1. Department of Oral Microbiology, Forsyth Dental Center, 140 The Fenway, Boston, Massachusetts 0211
2. Department of Oral Microbiology, Forsyth Dental Center, 140 The Fenway, Boston, Massachusetts 02115
3. Department of Electron Microscopy, Forsyth Dental Center, 140 The Fenway, Boston, Massachusetts 02115