How are people dealing with dental hygiene issues?

Mom went to the DDS for a routine visit; she'd not been for maybe 6+ months, but less than a year. Told she has 13 cavities and while she had previously been meticulous about brushing/flossing, obviously she is no longer. The DDS is actually our next door neighbor whom she recognizes and she is accepting of the care for now. I have found him to be a bit of a clueless pain, in spite of the fact that his own mother is in a nursing home with dementia. His thoughts were to encourage /coach mom on brushing after every meal. I am not going to break the news to him that the reality is mom is a grazer. She is able to feed herself and eat what and when she wants and I am grateful for that. She is going to reject my efforts; and she is likely to get pissy at dad if he attempts to remind her to brush. I have seen the Teepa Snow video...and have read (though this DDS didn't have much faith in the benefit of it) that more frequent cleanings might help. My thought is it would at least keep decay from spreading/worsening if she goes in every 1-2 months for a cleaning. I read about trying to get them some fruit salad at the end of a meal (the acid supposedly helps to get rid of the plaque??) or to snack on things like fruits and veggies. To that end I cut up and made a container (since she thinks everything is hers anyhow) of celery sticks and radish slices. She really did a number on that...and I found the bowl on the counter, with the bottle of soft drink beside it LOL. But as far as the soft drink goes, I'm glad she's drinking as she doesn't do much of that for hydration. She's 97 with "mixed type" dementia.