A committee report is a longer letter that usually replaces the three letter of recs required by most schools. For some schools, even with a committee letter, you are still required to get one dentist to write a LOR.
A committee report only comes after going through a committee process in which you are interviewed by several people who don't know you (science professors, scientists from the local community, and dentists in the case of my committee letter at my school) These people then recommend on a scale of 1-10 how ready you are for dental school and send a letter to the committee advisor (usually the predent or prehealth advisor). The advisor then writes the committee letter based off your results and his or her personal knowledge of you and that letter replaces the LORs
At my school, we actually are still required to get the LORs, so we get a committee letter and still send out 3+ LORs. For some schools, they are fine with just getting the committee letter. Call the schools you are interested in and ask if a committee letter replaces all their LOR requirements before you decide to nix getting the LORs