Hertwig Root Sheath — MFDS Part 1 MCQ

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ModerateAnatomy (Head & Neck)Hertwig Root SheathMFDS Part 1

During root development, the pattern of apical growth and folding of Hertwig's epithelial root sheath most directly determines which feature of the mature tooth?

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Correct answer: D — Root shape and number of roots

Explanation lettering: D = shown as A · C = shown as B · E = shown as C · A = shown as D · B = shown as E

A is correct. Hertwig's epithelial root sheath (HERS) forms when the inner and outer enamel epithelia meet at the cervical loop and proliferate apically after crown formation. Its growth outlines the developing root, while inward extensions and fusion in the furcation region partition multirooted teeth; it therefore contributes to root shape, length and number. Crown form and cusp pattern are established earlier during enamel-organ morphogenesis. Enamel thickness is determined principally by ameloblast activity. Dentinal tubule dimensions reflect odontoblast arrangement and dentine deposition rather than HERS morphology. HERS participates in signalling during radicular dentin and cementum development, but cementum thickness is not the principal morphological feature determined by its growth pattern.

Reference: Xiong J, Gronthos S, Bartold PM. Role of the epithelial cell rests of Malassez in the development, maintenance and regeneration of periodontal ligament tissues. Periodontology 2000. 2013;63(1):217-233. https://pubmed.ncbi.nlm.nih.gov/23931062/