Root and Periodontium Flashcards
What makes up the periodontium?
cementum, alveolar bone, PDL, gingiva (tooth associated and gingival ligaments)
What defines the edge of the enamel organ during the bell stage?
cervical loop: a crown structure
What defines the forming root?
HERS: bilayer of inner and outer epithelium
What is HERS derived from?
cervical loop, extension of enamel organ, transforms from cervical loop
What is the function of HERS?
defines size and shape, and number of roots (canals) - morphogenesis
induces root odontoblast differentiation
How do get multiple roots?
epithelial growth - epithelial interradicular processes = tongues of epithelium growing toward one another to form canals
What becomes of HERS?
disintegrates shortly after inducing root odontoblast differentiation, some cells become epithelial rests of malassez
What are ERM?
remnant of HERS; appear as clumps in PDL surrounded by basement membrane, can be close or far from root
What is function of ERM?
can cause cysts, speculated to be involved in perio homeostasis or regeneration - not proven
What is the process of cell differentiation for root dentin?
ectomesenchyme -> dental papilla -> pre-odontoblasts -> odontoblasts
What are the types of dentin?
mantle, circumpulpal, predentin, primary/2˚/3˚ etc
What defines the types of cementum?
presence/absence of cells within its matrix and origin of major collagen fibers of matrix
What are the major types of cementum?
acellular = acellular extrinsic fiber cementum = 1˚; covers 2/3 root cellular = cellular intrinsic fiber cementum = 2˚; covers apical 1/3 root
what cells make up CIFC?
mix of acellular and cellular layers
Which type of cementum is formed first?
acellular
Special functions of cementum?
attachment = impt for strong periodontal structure; cement tooth in socket (Acellular primarily) protecting = root from resorption and repairing resorption pits adjusting = tooth position (cellular only) sealing = dentin tubules - hydrodynamic theory of dental sensitivity, inhibiting bacterial invasion
cementum composition
similar to bone, dentin
- 50% inorganic: mineral HA
- 35% organic: collagen type I, non-collagenous proteins and glycosaminoglycans (10%)
- 15% water
physiology of cementum
avascular, non-innervated, no turnover (growth by apposition)
Most to least frequently observed CEJ relationships
overlap > mett > gap
varies by tooth and location
What cells come from dental follicle?
cementoblasts, PDL fibroblasts, osteoblasts
before cementum can form
root dentin must be formed and HERS disintegrates exposing root dentin surface
what is the major fiber group for acellular cementum?
extrinsic fibers, critical to function of acellular cementum
What are sharpey’s fibers?
mineralized collagen fiber bundles providing strong anchorage of tooth-PDL-bone
What does the fiber fringe form when engulfed and mineralized?
Sharpey’s fibers
