Fibril diameters in the extracellular matrix of the periodontal connective tissues of the rat.
Level 5 - mechanism / opinion, no new human data
Animal ultrastructural laboratory study (non-human model)
PubMed 6453691 · doi:10.3109/03008208109152132
What was done
Electron microscopy was used to measure collagen fibril diameters across three periodontal connective tissues in the rat mandible: incisor periodontal ligament, incisor enamel-related connective tissue, and molar periodontal ligament. Investigators also evaluated fibril diameter variation between animals and within individual fiber bundles, tested whether fibril diameters followed claimed multiples of 8 nm, and assessed ground substance proportion and oxytalan fiber presence.
What was found
Collagen fibril diameters across all three distinct periodontal tissues showed a similar distribution, averaging 45 nm. Diameters varied across individual animals, between adjacent fiber bundles, and within single bundles. No evidence was found supporting previous claims that collagen fibril diameters occur in multiples of 8 nm. Extracellular matrix ground substance accounted for an estimated 65% of periodontal collagen fiber bundles or sheets. Despite previous light microscopy reports describing abundant oxytalan fibers, only a single fiber with oxytalan characteristics was identified via electron microscopy.
Why it matters
This study provides baseline ultrastructural morphology of rodent periodontal collagen architecture, showing uniformity in average fibril size (45 nm) across functionally diverse tissues and challenging prior theories regarding quantized 8-nm fibril increments and abundant oxytalan content.
Limits
The abstract does not report the total number of rats or micrographs evaluated. The study is descriptive, conducted exclusively in a rat mandibular model, and may not generalize to human periodontal biology. Functional interpretations were discussed but not experimentally tested.
Cited by
- supports Periodontal ligament fibers are hundredths the width of a human hair.