W8 Peridontium, Cementum, Alveolar bone Flashcards
Define the periodontum
Collectively refers to the cementum, alveolar bone, and periodontal ligament
Define Cementum
In health is not visible, no nerve supply, avascular, recieves nutrition from PDL space
What is the function of the peridontium?
- Covers root surface
- Seal for dental tubules
- Attachment for the periodontal ligament fibers that hold tooth in socket
What is the chemical matrix of cementun?
Inorganic: 40-50% calcium hydroxyapatite
Organic: 50-55% Collagen fibres
- Bound water
What are the physical properties of cementum?
- 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
How can cementum be classified?
- Presence or Absence of Cells (acellular or cellular)
- Nature of Organic Matrix fibers (extrinsic or intrinsic
- Combination of 1 &2
Define Acellular cementum
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
Define Cellular Cementun
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
Define cementocyte
cementum cells, located with in the cellular cementum
Define odontoblasts
Form new cementum
What are extrinsic fibers?
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.
Define Intrinsic Fibers
Derived from cementoblasts, parallel to root surface, at approx right angel to extrinsic fibers
Define the cementoenamel junction
The deposition of cementum differs amongst individuals at the CEJ
What are 2 changes to the cementum?
- Age related changes
2. Cemental repair
What happens in age related changes?
Surface irregularity, narrowing of apical canal, reversal lines
What happens in cemental repair
Cells are programmed to maintain the smooth surface of the root after resorption
-Defects arise because of traumatic occlusion, tooth movement, hyereruption
What is concresence?
Union of root structure of two or more teeth by cementum. Can cause complications for extraction
What is cementum caries?
Root surface caries, increases as gingival recession occurs, usually more prevalent in older adults and periodontal disease
What is periodontal ligament?
Fibrous Connective trissue between alveolar process and cementum. Composed of fibers, cells and ground substance
What is the PDL composed of?
Composed of connective tissues, fibers, cells and ground substance
What is the function of PDL?
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
What is the composition of PDL?
CT fibres, collagen fibers (sharpeys fibres), ground sustance, nerves,
Name cells that are found in PDL
- FIBROBLASTS, OSTEOBLASTS (form new bone), CEMENTOBLASTS
- ENDOTHELIAL CELLS
- MACROPHAGES & OSTEOCLASTS
- EPITHELIAL RESTS
- UNDIFFERENTIATED MESENCHYMAL CELLS
- BLOOD CELLS
Name the 4 types of fibres within the gingival group
ALVEOLOGIINGIVAL (free)
DENTOGINGIVAL (attached)
CIRCULAR/CIRCUMFERENTIAL FIBERS
DENTOPERIOSTEAL
What is the function of the transeptal group?
The function of the interdental ligament is to resist rotational forces and thus hold the teeth in interproximal contact
What subgroups are within the dentoalveolar group?
ALVEOLAR CREST GROUP HORIZONTAL GROUP OBLIQUE GROUP APICAL GROUP INTERRADICULAR GROUP
What is the function of the dentoalveolar group?
In summation to resist tilting, extrusive and instrusive forces, rotational forces
What is the alveolars crests function and where is it located?
Resist tilting, exstrusive forces and rotational. Dentoalveolar bone - loacted near cervical area, just below CEJ’
What is the horizontal groups function and where is it located?
Dentolveolar group - resists tilting mesially, distally, palatally, buccally & rotational forces. Located from midroot to cementum
What is the oblique group and where is it located?
Dentoalveolar group: resists instrusive forces, pushing tooth inwards, rotational forces. Located above apical zone upward toward alveolar bone
What is the apical group and where is it located?
Dentoalveolar group: exstrusive forces, resist rotational forces, works with alveolar crest. Located apical of t root
What is the Interadicular fiber group and where is it located?
Dentoalveolar group: extended beteen roots to alveolar bone proper
Define Alveolar bone
Part of the maxilla and mandible, that supports the roots of the teeth, existence is dependent on teeth.
Develops by intramembranous ossification
What is the chemical composition of the Alveolar Bone?
60% inorganic (hydroxylapitie)
25% organic material
15% water
What is the composition of the gross anatomy of the alveolar bone?
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
