Hey man, no one is going to be able to "tell" you what your EC's should be. Obviously volunteering and dental experience are a neccessity, but if you have ample hours in those, then you should find things to do to make yourself more "well-rounded". Look a hobbies. Playing any type of musical instrument is good for manual dexterity, martial arts club (my school had one), and things like that. I even did some auto-detailing on the side...............anything that interest YOU, and would satisfy something on the app, whether it be manual dexterity, or some experience. Good luck.👍