basic teeth cleaning services at the dental place in Once train station - 40 pesos.
I live in Zona Oeste, where it's clearly much cheaper for dental work. I had a root canal and a tooth that was cut in half repaired, all for 500 pesos. I also had another chipped tooth repaired, and a protesis made for another 500 pesos. Get out of the expat enclaves and you will find very good dental at a fraction of the price.
In Liniers (a couple of years ago admittedly), I had two porcelain fillings done for 150 pesos total - and compared to the work I had done in the UK (ugly metal) they are great. The dentist here was offended (on my behalf) that the UK dentist had put the metal fillings in my mouth at all, and so he even replaced them for me, included in the price. I had paid a lot for those UK ones, but they also damaged my teeth. I am very happy with my budget dental work done here!