Is shoulder impingement then becoming a tear caused from my career as a dental hygienist?

Doubtful: I am sure your job utilizes your upper body, but I have worked with many hygenist for over 35 years some very active in many activities and never heard of anything like this. If it is related i would believe you would have a very poor posture problem and not what you would have been trained in training.

Ergonomics Problem: I suffered shoulder impingement from dentistry. It does not mean you need to find another line of work. Physical therapy helped strengthen the muscles around my shoulder to decrease the pain. I also learned to avoid carpel tunnel syndrome- another ergonomic problem in dentistry. Best of luck to you!