W8 Peridontium, Cementum, Alveolar bone

Question 1

Define the periodontum

Answer 1

Collectively refers to the cementum, alveolar bone, and periodontal ligament

Question 2

Define Cementum

Answer 2

In health is not visible, no nerve supply, avascular, recieves nutrition from PDL space

Question 3

What is the function of the peridontium?

Answer 3

• Covers root surface
• Seal for dental tubules
• Attachment for the periodontal ligament fibers that hold tooth in socket

Question 4

What is the chemical matrix of cementun?

Answer 4

Inorganic: 40-50% calcium hydroxyapatite
Organic: 50-55% Collagen fibres
- Bound water

Question 5

What are the physical properties of cementum?

Answer 5

• Less mineralised than dentine & enamel
• Approximately as hard as bone
• Yellow slightly lighter than dentine
• Lacks lustre, in contrast to enamel
• Softer than enamel, low abrasion resistance
• Unusual, may characteristics of hard tissue, but some are absent

Question 6

How can cementum be classified?

Answer 6

1. Presence or Absence of Cells (acellular or cellular)
2. Nature of Organic Matrix fibers (extrinsic or intrinsic
3. Combination of 1 &2

Question 7

Define Acellular cementum

Answer 7

Layer immediately overlying the dentine, formed completely before the deposition of secondary cementum begins. Role is to provide attachment.
Deposited by the epithelial root cells,before root sheath cell disintegrated

Question 8

Define Cellular Cementun

Answer 8

Thick layer of Cellular cementum covers the apical part of the root
• Deposited by cementoblasts of the PDL
• Cementocytes
• No nerves, relatively avascular nutrition from PDL via cementocytes process
• Has a adaptive role in response to tooth wear/movement
• Faster rate of matrix formation

Question 9

Define cementocyte

Answer 9

cementum cells, located with in the cellular cementum

Question 10

Define odontoblasts

Answer 10

Form new cementum

Question 11

What are extrinsic fibers?

Answer 11

Sharpey fibers are a portion of the collagen fibers from the PDL, that are partially inserted into the outer part of the cementum at 90deg to the cemental surface.

Question 12

Define Intrinsic Fibers

Answer 12

Derived from cementoblasts, parallel to root surface, at approx right angel to extrinsic fibers

Question 13

Define the cementoenamel junction

Answer 13

The deposition of cementum differs amongst individuals at the CEJ

Question 14

What are 2 changes to the cementum?

Answer 14

1. Age related changes

2. Cemental repair

Question 15

What happens in age related changes?

Answer 15

Surface irregularity, narrowing of apical canal, reversal lines

Question 16

What happens in cemental repair

Answer 16

Cells are programmed to maintain the smooth surface of the root after resorption
-Defects arise because of traumatic occlusion, tooth movement, hyereruption

Question 17

What is concresence?

Answer 17

Union of root structure of two or more teeth by cementum. Can cause complications for extraction

Question 18

What is cementum caries?

Answer 18

Root surface caries, increases as gingival recession occurs, usually more prevalent in older adults and periodontal disease

Question 19

What is periodontal ligament?

Answer 19

Fibrous Connective trissue between alveolar process and cementum. Composed of fibers, cells and ground substance

Question 20

What is the PDL composed of?

Answer 20

Composed of connective tissues, fibers, cells and ground substance

Question 21

What is the function of PDL?

Answer 21

Provides for the attachment of the tooth to the surrounding alveolar bone through the cementum.
Is to permit the tooth to with stand the force of mastication

Question 22

What is the composition of PDL?

Answer 22

CT fibres, collagen fibers (sharpeys fibres), ground sustance, nerves,

Question 23

Name cells that are found in PDL

Answer 23

• FIBROBLASTS, OSTEOBLASTS (form new bone), CEMENTOBLASTS
• ENDOTHELIAL CELLS
• MACROPHAGES & OSTEOCLASTS
• EPITHELIAL RESTS
• UNDIFFERENTIATED MESENCHYMAL CELLS
• BLOOD CELLS

Question 24

Name the 4 types of fibres within the gingival group

Answer 24

ALVEOLOGIINGIVAL (free)
DENTOGINGIVAL (attached)
CIRCULAR/CIRCUMFERENTIAL FIBERS
DENTOPERIOSTEAL

Question 25

What is the function of the transeptal group?

Answer 25

The function of the interdental ligament is to resist rotational forces and thus hold the teeth in interproximal contact

Question 26

What subgroups are within the dentoalveolar group?

Answer 26

``` ALVEOLAR CREST GROUP HORIZONTAL GROUP OBLIQUE GROUP APICAL GROUP INTERRADICULAR GROUP ```

Question 27

What is the function of the dentoalveolar group?

Answer 27

In summation to resist tilting, extrusive and instrusive forces, rotational forces

Question 28

What is the alveolars crests function and where is it located?

Answer 28

Resist tilting, exstrusive forces and rotational. Dentoalveolar bone - loacted near cervical area, just below CEJ'

Question 29

What is the horizontal groups function and where is it located?

Answer 29

Dentolveolar group - resists tilting mesially, distally, palatally, buccally & rotational forces. Located from midroot to cementum

Question 30

What is the oblique group and where is it located?

Answer 30

Dentoalveolar group: resists instrusive forces, pushing tooth inwards, rotational forces. Located above apical zone upward toward alveolar bone

Question 31

What is the apical group and where is it located?

Answer 31

Dentoalveolar group: exstrusive forces, resist rotational forces, works with alveolar crest. Located apical of t root

Question 32

What is the Interadicular fiber group and where is it located?

Answer 32

Dentoalveolar group: extended beteen roots to alveolar bone proper

Question 33

Define Alveolar bone

Answer 33

Part of the maxilla and mandible, that supports the roots of the teeth, existence is dependent on teeth. Develops by intramembranous ossification

Question 34

What is the chemical composition of the Alveolar Bone?

Answer 34

60% inorganic (hydroxylapitie) 25% organic material 15% water

Question 35

What is the composition of the gross anatomy of the alveolar bone?

Answer 35

CORTICAL PLATE (buccal/lingual) • Compact bone with periosteum CRISBRISORM PLATE (socket wall): • Radiographically = lamina dura • Presence is indicator of health of PA tissues CANCELLOUS BONE • Spongy bone, trabeculae with bone marrow and spaces in between