PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact open-help@bu.edu.vi, 88 leaves : col. ill.Dissertation (DScD) --Boston University Henry M. Goldman School of Graduate Dentistry, 1995.Includes bibliography: leaves 77-87.