I would relax, if the schools you're applying to didn't require a dentist LOE, than you should be fine. However, I wouldn't say a committee letter is weighed more heavily than a letter from the shadowing dentist. You should have more than 100 hours shadowing a dentist or dentists. I got my 100 hours from the same general dentist and I have a feeling he was more passionate and wrote me the strongest LOE out of all my LOEs, granted I didn't take the committee letter route.