Dr. William J. Clark is a Scottish orthodontist known for developing Twin Block Appliance in Orthodontics.
He published a textbook in 2002 called Twin Block Functional Therapy - Applications in Dentofacial Orthopaedics.
[3] Dr. Clark is credited to be the first person part of a teleconference at a dental course in Chicago in 1990 which was eventually transmitted to 25 different cities via satellite.
Twin-block appliances are used to correct Class II malocclusions with a deficient mandible.
Clark recommended the appliance to be worn for at least one year in order to see any growth changes happening.