I'm feeding my guinea pig (Nelson) Oxbow Cavy Cuisine and timothy hay (Kaytee brand), also veggies daily. However his molars are overgrowing and having to be trimmed. Twice in the past 2 weeks, and then 3 years ago. I've seen things such as cardboard tunnels stuffed with hay but didn't know if the cardboard would be safe for him. What in the United States can I get him to help with his teeth? Thanks 
