Cementum Flashcards
List the types of cementum discussed in your text.
Intermediate
True Cementum
Describe each type of cementum given the criteria in your texts.
Intermediate -from HERS cells (epithelial root sheath) -seal dentinal tubules True Cementum -bone like substance from cementoblasts
Associate each type of cementum with the tooth and with the periodontal space.
continuos with the PDL-adherent to the dentin
FINISH
What terms are used to define true cementum
(2)
- cellular
2. acellular
Compare cementum with the other types of mineralized tissues.
Cementum is mineralized periodontal support tissue-as is alveolar bone. Cementum is ~50% mineralized
Microscopic components of acellular cementum (2)
- no cementocytes - but still contain both fiber types
2. cementoid
The process of cementum formation - cementogenesis (3)
- begins at root formation
- continues throughout life
- can be a reparative process in root resorption
Intermediate Cementum
- Substance?
- Produced when?
- Location?
- Formed from?
- Thickness?
- Produced by?
- Mineralization compared to cementum, dentin, and enamel?
- Protein?
There is a mineralized substance produced during formation of the tooth root.
In the developed root, this substance is located between the granular layer of Tome’s and the true cementum.
When the microanatomy of the tooth had been first described, it was assumed (incorrectly) that the cells which form cementum also formed this substance.
Unfortunately, this substance is called intermediate cementum.
The layer of intermediate cementum is 10 nm in thickness and is formed by the same cells which produce enamel.
Intermediate cementum, like enamel, is more highly mineralized than either dentin or cementum.
Intermediate cementum, like enamel, contains the enamelin protein group.
How intermediate cementum is formed and its developmental relationship to the root of the tooth will be discussed fully during our consideration of tooth development.
Where is intermediate cementum found?
in the developed root it is located between the granular layer of Tome’s and the true cementum
How thick is the layer of intermediate cementum?
10nm in thickness
What two dental substances does intermediate cementum separate?
the granular layer of Tome’s and the true cementum
What dental tissue does intermediate cementum most closely resemble? How?
Closely resembles enamel in its mineralization, protein makeup (enamelin), and is even produced by ameloblasts
What terms are used to define true cementum
(2) and describe them
- cellular
- acellular
*Based on how fast they were formed
What are the microscopic components of cellular cementum?
4
- cells called cementoblasts produce and mineralize cementum
- cells surrounded by matrix called cementocytes whose processes are polarized toward the periodontal space.
- hydroxyapatite crystals
- an organic matrix called cementoid produced by cementoblasts consisting of ground substance and two types of collagen fibers
(a) collagenous fibers produced by cementoblasts and are called intrinsic fibers
(b) collagenous fibers of the periodontal ligament embedded in the matrix are called extrinsic fibers or Sharpey fibers; these are fibers which anchor the tooth in its socket
Cells which are surrounded by matrix and have processes which are polarized towards the PDL
Cementocytes
Where are cementocytes found on a histological slide?
near the PDL-Cementum
Cells which produce and mineralize cementum
Cementoblasts
The Cementoenamel Junction
-Four Different Arrangements
NUMBERS DO NOT MATTER!!
- Cementum overlaps enamel
a. (12% Arambawatta 2009, not mentioned in Chiego) - Cementum and enamel exactly meet
a. (30% Chiego vs 55% Arambawatta) - Cementum and enamel fail to meet Gap
a. (5-10% Chiego vs ~30% Arambawatta)
**KNOW: gap is responsible for dentin hypersensativity, for bleaching, and for osteoclast to get into bone
b. Potential for root caries / hypersensitivity / external root resorption?
- Enamel overlaps cementum
a. (~1-2% Arambawatta vs 60-65% Chiego)
Physical Characteristics of True Cementum
(3)
Mineralization? Vessels?
- About 50% mineralized (equal to or slightly less mineralized than bone)
- Avascular - making it difficult to heal
- Aneural - No Pain - making us unaware of inflammation
The Cementoenamel Junction
-Four Different Arrangements
NUMBERS DO NOT MATTER!!
- Cementum overlaps enamel
- Cementum and enamel exactly meet
- Cementum and enamel fail to meet Gap
**KNOW: gap is responsible for dentin hypersensativity, for bleaching, and for osteoclast to get into bone
- Enamel overlaps cementum
Physical Characteristics of True Cementum
(9)
Mineralization? Vessels (2)? Proteins? Color? Resistance to P? Lifespan Thickness (2)
- About 50% mineralized (equal to or slightly less mineralized than bone)
- Avascular - making it difficult to heal
- Aneural - No Pain - making us unaware of inflammation
- Important extracellular glycoproteins (fibronectin, tenascin, vitronectin and osteopontin
- Same color as dentin (This poses a problem for procedures such as root planing).
- Cementum is MORE resistant than bone to destruction by pressure (Important for orthodontists ).
- Cementum is produced throughout life and is effective in repairing horizontal root fractures, but not vertical root fractures
- The thickness of cementum varies. Thickness at the cementoenamel junction is about 10-60 microns and increases apically to 200 microns or more at the tip of the apex
- Cementum thickness increases with age and may occlude the accessory and apical foramina. Apical vasculature is constricted.
What is the significance of the gap between cementum and enamel
- Cementum and enamel fail to meet Gap
**KNOW: gap is responsible for dentin hypersensativity, for bleaching, and for osteoclast to get into bone (root caries)
Composition of cementioid
2 types of collagen
- intrinsic fibers
- Extrinsic fibers
Describe and define the 2 types of collagen which make-up the cementoid
intrinsic fibers-collagenous fibers produced by cementoblasts
extrinsic fibers OR Sharpey fibers-collagenous fibers of the PDL embedded in the matrix-Anchor the tooth in its socket
Produces intrinsic fibers
cementoblasts
Sharpeys fibers
Also known as extrinsic fibers collagenous fibers of the PDL embedded in the matrix-Anchor the tooth in its socket
When does cementum formation begin
At root formation
When does cementum formation end
goes through life
Can root resorption be repaired by the body?
Cementum formation can repair root resorption
Can root resorption be repaired by the body?
Cementum formation can repair root resorption
- Important extracellular proteins of cementum (4)
Glycoproteins (4)
fibronectin
tenascin
vitronectin
osteopontin
Color of cementum and clinical significance
Similar to dentin which is a problem for root planing
Cementum resistance to Pressure and compare to bone-Significance?
Cementum is MORE resistant than bone to destruction by pressure (Important for orthodontists ).
Cementum is produced throughout life and is effective in repairing what but not what
horizontal root fractures, but not vertical root fractures
Thickness of cementum
The thickness of cementum varies. Thickness at the cementoenamel junction is about 10-60 microns and increases apically to 200 microns or more at the tip of the apex
Cementum thickness increases with age and may occlude the accessory and apical foramina. Apical vasculature is constricted.
Cementum-Forming Cells
Cementoblasts
- Active
- Inactive
- osteoclast-like cells
Cementum-Forming Cells
Cementoblasts
- Active
- Inactive
- osteoclast-like cells
Cementum forms how? Makeup?
- A usual rule of thumb is that when cementum forms slowly, it is acellular.
- There is usually a thin layer of acellular cementum laid down as the root forms.
- When cementum forms more rapidly, cementoblasts are trapped in the matrix and become cementocytes.
- Distribution of more acellular cementum is seen near CEJ and more cellular cementum occurs at apex and in furcations.
As the root forms what is laid down?
a thin layer of acellular cementum
What happens when cementum forms more rapidly?
Cementoblasts are trapped in the matrix and become cementocytes
Distribution of more acellular cementum is seen near where? (2)
near the CEJ and more cellular cementum occurs at the apex and in furcations
Number of intrinsic fibers
few
Intrinsic fibers are produced by what? in what?
intrinsic fibers are produced by cementoblasts in secretion of cementoid
Orientation of intrinsic fibers
Parallel to the long axis of the tooth
Do acellular and cellular have intrinsic fibers?
Yes
Extrinsic fibers are more commonly known as
PDL fibers
What produces extrinsic fibers aka PDL fibers
NOT cementoblast, but fibroblast
what can be the result of hypercementosis (4)
- Abnormal O forces
- Cementoma
- Padget’s disease
- Cementicles (attached and free)
Apical migration of the gingiva leads to _______
Cementum exposure–> will lead to death of cementum since it receives nutrients from capillaries in adjacent CT
How does cementum receive its nourishment
by diffusion from the capillaries in adjacent CT
Exposed cementum may be what?
It is considered what?
May be hypo-mineralized
Considered dead
Dead, exposed cementum is coated with what
exotoxins and endotoxins in crevicular fluid
In order for what to happen, dead cementum must be removed
soft tissue healing or reattachment-Thus use SRP
Define cementicles
nodules of cementum produced by cementoblast
Three types of cementicles
Attached to root
unattached to root
Forming around epithelial remnants in the PDL
Clinical significance of cementicles (nodules of cementum)
(2)
3rd but not sure what it has to do with this??
Since cementum continues to grow throughout life these nodules may get large enough to cause root resorption of bone by exerting pressure on the bone lining the socket
May occlude the root foramen
Regenerating cementum may be a key to encouraging complete periodontal regeneration. Emdogain aims to accomplish this.
What does emdogain aim to accomplish
Regenerating cementum by encouraging Periodontal regeneration
Aging of Cementum
1. appearance and suceptibility
- Areas of resorption appear
- Occlusion of apical foramen
- Susceptible to cemental tears/fractures
Tooth wear in terms of cementum
Compensatory super-eruption due to cementum deposition at the apex
What happens due to cementum deposition at the apex?
Compensatory super-eruption