Abstract: It is possible to regenerate a tooth with new paradigm based on tissue engineering and regenerative medicine. However, a regenerative tooth can not survive in vivo or be applied in clinic, since periodontal diseases widely decrease the potential of regenerative teeth. Up to date, the treatment for periodontal diseases in clinic could not recover the regeneration capacity of periodontium successfully, probably because the function ofthe key cellsperiodontal ligament stem cells (PDLSCs) are not fully understood. The PDLSCs are similar as bone marrowderived mesenchymal stem cells (BMMSCs), but more easily attracted by inflammation. Therefore, how to protect the cells against the inflammatory cytokines become a key problem for periodontal regeneration. On one hand, tissue engineering and cell aggregate system can realize the periodontium regeneration under inflammatory microenvironment successfully. On the other hand, BMMSCs canbe recruited into defect part of periodontium and take part in the regeneration process. Therefore, both endogenous and exogenous therapies for periodontium are important for not only clinical treatment but also scientific research.

Key words: periodontal tissue, regeneration, mesenchymal stem cells, inflammatory microenvironment