1. Department of Fixed Prosthodontics, University of North Carolina, School of Dentistry, 302 Brauer Hall, CB 7450, Chapel Hill, North Carolina 27599-7450
2. Department of Endodontics, University of North Carolina, School of Dentistry, 302 Brauer Hall, CB 7450, Chapel Hill, North Carolina 27599-7450, Department of Endodontology and Oral Diagnosis, Faculty of Odontology, Gothenburg University, Box 330 70, S-400 33 Gothenburg, Sweden
3. Department of Endodontics, University of North Carolina, School of Dentistry, 302 Brauer Hall, CB 7450, Chapel Hill, North Carolina 27599-7450