Ceramics, Labo OI (Mauritius), Permadental China Limited and SCDL Holdings, SCDL Finance Pty Ltd, SCDL Pty Ltd, Andent Pty Ltd, Proform Australia Pty Ltd, Dentmill Australia Pty Ltd, BU Factory Pty Ltd, Pavona Pty Ltd, Southern Cross Dental Laboratories (NZ) Limited and the Supervisor of MDLSZ and YZJSZ. From 1979 to 1981, he was a lecturer at The Hong Kong Polytechnic University (formerly known as The Hong Kong Polytechnic) and was primarily responsible for teaching dental technology. From 1981 to 1998, he was an instructor dental technologist at the Faculty of Dentistry, The University of Hong Kong and was primarily responsible for teaching dental technology. Mr. Ngai is the co-author of A Colour Atlas of Resin Bond Retained Prostheses A practical guide, a book published in 1989. Mr. Ngai obtained a Masters Degree in Management(Technology) from the University of Melbourne in Australia in December 1994 and a Bachelors Degree in Education from the University of Melbourne (Hawthorn Institute of Education) in Australia in May 1995. Mr. Ngai also obtained a Fellowship (dental) from The British Institute of Surgical Technologists (now known as The British Institute of Dental and Surgical Technologists) in the United Kingdom in May 1982, the dental technicians certificate from the City and Guilds of London Institute in the United Kingdom in June 1977, the dental technicians advanced certificate in orthodontic technology from the City and Guilds of London Institute in the United Kingdom in June 1980, the dental technicians advanced certificate in prosthodontic technology in June 1980, the dental technicians advanced certificate in crown and bridge technology from the City and Guilds of London Institute in the United Kingdom in June 1983 and the licentiateship of the City and Guilds for dental technology from the City and Guilds of London Institute in the United Kingdom in May 1990.  

 Orthodontics and Prosthodontics technology