It's athing called pica, I believe. A 'need' or desire to eat unedible things. Pregnant women get this--the dementia patients do too.
I don't know what to do but give them something better to chew on. They make a thing called "chewelry" which is used for helping babies who have oral fixations have something safe to chew on--also to break them of the binky habit. I wonder if your LO would feel the same satisfaction with those?
My 99-yr old aunt with advanced dementia will work on a plate of food but then sometimes start eating the napkin. I think it's because the dementia detaches them from what's real and what's not. They are imagining it is something other than TP. We just have to monitor her.
I don't know what to do but give them something better to chew on. They make a thing called "chewelry" which is used for helping babies who have oral fixations have something safe to chew on--also to break them of the binky habit. I wonder if your LO would feel the same satisfaction with those?