Hygiene Atlas

Atlas · Plate III · Histology and Embryology · 05

Cementum, PDL and alveolar bone

Cementum is the softest of the tooth's hard tissues, about 45-50% mineral, with no blood or nerve supply; acellular cementum covers the cervical root and cellular cementum the apical third. PDL collagen fibers, anchored as Sharpey fibers, hold the tooth in bone, and the oblique group, the largest, resists biting force. The lamina dura is the socket lining seen on radiographs.

High-yield facts · 9

  1. Cementum is about 45-50% inorganic; it is avascular and has no innervation.S40
  2. Acellular (primary) cementum covers the cervical root; cellular (secondary) cementum is on the apical third and furcations.S40
  3. Sharpey fibers are PDL collagen fibers embedded in cementum and alveolar bone.S40
  4. The PDL is about 0.15-0.38 mm wide and thinnest at the middle third of the root.S40
  5. PDL principal fiber groups: alveolar crest, horizontal, oblique (most numerous), apical and interradicular (multirooted teeth only).S40
  6. Gingival fiber groups (e.g., circular, dentogingival, transseptal) support the gingiva; transseptal fibers connect adjacent teeth and contribute to orthodontic relapse.S40
  7. The lamina dura is the radiopaque radiographic image of the alveolar bone proper (cribriform plate).T7
  8. Normal alveolar crest sits about 1.5-2 mm apical to the CEJ.T7
  9. Cementicles are calcified bodies in the PDL.S40

Facts are written in our own words; each tag links to its source. Values marked "sources vary" differ between references, so check the one your program uses.