Teeth cleaning product

I was at the Pet store this weekend and saw two products that say they will help with the cleanliness/health of your cats teeth and mouth (and improve breath). You're supposed to mix a little bit in with their water everyday. Has anyone used/heard of a product like this?

I use Logic gel, I buy it from a company in the UK

I just got some Logic and must try it on Gizmo. She's just back on her L-lysine minus the Factor CQ-10 so I'm taking it slow for now.

I recently got one from Petsmart...it's called Liquid Oral Care. You just put it in their drinking water. I have no idea if it's working or not though.