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Anatomy > Anatomy - Outcome 8 > Flashcards

Anatomy - Outcome 8 Flashcards

1
Q

Location of Cementum

A

covers root surface

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2
Q

Physical Characteristics of Cementum

A

Colour:
yellowish, clinically unable to distinguish from dentin

Thickness:
1 hair - coronal - 10-50 microns
thicker apically - 50 to 200 microns

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3
Q

Chemical Composition of Cemetum

A

-cemetum is the softest of the hard tooth surfaces
-like enamel and dentin, cementum is composed of an organic mix containing crystallized mineral substances
-Inorganic material - 65%
-Organic material - 23%
-Water - 12%

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4
Q

Histologic Structure of Cementum

A

Organic Matrix:
-collagen fibrils and ground substance (like dentin) which mineralize
-may contain whole cells (dentin only contains cell process)
-forms in layers

Cementoblasts
-in PDL
-form cementum
-same cells embedded in cementum
-called cementocytes

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5
Q

Formation of Cementum:

A
  1. Forms in layers:
    -cementoblasts start at CEJ
    -calcified ground substance (higher water concentration)
    -thicker apex, become surrounded in cementum
  2. As it is laid down it assumes one of 3 relationships with enamel:
    -overlap at CEJ - 60%
    -meets CEJ - 30%
    -does not meet CEJ - 10%
    -sensitivity issue
    -exposure of dentinal tubules
  3. Lacuna(e)
    -spaces in cementum - cementocyte
    -canaliculi - cytoplasmic projections in small canals - communication
  4. Acellular cementum
    -thin coronal cemetum
    -no cells
    -top 1/2-1/3 of root
  5. Cellular cementum
    -apical 1/3
    -contains cementocytes
    -new cementum laid down
  6. Cementoid
    -the outer surface toward PDL
    -newest cementum layer
    -less mineralized - not destroyed easily by osteoclasts
    -importance in orthodontics *cemeontoid protects the root from osteoclasts which destroy bone for tooth movement
  7. Sharpey’s fibers
    -ends of PDL embedded in developing cementum
    -firmly attach PDL to tooth
    -PDL attached to the bone
    -suspension of the tooth in the socket
  8. Hypercementosis - not fully understood
    -Cementum Hyperplasia
    *thickening of cellular cementum
    *in cellular cementum
    *extraction issues
  9. Cementicles
    -small calcifications in PDL
    -no clinical significance
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6
Q

Clinical Importance of the Cementum Structure (Function)

A
  1. Anchors tooth to the bony socket
    -Sharpey’s fibers
    -suspended by PDL
    -no cementum - no attachment
  2. Compensation for loss of enamel
    -produced intermittently through life
    -by cementoblasts
    -loss of crown length due to tooth wear
    -slight tooth movement upward
    -attempt to maintain mx/mn occlusion
  3. Repairs damaged root
    -dentin resorbed/destroyed due to injury
    -lateral pressures may cause root damage
    -if not severe, new cementum laid down
    -eg. impacted wisdom tooth
  4. Role in Orthodontics
    -lateral pressure to move a tooth
    -tension on PDL and bone
    -pull tension creates the formation of bone (osteoblasts)
    -pressure tension creates bone destruction (osteclasts cementoid)
    -tooth movement
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7
Q

Structure of Periodontal Ligament (PDL) - Location

A

-a layer of connective tissue which surrounds the root of a tooth
- main suspensory tissue
-connections with cementum, bone and connective tissue of gingiva

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8
Q

Structure of Periodontal Ligament - Physical Characteristcs

A

-0.1 - 0.38 mm in width
-Has all the components of connective tissue
*intercellular substance
*cells
*fibers
-Has vascular supply, lymphatic and nerve supply

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9
Q

Structure of Periodontal Ligament - Histologic Structure

A

-mesodermal cells of dental sac
-development after cementum
-fibroblast cells become PDL fibers
-Sharpey’s Fibers - cementum & bone

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10
Q

Formation of the Periodontal Ligament

A
  1. Periodontal Ligament ← mesodermal cells of the dental sac.
  2. Periodontal ligament begins developing after cementum has begun forming.
  3. As dental sac cells begin to change, they first become fibroblasts and these eventually become collagen fibers which in turn will become periodontal ligament fibers. Initally, PDL fibers are arranged around the tooth and parallel with the root surface.
  4. As the tooth moves towards the oral cavity, gradually a functional orientation of the fibers takes place.
    *instead of loose and irregularly arranged fibers, fiber bundles extend from the bone to the tooth
    *majority of PDL fibers attach from tooth socket bone to cementum of the tooth
    *exception: around the cervical area (CEJ), fibers attach from cementum to gingival that surrounds the adjacent tooth or to the cementum of the adjacent tooth
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11
Q

While the PDL is forming, other components are forming at the same time:

A

a. Blood Vessles
-enter through the bone at various locations
-superior and inferior alveolar artery and vein

b. Lymphatic Vessels
-follow the path of the blood vessels

c. Nerves
-sensory
-provide a sense of touch and pressure
-generally follow blood vessels as well

d. Rests of Malassez
-groups of epithelial cells
-role in cysts/tumors

e. Cementicles
-calcified bodies
-no clinical significance

f. Osteoblasts & Cementoblasts
-bone and cementum forming
-specialized connective tissue cells

g. Osteoclasts & Cementoclasts
-bone and cementum destroying (resporption)
-specialized connective tissue cells

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12
Q

Gingival Fiber Groups

A
  1. Free Gingival Fibers
  2. Transseptal Fibers
  3. Alveolar Crest Fibers
  4. Horizontal Fibers
  5. Oblique Fibers
  6. Apical Fibers
  7. Interradicular Fibers
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13
Q

Free Gingival Fibers

A

-cementum to frere gingiva
-hold gingiva against tooth
-fibers pull taut with occlusal forces
-go all around the tooth

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14
Q

Transseptal Fibers

A

-below gingival fiber group
-mesial and distal only
-extend cementum of one tooth to the cementum of adjacent tooth
-hold teeth in relation to each other

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15
Q

Alveolar Crest Fibers

A

-cementum to the crest of bone
-resist horizontal movement

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16
Q

Horizontal Fibers

A

-below alveolar crest fibers
-move parallel to the occlusal plane
-resist horizontal movement

17
Q

Oblique Fibers

A

-diagonal direction
-bone attachment higher than cementum
-resist occlusal pressure

18
Q

Apical Fibers

A
  • root apex
    -prevent vertical forces (extraction) and tinting
19
Q

Interradicular Fibers

A

-furcation
-stabalize tooth
-molars only

20
Q

Clinical Importance of the Periodontal Ligament (the Functions)

A
  1. Supportive
    -any pressure results in a pull tension
    -maintain suspended in the socket
    -forces spread out - equal distribution
    -damage
    -stretching
    -temporary tooth movement
  2. Sensory - determine pressure and touch
  3. Nutritive - extensive blood supply
  4. Formative
    -produce cementum and bone during tooth development
    -cementoblasts - produce secondary cementum in an adult tooth
    -fibroblasts and fibroclasts for tooth movement
  5. Resorptive
    -pressure tension
    -causes resportion of bone and possibly PDL
21
Q

Overall Importance of Periodontal Ligament

A

-keep tooth retained in socket

  • repaired if localized destruction
  • re-attachment after excessive pressure removed
  • extensive destruction - tooth removal
22
Q

Alveolar Bone - Gross Structure (organ & tissue)

A
  1. Cortical bone
    -surface bone
    -compact bone
  2. Trabecular / Spongy bone
    -cancellous
    -inside of bone
    -surrounds bone marrow
  3. Design
    -gives strong structure (cortical)
    -lightweight (trabecular)
    -strong blood supply (bone marrow)
    -covered by periosteum for muscle and CT attachment
23
Q

Alveolar Bone - Microscopic Structure

A

-60% mineralized
-25% organic
-15% water
-hydroxyapatite matrix
-approximately the same hardness as cementum

24
Q

Osteoid (bone matrix)

A
  1. Osteoblasts (Bone forming cells)
    -produce osteoid
    -allows remodelling of bone
    -repair of injured bone
    -osteoclasts - originate from osteoblasts, function in resorption of bone

Osteocytes - mature osteoblasts trapped in bone matrix

Lacuna
-small space surrounding osteocyte in bone matrix
-connected canaliculi - tubular canals in bone

25
Q

Bone Tissue

A

formed in thin layers called lamellae

26
Q

Bone tissue: Haversian System

A

-lamellae are arranged in circles with central canal (Haversian Canal) containing blood vessels

-canaliculi - connect with canal allowing for transport of nutrients throughout the bone tissue

27
Q

Bone Tissue: Lamellar System

A

-bone in thin layers follow the surface of the bone (not in concentric circles)

-transport by canaliculi

-makes up surface bone - cortical and surface of trabecular bone

28
Q

Bone Tissue: Vascularity

A

-bone is very vascular
-high communication and transport through many canals and systems

29
Q

Bone Tissue: Bone Marrow

A

-center of bones
-red marrow - contains red and white blood cells
-yellow marrow - fat, older bones increases

30
Q

Bone Tissue: Formation & Resporption (Growth of bone)

A

-bone is continually resorbed and reformed through life
-osteocytes in lacuna become osteoblasts/clasts as required
-more development in growing years
-orthodontics - successful at all ages

31
Q

Periosteum

A
  • The outside surface of bone is covered by tough connective tissue membrane called the periosteum
32
Q

Endosteum

A

A thinner delicate connective tissue covers the inner surface of compact bone and trabeculae is called endosteum

33
Q

Alveolar Process

A

-Part of the maxilla and the mandible that surronds and supports the tooth

-alveolar crest - located near the cervix of the tooth

  • cortical plates on outside all of maxilla and mandible

-trabecular bone in between

  • lamina dura lines tooth socket (cortical-like bone)
34
Q

Clinical Significance of the Alveolar Process: Orthodontics

A

-bone vascular, living tissue
-allow for destruction and formation of bone for tooth movement
-movement too fast may result in irreverrsible bone and/or root resorption

35
Q

Clinical Significance of the Alveolar Process: Periodontal Disease

A

-plaque and calculus in the sulcus
-inflammation of surrounding tissues
-destruction of PDL and attaching bone (lamina dura) in the alveolar crest
-eventual tooth loss
-repair of some when infection removed, however, not to the original height of alveolar crest (increase pocket depth)

36
Q
A

Anatomy (34 decks)

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