In dentistry, the epithelial cell rests of Malassez (ERM) or epithelial rests of Malassez (''pax epithelialis pediodontii'') are part of the

periodontal ligament The periodontal ligament, commonly abbreviated as the PDL, are a group of specialized connective tissue fibers that essentially attach a tooth to the alveolar bone within which they sit. It inserts into root cementum on one side and onto alveo ...

cells around a

tooth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tea ...

. They are discrete clusters of residual cells from Hertwig's epithelial root sheath (HERS) that didn't completely disappear. It is considered that these cell rests proliferate to form epithelial lining of various odontogenic cysts such as radicular cyst under the influence of various stimuli. They are named after

Louis-Charles Malassez Louis-Charles Malassez (21 September 1842 – 22 December 1909) was a French anatomist and histologist born in Nevers, department of Nièvre. He studied medicine in Paris, where he worked as an ''interne'' from 1867. He served with the 5th Ambu ...

(1842–1909) who described them. Some rests become calcified in the periodontal ligament ( cementicles). ERM plays a role in cementum repair and regeneration. The stem cells in ERM can undergo an

epithelial Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...

–

mesenchymal Mesenchyme () is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood, or bone. The interactions between mesenchyme and epithelium help to form nearly ever ...

transition and differentiate into diverse types of cells of

mesodermal The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical Embr ...

and

ectodermal The ectoderm is one of the three primary germ layers formed in early embryonic development. It is the outermost layer, and is superficial to the mesoderm (the middle layer) and endoderm (the innermost layer). It emerges and originates from the o ...

origin like bone, fat, cartilage and neuron-like cells.

References

Further reading