Best at home plaque reducing toothpaste

I rescued a senior dog in 2018 and he's had TWO teeth surgeries and his few remaining teeth already have a lot of plaque build up. I am 99% sure this just stems from a lifetime of dental neglect at the shelter.

I don't want him to have to go for a third surgery. He's 13 years old and has extreme anxiety, he does not do well being left (the last time he was there the vet had to sedate him because he wouldn't stop howling and howling and making ALL the dogs howl along). The last time I took him, I noticed the plaque starting to build up VERY soon after his surgery.

So I'm looking for a better toothpaste than what I'm currently using. I brush his teeth several times a week and spray colloidal silver because I don't want periodontal disease. He gets three biscuits a day for breakfast and then chunks for supper with some home cooked soft food. He also gets dental treats. None of my other dogs have these kinds of teeth issues.

Does anyone have a good recommendation?