Atlas of Foreign Materials
It is marketed as Aquamid. It is a permanent filler material used for soft tissue augmentation. It is not approved for sale in the United States but can be purchased on-line.
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Polyacrylamide gel low power
Polyacrylamide gel medium power
Polyacrylamide gel med-high power
Polyacrylamide gel high power
Images courtesy of Scripps Oral Pathology