I didn't really ever brush Jackson's teeth for the first 3 years of his life. He was a toothbrush hater for a long time. It was such a struggle that I had basically given up and managed only to brush his teeth when he'd get in the bath tub every week or two.
He had to have a dental last November due to another tooth issue (over-bite, had a vital pulpotomy on his canine tooth) so got them cleaned while under. They weren't
terrible but did have some tarter build-up on all of his canine teeth (enough to warrant a cleaning). Anyways now they are shiny and white and I plan on keeping them that way and hopefully not needing for a long time (at least that's my goal).
So anyways, after the procedure on his mouth, we weren't allowed to brush for two weeks so I took advantage and every night for those 2 weeks, we would go into the bathroom. First couple of days, he'd just go in there and get a treat. Then I brought out the brush, introduced him to it, let him sniff, etc. Eventually he had started opening his mouth when he saw it. I would lift up his lip, get him used to me touching around his face, etc, and he'd get a treat.
Now he's pretty good at getting his teeth brushed. He comes into the bathroom with me or I put him on my bed... (I always use a high value treat, like a piece of chicken) it's his little routine and he definitely doesn't like it (he tries to run away at first)... I wouldn't say he enjoys it but he tolerates it and that's what is important!
I bought CET beef flavored toothpaste which he seems to like so I think that helped too.
Oh, I also use petzlife about once every 3-5 days, we also have HealthyMouth so use that a few times a week, and I sprinkle some Prodent PlaqueOff on his food a few times a week too.
But it just took a little extra effort, and now it's not so bad.