sentence: Currently , a total of six different dental stem cells ( DSCs ) including dental pulp stem cells ( DPSCs ) , stem cells from exfoliated deciduous teeth ( SHEDs ) , periodontal ligament stem cells ( PDLSCs ) , dental follicle progenitor cells ( DFPCs ) , stem cells from apical papilla ( SCAPs ) and gingival mesenchymal stem cells ( GMSCs ) have been isolated and identified ( Zhang et al ., 2009 ; Sedgley and Botero 2012 ) ( Figure 1A ) .