dentists are like most professionals, they make work to make money. only doing neccessary work is all very well and good, but 99% of neccessary work is the lowest paid stuff, and since they can do the better paid stuff in the same time, it makes sense for them to try and get the better paid work, or to be more accurate 'create' better paid work. (same as any profession)
i had a "clicky jaw", and i needed braces on my bottom teeth. i refused both even though my parents weren't happy that i said no. and guess what my teeth are perfect and my jaw fixed itself. if you do a bit of research you'll find most clicky jaws settle once the jaw has finished growing, and that can take up to 25 years. i was 24 when mine stopped clicking. teeth can also take a long time to sort themselves out. it doesnt mean you need a dentists help, nature has been doing it a very long time. if you have seriously buckled teeth then fair enough take advantage of modern medicine, but for most people its natural for your teeth and jaw to take many years to settle, just like the rest of your body.
before i started refusing things i had a dozen fillings and a very painful root canal, and i now wonder if i needed any of it, i never had any tooth ache and there were no signs of decay, not even anything worthy of a fissure seal. but when a dentist says you need a filling you get one. i wish i said no a lot earlier and a lot more often, maybe i'd have less silver in my mouth now.
then again maybe i'm just my usual paranoid sceptical self. dont get me wrong, i've had a lot of neccessary work done too, such as having 2 steel pins stuck in whats left of one of my front teeth so a ceramic cap could be fitted, before that they fell off twice a year. if you have a problem then go see a dentist.
in any situation where one person (dentist) has a knowledge advantage over another person (patient) its expected that a certain amount of taking advantage will occur. i'm not suggesting all dentists will, or even most of them, but many will. at least dont be afraid to ask for a second opinion if you have any doubts.
. I was expecting a sticker but never got one 
