Is it safe to have cleanings at a school (dental hygiene not dental
school). I remember reading something about them being too aggressive
and not yet being able to feel the difference between the tooth and
tartar.

Would it be safer to have them do ultrasonic vs. manual. i.e. is
ultrasonic safer when done by hygienist students.

They mentioned that cleaning should be done every 3 months. Is this
true or a way for them to get more people on which to practice.

Do they need x-rays to do cleanings. They requested x-rays or want to
take them. Is this necessary?

Anything I should watch out for?

I had one quadrant done as they spent a lot of time doing the initial
intake and measuring pockets etc...

Is cleaning around crowns done differently in any way.

I have 2 crowns which are uncomfortable. Gums appear inflamed around
them. The hygienist used the term 'fibrotic'
and thought I should floss the 'back teeth' 2 x a day and use a tooth
brush with a very small head to gently brush around the gums at those 2
crowns.

Thanks