For training I would always use 'special' treats like sausage or chicken, and use LOTS of treats, generally I think people don't reward often enough when they are training. If you look at the video of Jean Donaldson (one of my favourite trainers) teaching a dog to accept a Gentle Leader and see how often she gives treats you will see she uses a very high reward rate, literally feeding one treat after another when she's teaching a new behaviour or something the dog finds difficult:
I don't think you have to worry too much about her teeth if you aren't using bought treats with lots of artificial flavourings etc, but keep an eye on her total food intake - if she's had a lot of training treats give her a little bit less in her meals. Also training treats can be very small, generally dogs will work just as well for a tiny bit of chicken as for a larger bit
With the ball, you could try having two identical balls so you throw one, then when she brings it back you get her interested in the second one which you throw when she drops the first and so on.
