They meticulously showed me why cavities form and which spots I don't brush well by applying a dye to my teeth

They applied a dye to my teeth to meticulously show me why cavities form and which areas I don't brush well, and taught me how to brush properly from the basics, which I really appreciated.
I think it was the head director, and the anesthesia for the cavity treatment was done so well that it didn't hurt at all, and even though it was the weekend it finished quickly, so I was grateful.