Guided tissue regeneration (GTR) has been widely used for periodontium regeneration for decades. It is a regenerative surgical technique that involves the procedure of raising mucogingival flap around affected teeth, scaling and planing root surfaces and placing barrier membranes temporally under gingiva. The purpose of this book is to understand the theoretical perspectives and the practical use of the GTR technique for the treatment of periodontal lesions, including furcations of more complex lesions, apical lesions, and large bone loss.