The best thing you can do to look after your cats teeth is regular (daily) brushing. If started as a kitten this needn’t be a chore but should be an enjoyable time where you & your kitten interact. You need to take things very slowly to start with and give lots of praise so that you and your cat will start looking forward to your brushing sessions.
Remember, this should be fun for you and your cat. Keep sessions short and positive. Be sure to praise your cat throughout the process.
First, have your cat get used to you putting things in her mouth. Dip your finger in tuna water, chicken broth, or other liquid your cat may like. Call your cat with a voice that means "treat" and let your cat lick the liquid off your finger. Then rub your soaked finger gently over your cat's gums and teeth. After a few sessions, your cat should actually look forward to this and you can move on.
Now, place a gauze around your finger. (You can again dip it in the tuna water or other liquid.) Gently rub the teeth in a circular motion with your gauzed finger. Repeat this for the number of sessions it takes your cat to feel comfortable with this procedure. Remember to praise her.
After your cat is used to having the flavoured gauze in her mouth, you are ready to start with a finger brush. We need to get your cat used to the consistency of this so, let your cat lick something tasty off of the brush so she gets used to the texture.
Once your cat is used to the cleaning item you are going to use, you can add the toothpaste Pet toothpastes either have a poultry or malt flavour so your cat will like the taste. Get your cat used to the flavour and consistency of the toothpaste. Let your cat lick some off your finger and then apply some to your cat's gum line with your finger. Praise your pet. Now your cat is used to the toothbrush and toothpaste and you are ready to start brushing. Talk to your cat in a happy voice during the process and praise your cat at the end. At first, you may just want to brush one or both upper canine teeth (the large ones in the front of the mouth). These are the easiest teeth for you to get at and will give you some easier practice. As before, when your cat accepts having several teeth brushed, slowly increase the number of teeth you are brushing. Again, by making it appear to be a game, you both will have fun doing it.
It may take up to a month or more before you are able to brush your cats teeth properly but do persevere- it will be worth it when your cat has lovely teeth & fresh breath.