1. Department of Advanced Oral Sciences and Therapeutics, Division of Periodontics, School of Dentistry University of Maryland Baltimore Maryland USA
2. Department of Periodontics, College of Dentistry University of Iowa Iowa City Iowa USA
3. Hard Tissue Research Laboratory The University of Minnesota School of Dentistry Minneapolis Minnesota USA
4. Department of Oral Pathology, Radiology and Medicine, College of Dentistry University of Iowa Iowa City Iowa USA