1. Department of Pediatric Dentistry, Baylor College of Dentistry, 3302 Gaston Avenue, Dallas, Texas 75246, Department of Pediatric Dentistry, School of Dentistry, Hokkaido University, Sapporo 060, Japan
2. Department of Pediatric Dentistry, Baylor College of Dentistry, 3302 Gaston Avenue, Dallas, Texas 75246
3. Department of Dental Materials, Baylor College of Dentistry, 3302 Gaston Avenue, Dallas, Texas 75246