Division of Oral Medicine and Dentistry, Brigham and Women's Hospital, Boston, MA, USA. Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, MA, USA. Blood and Marrow Transplant Department, Moffitt Cancer Center, Tampa, FL and Johns Hopkins All Children's Hospital, St Petersburg, FL, USA. Pediatric Hematology-Oncology, Stanford Medical Center, Stanford, CA, USA. Aflac Cancer and Blood Disorders Service, Children's Healthcare of Atlanta, Atlanta, GA, USA. Children's Oncology Group, Monrovia, CA, USA. Department of Preventive Medicine, University of Southern California, Los Angeles, CA, USA. Children's Mercy Hospital, Kansas City, MO, USA. Division of Haematology/Oncology, The Hospital for Sick Children, Toronto, Ontario, Canada.