A Twin Block is a functional appliance used in growing children to modify the growth of the upper and lower jaws. The appliance is made of two separate removable plates, one worn on the upper jaw and the other worn on the lower jaw. Worn together, the Twin Block protrudes the lower jaw into a more harmonious relationship with the upper jaw and when worn for an extended period of time, this postural change becomes permanent. The Twin Block can also be used to expand the upper jaw.
A Twin Block is recommended in growing children with developing overbite problems that are caused by deficient growth of the lower jaw, seen clinically as a retruded lower jaw or chin.
In most developing overbite problems a constriction or narrowing of the upper jaw also occurs and expansion of the upper jaw is required in combination with forward movement of the lower jaw.
A Twin Block is only successful in growing children and is best used at the time of the adolescent growth spurt. This is usually around 10 to 12 years of age in girls and 11 to 13 years in boys. However, this varies from one child to another and we may recommend the use of a Twin Block appliance earlier than this if there is significant risk of trauma to protruding upper front teeth or if dental development and growth dictates earlier or later use of the appliance.