1. Department of Periodontology and Dental Implantology, Faculty of Dental Medicine, Medical University of Varna, 9002 Varna, Bulgaria
2. Department of Clinical Medical Sciences, Faculty of Dental Medicine, Medical University of Varna, 9002 Varna, Bulgaria
3. Department of Oral Surgery, Faculty of Dental Medicine, Medical University of Varna, 9002 Varna, Bulgaria