Loved one with dementia has new behaviors. Is this common with people who have dementia?

First... Check to make sure there are no dental issues that have caused this change. There may be mouth pain that they are trying to relieve by chewing on something soft.

My Husband chewed on just about anything.
I would cover his legs and lap with a blanket and he would bring it up to his chin and begin chewing on it. I have cloth napkins that are used and there are many that he chewed. I would give him a piece of cloth to chew on and if that fell from his hand he would begin chewing on his fingers.
I did find Baby teething rings that he would chew. Believe it or not some dog toys as well. The dog toys are sturdier than baby teething rings since dogs teeth and jaws have more PSI they tended to last longer.
He would also chew on his shirt collars. Funny thing is when his son was real little he would chew on his shirt collars and I would try to discourage it and my Husband told me he did the same when he was little.
So find something safe and soft for them to chew on if this is going to be a "thing".

And I have to comment or ask... Is your loved one is in Memory Care or Assisted Living? the concern that I would have with AL is your loved one could decide to leave the facility. It might be time to think about MC rather than AL

Is this a Memory Care facility? If not and if it continues, I’d explore Memory Care. There, there is more supervision of the person as well as prohibition of common non-food items that could prove harmful if ingested, like soap, toothpaste, deodorant, etc. At my LO’s MC the items are kept locked up, unless being used under supervision.

Oftentimes with dementia, especially fronto temporal dementia (FTD), the person reverts back to baby type behavior by putting everything they see or touch into their mouths. You really can't remove everything from her room, that's not realistic........and even if you did, she'd start sucking her blanket or her clothing. Obviously, your loved one must be watched very closely to avoid having a harmful thing go into her mouth & down her throat. Your loved one may need to have a sitter during the day to watch over her until this phase passes.........and hopefully it WILL pass.

In the meantime, there is a product called Chewelry which is 'jewelry' to wear that is intended to be chewed on; for people with disabilities who put harmful things into their mouths, here's something that ISN'T:

https://www.arktherapeutic.com/chewelry/?gclid=Cj0KCQjw2or8BRCNARIsAC_ppyZFnwhHeiancgp0iKMJotO24TFNolCrRM5u-16IyZqkmPCbs95_QWoaAoazEALw_wcB

Good luck!