A removable functional appliance or ‘Twin-Block’ functional appliance is used to treat problems of the bite, most commonly, where the bottom jaw is shorter than average, causing the top teeth to appear prominent. The removable functional appliance is worn in two pieces; one for the upper and one for the lower and they work together to improve how the upper and lower teeth bite together and correcting the appearance of prominent teeth. Because the Twin-Block is a brace that works best when a child is going through a growth spurt we advise any parent who is concerned about their child’s tooth development to have their child assessed before starting secondary school.