W9 Cementum

Question 1

What is the periodontium?

Answer 1

Collecgively refers to cementum, alveolar bone and periodontal ligament

Question 2

What is cementum?

Answer 2

Avascular, receives nutrition from PDL space

Question 3

What is the function of cementum?

Answer 3

Covers the root surface, seal for the dentinal tubes. Provide attachment for the PFL fibers hold the tooth in it’s socket

Question 4

What is the chemical properties of cementum

Answer 4

Inorganic: 45-50% calcium hydroxyapatite
Organic matrix: Collagen fibers, ground substance
Bound water

Question 5

What are the physical properties of Cementum?

Answer 5

Yellow, lighter than dentine. Less mineralised than dentine and enamel, hard as bone. Lack lusture, softer than enamel

Question 6

What is the histology classification of cementum?

Answer 6

1. Acellular or Cellular cementum?
2. Nature of Organic matrix fibers - extrinsic or intrinsic
3. Combination of 1 and 2

Question 7

Describe acellular cementum?

Answer 7

Layer immediately overlying dentine. Deposited by epithelial root cells before root sheet disintergrates. Provides attachment

Question 8

Describe Cellular cementum

Answer 8

Thicker layer of cellular cementum. Deposited by cementoblasts, has an adaptive role in response to tooth wear/movement - faster formation. Has Cementocytes

Question 9

What are extrinsic fibres?

Answer 9

Sharpeys fibers are a portion of the collagen fibers from the PDL inserted at90 degrees on the outer part of the cementum

Question 10

What are intrinsic fibers

Answer 10

Derived from cementoblasts and lay parrallel to root surface at approx right angels to extrinisc fibres

Question 11

What is cemental caries?

Answer 11

Root caries that travels into cementum due to gingival recession due to trauma or periodontal disease

Question 12

What is concresence?

Answer 12

Union of root structure of more than one two by the cementum

Question 13

What is PDL?

Answer 13

Fibrous connective tissue between alveolar process and cementum. Composed of CT, fibers, cells and ground substance

Question 14

What is the function of PDL?

Answer 14

Provided attachment of the teeth to the surround alveolar bone by cementum. TO withstand mastication forces.

Question 15

What is the histology composition of PSL?

Answer 15

CT fibers: sharpeys fibers

Ground substance 70% water with glycoproteins and proteoglycans, nerves, highly vascular

Question 16

What cells are present in to PDL composition?

Answer 16

Fibroblasts: form fibers
Osteoblasts: bone formation
Cementoblasts: form cementum
Endothelial cells
Macrophages and osteoclasts
Epithelial rests 
Undifferentiated mesychymal cells

Question 17

What is the PDL Organisation?

Answer 17

Gingival Group - located around necks of the teeth
Transeptal - cementum to cementum
Dentoalveolar - cementum to bone

Question 18

What is the Gingival FIbre group

Answer 18

1. Alveologingival (free)
2. Dentogingival (attached)
3. Circumferential fibres
4. Dento periosteal ligament

Question 19

What is the Transsetal Group?

Answer 19

Inserts interproximally from cervial cementum of one tooth to the cervical cementum of neighbouring teeth. Withstands rotational forces

Question 20

What is the Dentoalveolar group?

Answer 20

1. Alveolar crest group - resist tiliting
2. Horizontal group - mesial, distal buccal lingual tilting + rotational
3. Oblique group:
4. Apical group: extrusive + rotational forces
5. Interradicular

Question 21

What is the chemical composition of alveolar bone?

Answer 21

60% inorganic - hydroxy
25% organic
15% water

Question 22

What is the gross anatomy of the alveolar bone?

Answer 22

Cortical plate, cribriform plate, cancelous bone