from the Bundesanstalt für Materialforschung und -prüfung (BAM) and Dr. Paul Zaslansky from the dental clinic of the Charite in Berlin.