Which impression material is unsuitable for taking the working impression for a ceramic crown construction?

Alginate is considered unsuitable for taking working impressions for ceramic crown construction due to its limitations in accuracy and dimensional stability. While alginate is commonly used for preliminary impressions because it is easy to work with and relatively inexpensive, it is not ideal for situations requiring high precision, such as crown and bridge work.

For ceramic crowns, the working impression needs to capture fine details and maintain dimensional stability over time, especially since the impression will be used to create a precise dental restoration. Other materials like addition silicone, condensation silicone, and polyether are designed to provide the required accuracy and stability. They can capture details with far greater fidelity and will not distort significantly, making them more suitable choices for producing a working impression in the context of crown construction.