Regeneration is the reproduction or reconstitution of a lost or damaged tissue through the formation of a new one that can reproduce the form, structure and function of original tissues. Tissue regeneration is a complex process that needs a sequence of molecular events, such as cell adhesion, migration, multiplication and differentiation. Tissue engineering is an interdisciplinary science that applies the principles of engineering and biological sciences in order to develop biological substitutes for tissues and injured and/or lost organs. In the medical field, these techniques are already used and are widely established. However, they have been used most recently for concepts of tissue engineering in dentistry. The Guided Tissue Regeneration (GTR) is a technique used in dentistry that also aims at tissue and bone regeneration, or to repair damaged tissue. It is based on the perception that tissues, for the most part, are capable of self-reconstitution if appropriate conditions are provided. As explored in this book, the use of the GTR technique for the treatment of periodontal lesions, including furcations of more complex lesions, apical lesions, and large bone loss, is now a reality, as it is evidenced by the regeneration capacity of the periodontal tissues.