1. University of Iceland, Vatnsmyrarvegi 16, IS 101 Reykjavík, Iceland;
2. Institute of Dentistry, University of Helsinki, and Department of Oral and Maxillofacial Diseases, Helsinki University Central Hospital, Finland; and
3. University Hospital, Reykjavík, Iceland, and Department of Gastroenterology, St. Joseph’s Hospital, Hafnafjördur, Iceland