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I'm thinking it's actually none of the above, since Glasgow Grin is a permanent smile, and Slasher Smile and Cheshire Cat Grin have to do with intent. It looks like the character can have different mouth expressions... it's just that the teeth are always visible. I don't think there's any specific trope for that. Except maybe depending on how you feel about it, it could be Nausea Fuel?
I'm not sure if this fits under Glasgow Grin, Slasher Smile or Cheshire Cat Grin. A character in Goblins has transparent skin around his mouth, meaning his teeth are always visible.