Dr. Peter Wetselaar, MSc, PhD, dentist and specialist in functional diagnostics and therapy of CMD and tooth wear, Chair in the Department and Clinic of General Dentistry, Academic Center for Dental Medicine Amsterdam (ACTA), Amsterdam/Netherlands

As one of the world's most recognized prosthodontists and ceramists, Dr. Winter teaches dentists in Spear Workshops to understand the interdependence between laboratory procedures, treatment planning, restorative techniques, materials and laboratory procedures.

In addition to teaching, Dr. Winter produces Spear Study Club modules and creates a variety of clinical content for the Spear learning ecosystem. He has taught more than 900 didactic, clinical and technical courses in more than 40 countries. For the past 36 years, he has maintained a private practice limited to prosthodontics, and currently practices in Newport Beach, California. He is co-founder of Esthetics by Design dental laboratory and is past president of the American Academy of Esthetic Dentistry.

Dr. Winter graduated in 1981 from Marquette University School of Dentistry and completed his prosthodontic specialty residency at the VA Medical Center in Milwaukee in 1983.

Since 1988, Siegbert Witkowskihas been working as Chief Dental Technician in the Department of Prosthodontics, University Hospital of Freiburg, School of Dentistry (Chair: Prof. Dr. B. Spies; Chair until 2016: Prof. Dr. Dr. h.c. J.R. Strub). He earned his diploma in Dental Technology from an apprenticeship program in Hannover, Germany. He did postgraduate studies and gained work experience at the following institutions: University of London, Royal Dental Hospital (1983-1984); University of Zürich, School of Dentistry (1984-1986); University of Southern California, School of Dentistry (1986-1988). Mr. Witkowski was certified as a Dental Technician (CDT) by the National Board of Certification of Dental Laboratory Technology (USA) in 1986. In 1991, he earned the diploma of the German Master Dental Technician from the master school in Freiburg, Germany. Siegbert Witkowski was co-editor and -founder of the German journal „Implantologie” [Implantology] (1993-2000). For the monthly journal „Quintessenz der Zahntechnik” [Quintessence Dental Technology] also by Quintessence Publishing (Berlin, Germany) he was serving as editorial board member (1997-2000), vice editor-in-chief (2004-2006) before being appointed as editor-in-chief (2007). In 2001 he was editorial chairman of the „Internationale Zahntechnik Magazin” [International Dental Technology Magazine] published by Flohr Publ. (Rottweil, Germany). He co-authored several book chapters, a textbook for dental students “Curriculum Prothetik” (1. ed. 1994 - 5. ed. 2021), a book on implant prosthodontics „Enossale orale Implantologie aus prosthetischer Sicht“ [Endosseous implantology from the prosthodontic point of view], published in 1996 by Quintessence Publishing and numerous journal articles. In recent past, he co-authored a book on dental CAD/CAM technology together with Prof. Dr. W. Att (Tufts University, Bosten, USA) and Prof. Dr. J.R. Strub (Emeritus, Freiburg) titled “Digital Workflow in Reconstructive Dentistry” published by Quintessence Publishing (2019). Siegbert Witkowski is a member of several national and international professional organizations.

June 2, 1968: Born in Kempten im Allgäu; 1990–1995: Studied dentistry at the Philipps University of Marburg; 1993: Accepted into the German National Academic Foundation; 1996: Doctoral studies at the University of Marburg; 1997: Assistant dentist in a dental practice near Cologne; 1998: Completed his doctorate on the subject of “Temperature development in dentine during dental preparation”; Since January 1998: Research assistant at the Clinic for Dental Prosthetics, Propaedeutics and Materials Science at the University Medical Center Schleswig-Holstein, Campus Kiel; April 2000: Appointment as senior physician; May 2001: Appointment as “Specialist for Prosthetics” by the German Society for Dental Prosthetics and Materials Science; 2006: Completion of the implantology curriculum (DGI); May 2006: Completion of habilitation (topic: “Evidence-based assessment of dental esthetics to improve quality of life”); Oct 2008: Appointment at the RWTH Aachen University to the W3 Professorship Clinic for Dental Prosthetics and Biomaterials, Center for Implantology; Since Oct 2008: Director of the Clinic for Dental Prosthetics and Biomaterials, Center for Implantology at the University Hospital Aachen; Since Nov 2008: Clinical focus for many years on dental implantology and implant prosthetics. In addition to implantology and implant prosthetics, Prof. Wolfarts’s research focuses on dental esthetics, the clinical testing of new all-ceramic materials, and the associated improvement in quality of life. He is a certified implantologist of the German Society of Oral Implantology (DGI) and an ITI Fellow (International Team for Implantology); Sep 2014: His book “Implant Prosthodontics – A patient-oriented concept” was published by Quintessence Publishing.