By clinical experience I mean any experience that exposed oneself to the clinical side of healthcare (e.g. working in an environment where you have contact with patients, specimens, lab, or human tissue). During my freshman year I used to work in the blood lab for about 20-25 hours a week all the way through my sophomore year and almost full time during summer's and winter vacations.Other experience I have was working as a lab assistant in vascular surgery, neurological surgery etc. if you multiply 20 hours/week x 40+ weeks that is 800 hours times two. I had around 1,600 hours working with bodily fluids and human tissue. I hope this clarifies your question. Also, I was working graveyard (3:00 am - 7:30 am) then went to class.
DesiDentist
Also, I wasn't observing but assisting most of the time. I didn't get paid for any of my dental experience though. I observed when I just started out. I would highly recommend working one on one with a dentist and get the experience. There is nothing interesting about sitting in a corner and just randomly looking around in the room. You should push yourself to get a "feel" for the career you are about to embark on.