Hi have you tried some lint wrapped around your finger & some pet toothpaste gently massage his teeth & gums? NOT WHILE HE HAS GUM ETC PROBS, sometimes bad breath, teeth & gums may be a sign of other probs, take him to the vets they know best, I personally do not give biscuits to my cat as I feel it's like flossing with a digestive biscuit, & think they lead to kidney probs. hope Toby feels better soon,
good luck Baloo j.