1. Aachen University; Germany
2. School of Health and Society; Kristianstad University and DRSK Development AB; School of Health and Society; Kristianstad University; Sweden
3. Department of Oral and Maxillofacial Surgery and Department of Periodontology and Oral Biochemistry; VU University Medical Centre and Academic Centre for Dentistry Amsterdam; Amsterdam The Netherlands
4. VU University Medical Centre and Academic Centre for Dentistry Amsterdam; Amsterdam The Netherlands
5. Department of Conservative Dentistry; Aachen University; Germany