“…Human oral epithelial cells (HOECs) and periodontal ligament cells (PDLCs) were used in accordance with the ethical standards established in the Declaration of Helsinki. HOECs and PDLCs were stored, thawed and cultured as previously described [19][20][21]. HOECs were cultured in EpiGRO™ Human Epidermal Keratinocyte Complete Media Kit (Merck Millipore, Germany), and the medium for PDLCs and Cal 27 was α-MEM (Gibco, US) and DMEM (Gibco, US), respectively, and 10% (v/v) was supplemented with fetal bovine serum (FBS, Gibco, USA).…”