 The epithelial components of the stem cells for continuously growing teeth form from tissue layers called the stellate reticulum and the suprabasal layer of the surface ectoderm.Ectodermal dysplasia is a rare but severe condition where the tissue groups (specifically teeth, skin, hair, nails and sweat glands) derived from the ectoderm undergo abnormal development.Ectodermal dysplasia is a vague term, as there are over 170 subtypes of ectodermal dysplasia.