sulcular epithelium sulcular epithelium the sulcular epithelium is that epithelium which lines the gingival sulcus. it is apically bounded by the junctional epithelium and meets the epithelium of the oral cavity at the height of the free gingival margin. the sulcular epithelium is nonkeratinized. the gingival sulcus (g) is bounded by the enamel (a) of the crown of the tooth and the sulcular epithelium. the sulcular epithelium is that epithelium which exists on the sulcular side of the free gingival margin (f). the oral epithelium (e) exists on the other side of the free gingival margin.