Dr. Fillion is the first orthodontist in the world to practice exclusively lingual orthodontics and is considered one of the pioneers of lingual orthodontics;​

​ - Founder and Honorary Member of the French Society of Lingual Orthodontics (SFOL), he was the 1st President of the World Society of Lingual Orthodontics (WSLO 2004-2006). ​

- He was in charge of teaching lingual orthodontics at the University René Descartes Paris-V from 1996 to 2011, and is co-director of the Fellowship of Lingual Orthodontics at the University of Texas-San Antonio (USA).​

- He has shared his experience in 36 countries through lectures and courses, mainly in Japan, USA and Europe.​

- After having practised regularly as a clinician in Paris, London and Geneva, his private practice is now exclusively in Paris and always limited to lingual orthodontics for adults and teenagers.​