Week 5 - Cementum Flashcards
What is cementum made of?
Nearly 50/50 organic/inorganic split
What are the organic components of cementum?
- Type I collagen (intrinsic and Sharpey’s fibers)
- Proteoglycans
- Glycosaminoglycans
- Phosphoproteins
What does cementum provide an attachment for?
The PDL through sharpey’s fibers
How does cementum provide compensation for occlusal wear?
Through continuous apical apposition
- as the tooth wears down, reparative dentin lays down to stabilize
What may cementum participate in?
Repair of root fracture
What is the origin of cementum?
Ectomesenchymal
What is the quantity of mineral comparison of cementum, bone and dentin?
Cementum contains less mineral than both bone and dentin
Is cementum vascular?
Avascular, not innervated, and contains no haversion or volkmann’s canals
Where is cementum the thinnest?
At the CEJ (30-50 µm)
and progressively increases in thickness to 90-150 µm at mid-root to 150-300 µm at the apex
What are cementoblasts responsible for?
secretion of the organic matrix of cementum
What are cementoblasts derived from?
undifferentiate mesenchymal cells that originate in the proximal (inner) zone of the dental follicle
What are all cells in the dental follicle derived from?
Ectomesenchyme (neural crest cells)
How is differentiation initiated with?
disruption of Hertwig’s
epithelial root sheath, allowing the undifferentiated mesenchymal cells to make contact with the adjacent dentin
What induces differentiation process?
Dentin matrix growth factors (BMP, FGF, DMP)
What does hertwig’s root sheath contain for the mesenchymal cells to enter?
Perforations that make contact with growth factors and come from pulp through holes
What are histological features of cementum?
- Depositional lines
- Reversal lines
- Cementoblasts
- Cementocytes
- Lacunae
- Canaliculi
- Sharpey’s fibers (PDL)
What do depositional and reversal lines indicate?
Incremental growth, and run longitudinally within the cementum
What are the types of cementocytes?
Lacunae and canaliculi
What are lacunae?
Space occupied by cell
What are canaliculi?
Space occupied by cytoplasmic projections
- fingerlike projections; may help with intercellular communications
What are insertion points that suspend the tooth in space?
Sharpey’s fibers
What are the different ways cementum can meet enamel at the CEJ?
Overlap
End to end
Gap
What is abfraction?
Loss of tooth surface at the cervical areas of teeth
What is abfraction caused by?
Tensile and compressive forces during tooth flexure
What does abfraction affect?
Buccal/labial cervical areas of teeth
What does abfraction look like?
Deep, narrow V=shaped notch
What teeth does abfraction affect?
Single teeth with excursive interferences or eccentric occlusal loads
What is abrasion?
Loss by wear of dental tissue caused by abrasion
by foreign substance (e.g. toothbrush)
Where is abrasion usually located?
at cervical areas of teeth
What do abrasion lesions look like?
More wide than deep
What teeth are commonly affected with abrasion?
Premolars and cuspids
What are cementicles?
Calcified bodies appearing on or in the cementum
and in the PDL
What are cementicles classified as?
free, attached or embedded
What are cementicles a response to?
local trauma or hyperactive
occlusion and appear in increasing numbers with increasing age
What are cemental spurs?
Projections of cementum (trauma response)
What does exposed cementum prevent and why?
It is hypermineralized which
prevents reattachment of
collagen
- not as poreous so collagen and sharpey’s fibers have trouble reattaching
What does exposed cementum facilitate attachment of?
Plaque and calculus
What absorption does exposed cementumf acilitate?
Endotoxin absorption into cementum
What is this?
Calculus attachment to cementum
How does scaling and root planing benefit cementum?
Removes biofilm and cementum deposits
What is hypercementosis?
The excessive production of cellular cementum that generally involves the apical 1/3 of the root
What is the etiology of hypercementosis?
variable involving such factors as trauma from
occlusion, periapical inflammation, or compensation for occlusal
attrition
What are accessory canals beneficial for?
Vasculature to reach tissues which helps if there is a crack in the tooth so cementocytes can move via accessory canals
Where are accessory canals located?
More in the apex of the tooth (apical fracture has more help with healing)
- in multirooted teeth, the canal is in furications
