29. Jahrestagung der Deutschen Gesellschaft für Biomaterialien

Prof. Dr.

Chair

PD Dr.

Quantification of differences in the shape of 3D structures using computed tomography

Surface modification technologies

Abstract text (incl. figure legends and references) Introduction: The analysis of differences in the shape of 3D structures plays an important role in a large variety of studies. For instance in genetic modified mouse models the assessment if the modified gene causes a wanted or unwanted skeletal phenotype is important to predict the involvement of the gene in other pathways. To study other biological process acting on the skeleton such as the Dehnel effect, the skeleton of different specimens need to compared, which requires an analysis that removes the influence of the size of the specific animal from the analysis of the shape of the skeleton. Another typical task is the generation of facsimiles by 3D printing. Dependent on the used technology and the structure of the object to print, deformations and/or changes in the size can occur, which need to quantified by comparison with the original. Methods: We applied a variety of different computed tomography device ranging from synchrotron microCT to clinical CT scanners depending on the size of the specimens of interest. CT allows a rapid, easy and dimensionally stable assessment of the 3D structure of e.g. bone, teeth and other dense materials. Here we show results for the analysis of the Dehnel effect in shrews, the phenotyping of genetic modified mice and the comparison of 3D printed teeth facsimiles with CT scans of the original teeth. We combine methods of calculation of surface meshes, calculation of higher order shape descriptors, 3D registration, calculation of local distances between two meshes as well as different types of supervised and unsupervised classification schemes. Results: Using this general pipeline we were not only able to show clear differences between genetic modified mice (knock-out of the Discoidin Domain Receptor 1 and 2) but also to discover mild effects caused by the gene-dose effect in heterozygous mice, which were previously unknown. In addition, the analysis pipeline validated the known Dehnel effect in shrews (the shrinkage of the brain and brain case volume by up to 40% in winter) by clearly demonstrating a change in the skull shape predominately in the brain case region (Figure 1). Moreover, the analysis pipeline was successfully applied to quantify the differences in the root channel geometry of 3D printed teeth in order to establish working with tooth facsimiles for the education of dentist. Conclusion: We developed an analysis scheme based on CT data sets of hard-tissue specimens to analysis differences in complex 3D shapes which could be easily adapted to other use cases.

Short Talk

Post-Sectioning verification and spatial correlation of 2D histological slices with 3D CT-Scans through 3D printed phantoms

Abstract text (incl. figure legends and references) Introduction: Histological analysis of hard tissue is labor-intensive, destructive, and does not allow targeting regions of interest (ROI). We propose a novel workflow of microCT guided section for the generation of precisely positioned sequential histological sections through the inclusion of 3d printed phantoms. Materials &amp; methods: In addition to the classic histological workflow, three 3D-printed cone-shaped phantoms were embedded in combination with different tissue specimens in resin (Technovit 9100, Kulzer). After hardening, the blocks were scanned in a microCT (Perkin Elmer, QuantumFX) at a resolution of 80 µm. A priming cut is performed using a diamond bandsaw blade (Messner, CutGrinder Primus). The specimen is then further sectioned using a laser microtome (Tissue Surgeon. LLS Rowiak). Completed sections were imaged using a microscope (Zeiss, Axiovert 200 inverted microscope). Results: We developed a workflow for microCT-aided hard-tissue histology, based on the inclusion of external markers visible in both microscopic and CT imaging. After the cutting process, the resulting section was comprised of the 2D slice of the specimen as well as the ellipsis resulting from the cones. Through the geometric parameters of the ellipsis, computed with the histological image, we obtained the major- and minor axis and iteratively search for the optimal corresponding region in the 3D microCT-scan of the specimen. This process was conducted for all phantoms, thus allowing for the reconstruction and extraction of the digital twin of the cutting plane in the CT data. Conclusion: In our novel CT-aided workflow, we demonstrated a method to retroactively verify the position of the cutting procedure, thus allowing for the possible fusion of histology and microCT by overlaying corresponding CT slices and histological sections. The established geometrical correspondence could be proven beneficial when the color-coded, but to two dimensions limited histology is expanded through registration to a 3D context.

Individual implants of the hip joint and pelvis

Abstract text (incl. figure legends and references) Different causes can lead to significant defect situations in the area of the hip joint. Extensive bony destruction is caused by infections, also in the case of in situ orthopedic implants, tumor diseases (including metastatic osseous changes), injuries or their consequences after fractures of the pelvis and complications of orthopedic joint implants in the area of the hip joints. In extensive acetabular defect situations, reconstruction is not always successful using available costly revision implants. In these cases, extensive defect zones with poor bone quality are found for placement or anchorage of standardized revision implants. After an exact analysis of the bony situation and taking into account the soft tissue situation, it is necessary in special cases to consider an implant adapted to the defect zone and to consider and plan an analysis with regard to such a restoration option. Here, the possibilities of virtual, three-dimensional planning of operations are available. Computed tomography, 3D reconstruction and bone structure analysis are used to create a matrix that enables planning for an individually created patient implant. This is pre-discussed with the surgeon through planning steps, adjusted if necessary and transferred to production after approval. The costs for these implants, which are used in special cases, are very high and are discussed in advance with the responsible health insurance companies. The implantation of these prosthetic components, which are individually adapted to the defect situation, leads to the possibility of treating extensive bony defect situations in the area of the os ileum / acetabulum in the hip joint with a high benefit for the patient. Rapid mobilization with full weight-bearing is possible. However, these patient-specific special implants are reserved for exceptional cases of bony destruction.

Evaluation of additively manufactured titanium implant specimens using µCT

Implant associated

Additive manufacturing (e. g. 3D printing)

Abstract text (incl. figure legends and references) Introduction: Biomaterials have been an active area of research for decades, but there is still a need for new and optimized implant materials. In this context, optimized means that the materials exhibit high biocompatibility. This also applies to implant sites in the skull bone, where due to physiology and the high demand for patient-specific shaping, existing materials and manufacturing technologies often only partially meet the requirements. Objectives: The aim of this study is to evaluate the biocompatibility of titanium implants in a short-term animal experiment (with a service life of 3 months). Surface compatibility and structural compatibility of implants produced using two additive manufacturing techniques (SLM, EBM) will be investigated. Two established implant materials, conventionally produced (milled) titanium and Bioverit®, serve as reference implants. Materials and Methods: Basis oft he study are 3D-μCT image data of the explanted and plastic-embedded implants together with surrounding (bone) tissue. The available 3D image data from μCT scans are visualized, segmented, and analyzed using the 3D Slicer software. Various parameters, such as the distance between bone and implant (Bone Implant Distance, BID) and the percentage of direct contact between bone and implant material (bone implant contact, BIC), are quantitatively recorded. Additionally, other quantitative parameters of the bone surrounding the implant are analyzed. The morphometric, software-based HistoGap method is used for the quantitative evaluation of osseointegration of the tested implant materials. Results and Conclusion: Preliminary comparisons of the evaluation of EBM and SLM titanium specimens with conventional titanium and Bioverit after segmentation and suitable measurements show promising results regarding osseointegration. Further morphometric evaluation using the HistoGap software and a statistical analysis are the next steps in this investigation.

Prof. Dr. Dr.

Histological and histomorphometric evaluation of photodynamic active biomaterials for periodontal regeneration in a 12 month animal bone study

Tissue regeneration/regenerated medicine

Cell-material interactions

Abstract text (incl. figure legends and references) Background: Recently our group developed two polymeric biomaterials with photodynamic antimicrobial surface activity for periodontal regeneration. The aim of the present study was to analyse biocompatibility and osseointegration of these materials in an ovine bone model. Material and Methods: Urethane dimethacrylate (BioM1) and tri-armed oligoester-urethane methacrylate (BioM2) were substituted with a mixture of ß-tricalcium phosphate and mTHPC (meso-tetra(hydroxyphenyl)chlorin). Both materials were implanted in bone defects in the femur (n=16) and tibia (n=8) of 8 female domestic sheep. Bone specimens were harvested and histomorphometrically analysed after 12 months of implantation. Detailed information upon the size of biomaterial remnants, bone volume, soft tissue volume and bone-to-implant contact in a 250µm thick region-of-interest (ROI) around the implant was obtained. Results: After 12 months of implantation, remnants of BioM1 showed a mean square size of 17.4 mm² while 12.2 mm² was estimated for BioM2. Original defect size was 19.6 mm² at baseline. For BioM1 a total bone value of 30.3% and for BioM2 of 8.4% was estimated. A soft tissue volume of 3.3% was detected for BioM1 and 29.5% for BioM2. BioM1 showed a bone-to-implant contact of 81.9% in the femur and 56.2% in the tibia. In contrary, a bone-to-implant contact of 8.5% in the femur and 16.4% in the tibia was detected for BioM2. Further, BioM2 was affected by tissue encapsulation and inflammation. Conclusions: BioM1 shows favourable characteristics. Further studies that investigate the suitability of BioM1 for periodontal regeneration are needed.

Lecture hall 6

Short Talks 9

GEXOS – Experimental Osteology

Short Talk Session

Short Talks 9
GEXOS – Experimental Osteology

Appointment

Chair

Programme

Short Talks 9GEXOS – Experimental Osteology

Appointment

Chair

Programme

Short Talks 9
GEXOS – Experimental Osteology