History and development of plastination techniques.

Plastination was a game-changing invention for macroscopic anatomical preparation. The method yielded dry, odourless, tangible and durable specimens which allowed new exhibition and teaching set-ups and paved the way for sophisticated preparations and spectacular positioning of specimens. Despite the impact of the new method, there have been similar techniques in place before. Exsiccation techniques, polymer embeddings and specimen impregnation with hardening substances were earlier methods which already included the main concepts that were later combined and refined in plastination. S10 silicone plastination, the technique most commonly known and applied, was followed by plastination methods suitable for research and sectional anatomy teaching. Numerous variations of sheet plastination techniques allow research applications and new ways of presenting topographic relations and mesoscopic insights. Besides the development of plastination techniques in sensu stricto, related techniques had a renaissance with new applications and developments, including corrosion casting and diaphonization methods. This brief review shall provide a historical context of plastination including some anecdotal spotlights on the ideas and innovations that lead to nowadays plastination techniques.

Ultra-thin sectioning and grinding of epoxy plastinated tissue.

With classical sheet plastination techniques such as E12, the level and thickness of the freeze-cut sections decide on what is visible in the final sheet plastinated sections. However, there are other plastination techniques available where we can look for specific anatomical structures through the thickness of the tissue. These techniques include sectioning and grinding of plastinated tissue blocks or thick slices. The ultra-thin E12 technique, unlike the classic E12 technique, starts with the plastination of a large tissue block. High temperatures (30-60°C) facilitate the vacuum-forced impregnation by decreasing the viscosity of the E12 and increasing the vapour pressure of the intermediary solvent. By sectioning the cured tissue block with a diamond band saw plastinated sections with a thickness of <300 µm can be obtained. The thickness of plastinated sections can be further reduced by grinding. Resulting sections of <100 µm are suitable for histological staining and microscopic studies. Anatomical structures of interest in thick plastinate slices can be followed by variable manual grinding in a method referred to as Tissue Tracing Technique (TTT). In addition, the tissue thickness can be adapted to the transparency or darkness of tissue types in different regions of the same plastinated section. The aim of this study was to evaluate the advantages of techniques based on sectioning and grinding of plastinated tissue (E12 ultra-thin and TTT) compared to conventional sheet-forming techniques (E12).

Multiple polymer plastination: Combining different types of polymers in teaching and exhibition plastinates.

Vacuum forced tissue impregnation is the signature step of the plastination process. It requires polymers with a low vapour pressure, low viscosity and a long pot life. Plastination polymers are a compromise between these mandatory requirements on the one hand and various secondary demands such as specimen stability, resistance to UV light and defined light refraction index on the other hand. Combining different polymers in one plastinate instead of using one plastination polymer alone can result in improved specimens for exhibitions and teaching including hands-on use for students. The aim of this study was to assess the range of possible sheet plastinate modifications and how the resulting multiple polymer plastinates can fulfil the secondary requirements of user-friendly plastinates. Adding sub-steps of tissue impregnation and processing to the standard plastination protocol allows combining different polymer properties including the use of substances which are not suitable for conventional plastination as such but have better properties than plastination polymers. Advantages like resistance to UV light and mechanical stability can be combined and characteristic disadvantages of plastination polymers can be avoided. Acrylic protection layers (APL) offer a complete protection of the specimen in combination with advanced presentation possibilities and the option of completely refurbishing valuable specimens. Hybrid sheet plastinates provide lower preparation cost and polymer-tissue interactions for an improved visualization of fat, nerves and brain tissue. Selective impregnation is a promising approach for the clearer differentiation of various structures and tissue types.

Corrosion casting in anatomy: Visualizing the architecture of hollow structures and surface details.

Corrosion casting is the technique by which a solid, negative replica is created from a hollow anatomical structure and liberated from its surrounding tissues. For centuries, different types of hardening substances have been developed to create such casts, but nowadays, thermosetting polymers are mostly used as casting medium. Although the principle and initial set-up are relatively easy, producing high-quality casts that serve their intended purpose can be quite challenging. This paper evaluates some of the more popular casting resins that are currently available and provides a step-by-step overview of the corrosion casting procedure, including surface casts of anatomical structures. Hurdles and pitfalls are discussed, along with possible solutions to circumvent them, based on personal experience by the authors.