well, i have been a dental assistant before, and the doctor was usually aways behind. he was an endodontist so he would run into problems a lot because sometimes there are unseen problems until you actually open up the tooth. also, sometimes it would take a bit longer than anticipated to get a patient numb and he always made sure that a patient was fully numb before drilling. there were also occations where the anestesia would wear off and he would have to give more, which also added to the time overlapping. but i know the office manager who was the one responsible for schelduling sometimes fudged up. so its not always the doctors fault for being late, it could have been the front desk not schelduling properly. it could also be the assistants faults because they are responsible for setting up and cleaning the rooms. so if they haven't cleaned a room or set it up, then that delays things as well.