What type of embedding medium has been introduced for electron microscopy?

The introduction of polyester plastic, specifically EPON, as an embedding medium for electron microscopy is significant due to its ability to provide better structural integrity and resolution at the ultrastructural level. Unlike paraffin wax, which can be used for light microscopy but lacks the necessary density and clarity required for electron microscopy, EPON allows for the preservation of fine cellular structures that can be visualized using electron beams.

The high plasticity and reduced viscosity of EPON during the embedding process enable detailed infiltration into tissues, ensuring that even the smallest anatomical features are well preserved. This is crucial for studies requiring high magnification and detailed examination of cellular components, such as organelles or intracellular processes, which is a critical aspect of histopathologic analysis using electron microscopy.

Additionally, traditional embedding mediums like paraffin wax and xylene are not suitable due to their properties that do not support the high-resolution imaging demands of electron microscopy. Bioloid, while mentioned, does not have the established utility and advantages when compared to EPON in this context. Therefore, polyester plastic, especially in formulations like EPON, is the preferred choice for preparing samples for electron microscopy, ensuring optimal visibility and detail in histopathologic evaluation.