Book excerpt: Twin Block appliances are simple bite blocks that are designed for full-time wear. They achieve rapid functional correction of malocclusion (misalignment of upper and lower teeth) by the transmission of favourable occlusal forces to occlusal inclined planes that cover the posterior teeth. The forces of occlusion are used as the functional mechanism to correct the malocclusion (www.twinblocks.com). Beginning with an introduction to orthodontics and twin blocks, the next chapters describe growth studies and diagnosis and treatment planning. Each of the following sections discusses the use of twin blocks for different types of malocclusion. With a focus on the latest developments in functional therapy, the book offers guidance on diagnosis, treatment planning, case selection, appliance design and clinical management. Written by the internationally recognised Orthodontist William Clark from Fife, UK, who also invented Twin Blocks, this comprehensive guide includes nearly 600 clinical photographs and illustrations. Key points Comprehensive guide to use of Twin Blocks in treatment of malocclusion Focus on latest developments in functional therapy Written by UK-based inventor of Twin Blocks Includes nearly 600 images and illustrations