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Development of miniaturised fibre-reinforced composite structures for ultrasonic-based decontamination of non-shedding surfaces within the human organism

Subject Area Biomaterials
Synthesis and Properties of Functional Materials
Plastics Engineering
Lightweight Construction, Textile Technology
Materials in Sintering Processes and Generative Manufacturing Processes
Production Automation and Assembly Technology
Dentistry, Oral Surgery
Term from 2015 to 2022
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 277550171
 
Final Report Year 2022

Final Report Abstract

Around 7 million root canal treatments are performed in Germany every year. Despite very good chemo-mechanical preparation methods, endodontic treatments can fail. A significant reason for this is residual bacteria that remain in untreated root canal sections of the complex branched root canal system and lead to infections. The specific histology of dentin favors bacterial infiltration. Disinfecting agents in combination with sonic/ultrasonic systems are therefore used complementarily to remove the bacterial biofilm in areas of the root canal system that are difficult to access. Current sonic/ultrasonic systems (metal, plastic) are of limited suitability for use in the root canal. With metal ultrasonic needles, there is a risk of instrument fracture or even perforation in narrow and highly curved root canals. Whereas plastic sonic needles appear more compliant, but have higher material damping, which can lead to lower cleansing performance. The overall objective of this interdisciplinary project was to determine whether ultrasonic needles could be designed using engineeringdental methods in form of a serial-analytical methodology that would contribute to high root canal cleansing success without dentinal damage. Methods for the acquisition of abstracted virtual root canal geometries had to be developed in order to define the required material conditions for ultrasonic needles and to perform simulation studies. Using non-destructive radiographic visualization methods (DVT, micro-CT) of root canal systems, parameterization of human root canals was possible. The virtually developed root canal models could be transferred into steel and dentin models. Using the root canals of different radii of curvature in the steel model, conventional sonic/ultrasonic needles could be tested for failure and deficiencies in a standardized manner. In parallel, it was possible to identify fabrication parameters for a novel ultrasonic needle, adapt a pultrusion system, conduct storage tests of potential FRP/high performance polymers and fabricate first FRP/high performance polymer miniature demonstrator structures. The miniature structures could be tested for failure and dentinal damage in comparison with conventional sonic/ultrasonic needles in a first-ever standardized CNC-milled bovine dentin model using a newly established method, 3D optical digitization, for tribological investigation. Furthermore, a protocol for bacterial colonization of a human root canal model with Enterococcus faecalis was established. For the first time, the penetration depth of vital and avital Enterococcus faecalis bacterial cells within the dentinal tubules as well as the reduction of bacterial colonization by different disinfecting agents could be demonstrated by fluorescence microscopy using 4,6-diamidine-2-phenylindole. For quantitative assessment of the cleansing degree of root canal systems, a method was established in which the bacterially contaminated roots were ground with a cryomill, the bacterial DNA extracted and quantified by qPCR. Using qPCR, it was thus possible to investigate the cleansing effect of the novel ultrasonic-needle-demonstrator and conventional ultra/sonic needles as well as disinfecting agents on the root canal system. In conclusion, it was possible to design and fabricate an ultrasonic PEEK demonstrator using engineering-dentistry methods, which showed comparably good cleansing results without damaging the dental hard tissues.

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