I did 85 hours and was accepted, however some schools felt it wasnt enough and as a result they didnt accept me. For example, the first question I was asked at a certain interview was.."so you haven't done any shadowing since your freshman summer..." I tried to talk about all the other things I had been doing, community service, volunteer teaching, but this guys wasnt having it, lol. In fact, after I described my activities, he retorted with, "but you haven't done any shadowing". Another school sent me an email asking me if I had done any more shadowing since submitting my application, I had to respond no and as a result didn't get an interview.
I do agree with the other responses describing the value of shadowing as understanding the daily activities of the dentist, moral dilemmas, knowledge of what a daily routine is, and that what one learns from shadowing can definitely plane off after so many hours. The reason I never sought more opportunities was simply because I felt I had a good base of knowledge as to what a dentist's day is like after 85 hours spent shadowing and doing various tasks in his office, and as a result was able to make an educated choice in pursuing dentistry. However for some dental schools they either just need another variable to analyze you with or they see a greater value in shadowing.
Another view is that they want to see your sooooo interested in dentistry that nothing can keep you away from an office and therefore they expect to see constant shadowing throughout college.
My personal view on shadowing is that, with too many hours, it can produce a sense that the student knows more than they really do. For example, a while back another pre-dent was glad to brag that he could fill a cavity after repeatedly watching the dentist do it. Such a sense of overconfidence could translate into botched procedures during dental school as the student neglects to follow the steps laid out by the professor, because he thinks he already knows them after shadowing.
Of course something like this is not the norm, and it's great to have a basic knowledge of the most common procedures.
In the end, although shadowing can only teach you up to a certain point, if two applicants with similar stats and qualifications are put side by side, who will they pick? the one with 100 or 1000 hours of shadowing? When you look at it this way the excess hours definitely could be seen as translating into a greater interest in dentistry. If I could go back I would definitely do more shadowing, just to be on the safe side.... Its their game, we might as well play it