One of my rats recently had to be sedated for tooth trimming because of inadequate chewing surfaces. He has one lower incisor with a defect such that it curves outward a bit and if not kept short, can quickly become a problem. Last time it got so bad the tooth was poking into his upper mouth causing an abscess that required treatment and antibiotics. Since then I have tried various chewing options including Willow balls and wreaths from the pet store, dried sea sponge and branches from a Persimmon tree. The latter is the best option so far, but still minimal chewing. This particular rat is extremely food-driven, so I'm wondering if perhaps rawhide or something else with a food or food-like component that is still firm enough to trim teeth, and completely safe for rats. His lower incisors are getting too long again and I simply cannot afford regular trimming under sedation at a vet. I need some suggestions for things to chew that are attractive to him and 100% rat-safe. Thanks!