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
