Cementum histology Flashcards
What is cementum more similar to; bone or teeth?
Cementum is more similar to the bone than to the teeth Because of embryonic origin
Amount of organic/inorganic content
Histological origin
What is cementum?
Hard avascular connective tissue that covers the teeth.
What does cementum do?
It protects and covers the root dentin
It provides attachment of periodontal fibers (Slightly mobile attachment)
It reverses tooth resorption (Due to loss of vascularization)
Where is cementum thickest?
Varies in thickness; thickest at apex and inter radicular areas of multirooted teeth but thinnest in cervical area
10 - 15 micrometers in the cervical areas and 50 to 200 micrometers apically
How is cementum different to bone?
Not vascularized (resistant to resorption)
Minor ability to remodel
More resistant to resorption compared to bone
Lacks neural component
70% of bone is made up by inorganic salts whereas cementum only has 45 - 50%
2 unique cementum molecules: Cementum attachment Protein and IGF
What happens if too much force is applied to teeth?
If too much force is applied the tooth will be resorbed
How does cementum develop?
Cementum formation occurs along the entire root sheath
HERS extension of the inner and outer epithelium
HERS becomes interrupted
Ectomesenchymal cells from the inner part of the dental follicle come in with predentin by differentiating cementoblasts
Cementoblasts lay down cementum
What proteins are essential for cementogenesis?
Growth factors:
TGF
PDGF
FGF
Adhesion molecules (In ECM):
Bone sialoprotein
Osteopontin
What is the function of the growth factors in cementogenesis?
Help induction of cementoblasts and positioning)
What are the physical properties of cementum?
Pale yellow witha dull surface
Cementum is more permeable than other dental tissues
Relative softness and the thinness at the cervical portion means that cementum is readily removed by the abrasion then gingival recession exposes the root surface
to the oral environment
What are the layers of cementum?
Acellular cementum
Cellular cementum
Hyaline layer (of Hopewell Smith)
Granular layer of tomes
How is cementum classified?
Presence or absence of cells
Origin of collagenous fibers of the matrix
Prefunctional and functional
What is the chemical composition of cementum?
Similar to bone
45 to 50% hydroxyapatite (inorganic)
50 to 55% collagenous (mostly type 1 collagen) and noncollagenous matrix proteins
What are the theories regarding how cementoblasts get activated to lay down cementum?
3 theories:
- Infiltrating dental follicle cells receive reciprocal
signal from the dentin or the surrounding HERS cells
and differentiate into cementoblasts - HERS cells directly differentiate into
cementoblasts - What are the function of epithelial cell rests of
Malassez? (perhaps they’re related)
How does the apex become narrow?
Continuous deposition of cementum at apex leads to its narrowing.
This occurs in the cellular part of the cementum
This can wither away creating an avenue for passage of material from pulp to gingiva
Where are cellular and acellular cementum located? What is the purpose of cells in cellular cementum?
Acellular cementum: covers the root adjacent to dentin whereas cellular cementum is found in the apical area
Cellular: Apical area and overlying acellular cementum. Also common in interradicular areas.
Cementum is more cellular as the thickness increases in order to maintain viability. The thin cervical layer requires no cells to maintain viability as the fluids bathe its surface
What are the contents of the cementoid?
It is a young matrix that becomes secondarily mineralized
How is cementum deposited?
Cementum is deposited in increments similar to bone and dentin
Are acellular and cellular cementum formed from two different sources?
One theory is that the structural differences between
acellular and cellular cementum is related to the faster rate of matrix formation for cellular cementum.
Cementoblasts get incorporated and embedded in the
tissue as cementocytes.
Different rates of cementum formation also reflected in more widely spaced incremental lines in cellular cementum
Where is the CE junction located?
On the cervical line msotly:
60% of cementum overlaps enamel
30% of cementum just meets enamel
10% of cementum forms a small gap between cementum and enamel
What happens to cementum with aging?
- Smooth surface becomes irregular due to calcification of ligament fiber bundles where they are attached to cementum
- Continuous deposition of cementum occurs with age in the apical area. [Good: maintains tooth length; bad:
obstructs the foramen] - Cementum resorption:
Active for a period of time and then stops for cementum deposition creating reversal lines - Resorption of root dentin occurs with aging which is covered by cemental repair
What are cementicles?
Calcified ovoid or round
Nodule found in the PDL
Single or multiple near the
cemental surface
Free in ligament; attached or embedded in cementum
Aging and at sites of trauma
What is the origin of cementicles?
Nidus of epithelial cells that are composed of calcium phosphate and collagen to the same amount as cementum (45% to 50% inorganic and 50% to 55% organic)
What is cemental repair?
Protective function of cementoblasts after resorption of root dentin or cementum.
Resorption is usually due to trauma.
Loss of cementum is accompanied by loss of attachment
Following reparative cementum deposition attachment is restored
What clinical application is there to understanding the cementum?
Cellular cementum is similar to bone but has no nerves. Therefore, it is non - sensitive to pain. Scaling
produces no pain, but if cementum is removed, dentin is exposed causes sensitivity
What are the features of hypercementosis?
Hypertrophy
Hyperplasia
Excementosis
Cementicles
What results if there is a root fracture?
A cemental callus forms
