Guided Tissue Regeneration, PeriodontalGuided Tissue RegenerationAbsorbable ImplantsGingival DiseasesAlveolar Bone LossBone RegenerationMembranes, ArtificialGingival RecessionBone SubstitutesRegenerationNerve RegenerationLiver RegenerationTissue EngineeringTissue ScaffoldsBiocompatible MaterialsWound HealingRegenerative MedicineAnimal FinsStem CellsPeriodontal LigamentMesenchymal Stromal Cells