 Welcome to Peridontology Lecture Series. Every dental student is familiar with the term GTR that is guided tissue regeneration. In this short lecture class, we will discuss in a very simplified pictorial way about this concept. We will have a quick recap on Peridontology. It includes the investing gingiva and supporting alveolar bone, peridontal ligament and cementum. Whenever bacterial insults occur, changes happen in the gingiva and peridontium. The initial gingivitis can be reverted easily with proper treatment, but when it progress to peridontitis with attachment loss and bone loss, the treatment and healing becomes little complicated. If we are providing adequate treatment including non-surgical and surgical therapies, the tissues start to heal. The region can be repopulated by different types of cells. The arrow A indicates the cells, that is the epithelial cells, B is the connected tissue cells of gingiva, C are the alveolar bone cells and D the cells from peridontal ligament. We can imagine a car race, so whoever wins the race repopulates the area and determines the fate of healing. If the epithelial cells repopulate, then it forms the long-junctioned epithelium. If the connected tissue cells of gingiva comes, then connected tissue adhesion with parallel fibers form. If bone cells repopulate, then root resorption and ankylosis occur. These all result in compromised repair. In the diagram, the first three pictures depicts repair, which is not desirable because it is prone for recurrence of the disease. Ideally, what we want is regeneration of lost alveolar bone, peridontal ligament and cementum, which can occur only if peridontal ligament cells repopulate. This regeneration is the most desirable outcome, so we need to do something. That is, we need to exclude the undesirable cells by creating a barrier. This picture of aircraft might help you to memorize it. We need to exclude the cells which we don't want to repopulate and make the region favorable for the repopulation of peridontal ligament cells, which forms the basis of Melcher's concept. In the diagram, imagine red cells as epithelial and connected tissue cells from gingiva, which we don't want to interfere in healing, and blue, considered as peridontal ligament cells, which help in attaining proper regeneration. Now, coming to the clinical scenario, in the surgery after depriving the area and removing granulation tissues, bone grafts may be used and root biomodification may be done. And over that, barriers, that is membranes, can be used to exclude the undesirable cells. There are different types of membranes and different generations of membranes. Non-dissorbable membranes like millipores, Teflon were first used, but they needed a second surgery to remove it at a later time, that is around three to six weeks. And they are non-dissorbable. Then, resorbable membrane scheme, like OxyQuest, Bioguide, At-Dissorb, they were used. Now, resorbable membranes with growth factors are also available. GTR is more predictable in vertical defects. Class 2 vocation involvement in teeth with less gingival recession, teeth having wide keratinase gingiva, thick gingiva, and in those teeth with wild interdental space. It is most favourable in teeth with minimum mobility and in those persons with good oral hygiene. Few measurements we need to keep in mind. While placing membranes, that is, the apical border of membrane should be 3 to 4 mm apical to the defect, laterally 2 to 3 mm beyond the defect. One more measurement, that is, it should be placed 2 mm apical to the cementary enamel junction of the teeth. Membrane exposure should be avoided and stability should be maintained with proper suturing techniques. If conditions are favourable, adequate regeneration of lost attachment apparatus occurs. And as weeks and months pass by, the resorbable membranes resorb by itself according to the type used. As you can see in the picture, the membrane dissolves by itself if it is a resorbable membrane. This is the case from a standard textbook which explains the whole process. A deep vertical defect is diagnosed clinically and radiographically. After surgical exposure and debridement, membranes work place and sutures. Sutured, in the re-entry, surgical stage, excellent regeneration can be appreciated clinically and radiographically. So to conclude, GTR, our guided tissue regeneration, is the method for the prevention of epithelial migration along the semen cell wall of the pocket and maintaining space for clot stabilization. Hope the concept of GTR is clear. Thank you.