The Twin Block Appliance is a removable device used to correct a Class II malocclusion in a growing child. It is made up of two acrylic bite blocks, one on the top and one on the bottom, hence the name “twin block.” When the child opens and closes their mouth, the two acrylic blocks work together encourage the child to move their lower jaw forward. The top part of the Twin Block may contain an expansion screw, which helps to expand the palate. There are several different types of Twin Block devices, used for various situations. The Twin Block was invented by Scottish orthodontist William Clark in 1977.
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