## 1 Introduction  
The health of oral and periodontal tissue significantly affects the quality of life [1]. With the increase of human lifespan, the dental approaches to prevent inflammatory disease on the periodontium are increasing. The periodontium is composed of gingiva, periodontal ligament (PDL), alveolar bone, and cementum [2]. The action of the periodontium depends upon its structural integrity and interactions among its components. However, when periodontal disease occurs, the periodontium progressively gets destroyed, and this may lead to tooth loss [3].  
Periodontal treatment aims to reduce the inflammation tissues caused by bacterial plaque, to correct defects due to the periodontal disease, and to, in the end to regenerate new periodontal tissue [4; 5]. The ideal goal of periodontal regeneration is to obtain new cementum with PDL fibers connected to alveolar bone [5; 6]. Various surgical approaches including guided tissue regeneration (GTR) and guided bone regeneration (GBR) were introduced to regenerate tissues [5; 6; 7]. Those two concepts are defined in the Glossary of Periodontal Terms 4 th Edition as follows: \"Procedures attempting to regenerate lost periodontal structures through differential tissue responses. Guided bone regeneration typically refers to ridge augmentation or regenerative bone procedures; GTR typically refers to the regeneration of periodontal attachment. Barrier techniques, using materials such as expanded polytetrafluoroethylene (e-PTFE), polyglactin, polylactic acid, calcium sulfate, and collagen, are employed in the hope of excluding epithelium and the gingival cerium from the root or existing bone surface in the belief that they interfere with regeneration\" [8]. Conventional GTR is theoretically based on the different growth speed of gingival fibroblast and the mesenchymal cells in PDL [9]. Use of a barrier membrane is a procedure for epithelial exclusion in order to promote the healing of periodontal tissues in such a way that the original structure and function is preserved instead of repairing with junctional epithelium [9]. During the occlusive period, the cells including cementoblast, osteoblast, osteoclast, and mesenchymal cells from PDL are activated to rebuild their missing tissues [5; 6; 7; 8; 9].  
For successful regeneration, both GTR and GBR procedures are used to achieve stability of blood clot, wound site healing, and isolation of the bone healing site from soft tissues, and to provide adequate space for bone healing [10]. The \"PASS principle\" suggests four biological principles necessary for the bone regeneration, which are (1) primary wound closure to ensure uninterrupted healing; (2) angiogenesis to provide blood and nutrient supply, as well as delivery of pro-healing cell types; (3) space maintenance for new bone growth while preventing soft tissue in-growth; and (4) stability of wound to include blood clot formation [11]. Furthermore, an additional five principles from a surgeon's perspective are suggested as (1) the appropriate and adequate membrane must be chosen; (2) promotion of healing of primary soft tissues; (3) primary closure of the membrane when possible; (4) stabilization of the membrane at the adjacent bone; (5) sufficient long-term healing [12]. There are many advances in regeneration therapy in periodontal tissues, but only the developments of membranes and grafting materials are reviewed in this article.