Intermediate Plexus PDL — MFDS Part 1 MCQ

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HardPhysiologyIntermediate Plexus PDLMFDS Part 1

In classical histological descriptions of the periodontal ligament, which feature was termed the intermediate plexus?

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Correct answer: C — Interdigitation of collagen fibre bundles associated with the cemental and alveolar bone sides

The correct answer is C. In classical descriptions, the intermediate plexus denotes a central region in which periodontal collagen fibre bundles associated with the cemental and alveolar bone sides interdigitate. It was historically proposed to facilitate adaptation during eruption and tooth movement. However, this functional interpretation should not be stated as established fact: experimental work found collagen turnover throughout the full thickness of the ligament rather than within a discrete metabolically active plexus. Vascular anastomoses occur in the PDL but do not define this term. PDL nerve fibres contain sensory endings rather than a central synaptic relay. Epithelial rests of Malassez are distributed remnants of Hertwig's epithelial root sheath, and osteoclasts occur at sites of alveolar bone resorption rather than forming the intermediate plexus.

Reference: Zwarych PD, Quigley MB. The intermediate plexus of the periodontal ligament: history and further observations. Journal of Dental Research. 1965;44:383–391. https://pubmed.ncbi.nlm.nih.gov/14278196/