I've been brushing my kitty's teeth for over a decade and she only needed to have her teeth professionally cleaned 1x in her life.
A few tips:
Start very slowly. Every day while you pet Bella, just rub the side of her mouth once. Then continue petting her.
Every day put your finger in a little longer and further alongside her gumline til she is used to that. This is just to get her used to getting touched there.
Once she is used to you touching her gums, she will be ready for the brush. Get an Oral B baby toothbrush -- has Sesame St characters on it
. Then get her used to the feel of the brush by introducing it slowly as you did with your finger -- no toothpaste yet.
Once she is used to the brush get some kitty toothpaste at the pet store -- the Petrodent tastes malty, my cat thinks it tastes yummy -- then start using the brush with toothpaste.
Always end these sessions with praise and love and a treat.
At any time your kitty begins to show signs of being uncomfortable, stop before it turns into a struggle. Accomplish the one thing you want to do dentalwise for the day then give a treat. You don't want to turn this into a battle -- nor do you want kitty to think that if she wiggles long enough, she can get away with anything.
My 11 year old Russian Blue has had her teeth brushed since she was a baby so now she looks forward to it and begs to have them brushed -- NOT because she thinks having a big ol brush in her mouth is nice but she knows she gets a treat! LOL
Good Luck on the pearly whites!