Advanced Microscopy Solutions for Dental Research

X-ray Computed Tomography (CT) techniques have opened the door to the non-destructive study of materials' internal microstructure with wide applications across multiple disciplines. ZEISS X-Ray Microscopes (XRM) have incorporated synchrotron technology to provide high resolution and good contrast for 3D imaging of internal microstructures, resolving features from sub-micrometre down to tens of nanometers length scale. The unique ZEISS XRM technology has enabled many advanced analytics features for materials science research. ZEISS XRM's two-stage magnification architecture allows a high-resolution scan to be maintained across a large working distance, which is technically impossible with a conventional geometric magnification-based CT system. This feature is known as the Resolution-across-a-Distance (RaaD). The RaaD feature enables in-situ testing and time-lapse 3D scans with unprecedented imaging quality for direct observation of material as they are exposed to a stimulus such as a load or thermal stress. 

Bone grafts are in huge demand globally for bone restoration and alveolar augmentation. Currently, autogenous bone is considered the gold standard for bone grafting, but harvesting bone from another location of the same patient implies additional surgery and risks. Xenografts and allografts are used as alternatives but they pose risks of disease transmission and adverse reaction. To address these limitations, NDCS combined a 3D-printed bioresorbable polycaprolactone tricalcium phosphate (PCL-TCP) scaffold with adipose-derived mesenchymal stem cells (AD-MSCs) harvested, processed and implanted at the time of surgery. Using a porcine model, we proved that the addition of AD-MSCs into the PCL-TCP scaffold improved bone formation in the defect area, compared to the scaffold without cells. Next, we aim to improve the procedure by incorporating additional components to the PCL-TCP scaffold to increase the bioactivity and osteogenic differentiation potential of the scaffold. Together with our A*STAR collaborators and commercial partners, the NDCS team has developed a novel combination scaffold with a proprietary coating of minerals and biological mediator to improve the proliferation and osteogenic differentiation of the seeded AD-MSCs. We tested the novel scaffold in a mini-pig alveolar defect model pilot trial. Using the advanced ZEISS Xradia 620 Versa X-Ray Microscope, we managed to observe enhanced bone formation and reduced bone resorption in the AD-MSC-seeded novel scaffold.

Biomaterials research frequently involves biomimetic materials that are soft, non-conductive or beam sensitive in nature. When imaging such beam-sensitive or soft materials, it is often necessary to employ low accelerating voltages to prevent material damage. However, reducing accelerating voltages or beam currents typically results in poor image quality and low resolution. On the other hand, while surface coating reduces the charging effect on non-conductive materials, it covers the surface feature of the sample and result in the loss of surface details. In this presentation, we will highlight ZEISS FE-SEM technology featuring beam booster, smart autopilot, and nanotwin lens. These technologies collectively reduce the spread of primary beam, minimize the effect of lens aberration and ensure excellent detection efficiency to support high resolution imaging at low or ultra-low kV without the need for surface coating. Application examples that utilize low to ultra-low kV imaging of beam sensitive and non-conductive biomaterials such as gelatin scaffold and bioinspired materials will be provided for reference.

Bioinspired ceramic microstructures have the potential to fulfil combined unusual properties such as local anisotropy and hardness and bulk strength and toughness, but their current fabrication methods remain challenging. Here, we report a rational design strategy to fabricate dense bioinspired ceramics with complex microstructures that have tuneable mechanical properties and are sintered within minutes. This strategy combines a colloidal directed assembly, i.e., magnetic assisted slip casting (MASC), with templated grain growth (TGG) using pressureless ultrafast high-temperature sintering (UHS). The hierarchical microstructural designs result from the local orientation of alumina micro-platelets coated with Fe3O4 nanoparticles dispersed in a matrix of alumina nanoparticles. We show proof-of-concept ceramic structures that have horizontal, periodic and graded variation of local mechanical properties. Moreover, the microstructure can be tailored as per the requirement for bulk mechanical properties with values of strength and toughness reaching~200 MPa and ~10 MPa.m0.5, respectively. Furthermore, due to the tailorability of properties as well as shape flexibility, this fabrication strategy can be extended to creating dental implants mimicking the enamel and dentin layers without a distinct interface in between. This demonstrates the potential of the fabrication method to create strong and tough ceramic structures in time-saving and energy-efficient ways, opening a new design space for achieving locally tuneable complex microstructures.