A collar of non-keratinized epithelial cells forming the biological attachment to the tooth surface at the base of the gingival crevice (sulcus) in the region of the cemento-enamel junction (CEJ). It is formed from the reduced enamel epithelium. It contains very small rivet-like structures in the cell wall (hemidesmosomes) which link the internal basement membrane of the junctional epithelium to the tooth surface. It consists of stratified squamous cells approximately 15–30 cells thick, coronally tapering to about 5 cells thickness apically. It plays an important role in periodontal health. The external basal lamina is a thin mat of extracellular matrix between the epithelial cells of the junctional epithelium and the gingival connective tissue. The internal basal lamina is a thin mat of extracellular matrix between the epithelial cells of the junctional epithelium and the tooth surface. The long junctional epithelium refers to the healing process in the dento-gingival junction following treatment of chronic periodontitis, especially root debridement. The junctional epithelium heals in the cleaned environment and forms a long band of epithelial cells attached to the tooth surface by a hemidesmosomal attachment.