I always thought I'd be good at teaching dental assisting since I've done it so long. Every time we'd get a new assistant I'd look forward to first, teaching her the basics and then, once she had that down, moving on to the more intricate points that make an assistant really good. I felt it would be a pleasure to watch someone go from basically knowing nothing about it, to becoming proficient. The problem was, not many people have the patience to learn the boring stuff.
When a new assistant is being trained everything is new, exciting and a little bit scary. She depends on the person training her like a newborn depends on it's mother for survival. As she becomes more comfotable with the basics she doesn't want her trainer around as much anymore. Now you're in the terrible twos, which with a new assistant may occur around the 2-3 month mark. You could walk away and think "Ok, go for it.", but where would that get anyone? The problem is that it becomes a power struggle and the dentist is invariably drawn in, and as far as he can see the assistant is now able to suction good enough to get through a procedure, but if you leave it at that, this will not become a career assistant. She will get bored and see what she is doing as a job that works for now.
When you find someone who wants to learn and loves assisting the whole story changes. For your part, if you been through a lot training people who don't want to tolerate the process, you first have to get past your reluctance to invest yourself in this new person's learning. They have to be able to trust that you have their best interests at heart. You both have to realize that you are giving something that can't be found on a store shelf. You have to respect them for being willing to accept your training methods, and they have to respect the time, energy and effort it took for you to acquire your knowledge and your willingness to give it to them. Now, once you get past the newborn stage you have someone who wants to grow and that is when it becomes satisfying for both of you.
You know you've got that person when they get excited to the point of dorkiness about assisting. You start to get pretty excited and dorky yourself as you get pulled into their enthusiasm. You become devoted to their development and look forward to each new step in the process. As you teach them you learn. You learn new ways of looking at things and doing things that had become routine to you. You learn that helping someone else succeed is as rewarding as succeeding yourself. Their success is your reward for the effort, time and care you put into them and in itself is enough.