I'm going to start off with the caveat that I can give a very limited and narrow view on this. I'd love it if someone else can chime in with a broader view.

Well, from what limited experience I have with the topic, toothpaste/tooth powder was a pretty new invention. It's my understanding that dental hygiene wasn't as bad as we suppose today. I recall reading that in the American South, it was pretty common for people to clean their teeth with willow twigs, which have some sort of natural antibiotic.

I did read an article the other day in the course of my thesis research where a dentist urged schools in Arkansas to teach children how to brush their teeth. He wrote that "a child cannot give attention to studies if the mind is diverted to aching teeth." In Arkansas at least, improving the health of rural students was a big focus among politicians and educators. Teaching proper dental hygiene was one way that they hoped to accomplish that, along with hookworm eradication campaigns, getting children to wear shoes, and so on. Teaching basic dental hygiene was adopted without controversy in Arkansas schools in 1916, so I think it's safe to say that ordinary people were okay with tooth brushing. The expense of buying a toothbrush and tooth powder was probably the limiting factor. When you're a poor tenant farmer, you're not likely to run out and buy stuff to take care of your teeth when you have to afford food for your family.

Dr. Elbert Stewart, "The Oral Hygiene Movement", The Arkansas Teacher, vol. 1 no. 5 May 1913, 3-5