Some Questions About Dentistry in Korea / America

So I took a trip to the dentist to get my teeth cleaned yesterday. They call this 스켈링 in Korean, which judging from the word, probably was scaling originally. I imagine this was like 머플러 (muffler) which isn't what it sounds like since it was used by the Japanese and then brought over here, thus making muffler a scarf, and scaling a teeth cleaning. But maybe the name is more accurate than you would think. In Korea, they don't use a tooth pick to scrape plaque off, they use a little machine which scrapes for them while they hold it against the teeth. But this feels like they are scaling you teeth (as in taking off the outer layer of scales like you would on a fish). It is not pleasant. I never was overjoyed about going to the dentist before in the U.S., but it was not something I dreaded. However, this form of cleaning hurts, and more than that, it feels like its bad for my teeth. Anyone with dentistry experience who knows? Whenever I ask a dentist here, they say to only come once every year, which makes me wonder if it is kind of hard on your teeth.

On the upside, they do cover your face with a cloth, as shown above. This is much nicer than staring a dentist in the face the whole time (although my dental assistant was pretty, so it would not have been bad either). So I really wonder why they don't do that in the U.S. Granted either way the situation is not comfortable, but at least cutting off visual contact makes it a bit less uncomfortable.

Here is my question about dentistry: why do Koreans use a machine to clean the teeth and why do they not in the U.S.? Is the machine not FDA approved? Is it bad for your teeth? Like glasses and the machine Korean optometrists use to gauge your lens correction, is it just a tendency to shy away from technology that replaces people among U.S. dentists/doctors? Next Question: Why don't they ever take x-rays at the dentist office in Korea? I have been four times to three different dentists, and never once had x-rays done on my teeth. Do you need to ask for something different to get that, other than a scaling? Do you really not need an x-ray and U.S. dentists just do that as a precaution (the insurance overkill thing)? Because my dentists here always do tell me I don't have cavities, so they must be somewhat visible to the naked eye. Anyway, a few things to think about...