PDL, Cementum and alveolar bone Flashcards
(93 cards)
1
Q
What does the periodontal ligament connect?
A
The tooth root to the inner wall of the alveolar bone
2
Q
What is the PDL composed of?
A
- Highly cellular CT
- Complex vascular tissue, communicates with the marrow spaces through vascular channels in the bone
3
Q
What is the width of the PDL on average?
A
0.2mm
4
Q
Smaller PDL is often associated with
A
unerupted or teeth not in function
5
Q
A wider PDL width is often associated with
A
teeth in hyperfunction
6
Q
How are the principal fibers arranged?
A
Collagen fibers arranged in bundles and follow a wavy course
7
Q
Principal fibers form what type of network between the tooth and the alveolar bone?
A
Continuous anastomosing network
8
Q
Principal fibers are primarily composed of what?
A
Type I collagen
9
Q
What does the type I collagen of the prinicpal fibers provide?
A
Tensile strength and elasticity
10
Q
What are sharpey’s fibers?
A
Terminal portions of the principal fibers that are inserted into cementum and bone
11
Q
What are the principal fibers synthesized by?
A
Fibroblasts
12
Q
Collagen biosynthesis occurs inside what?
A
The fibroblasts
13
Q
In addition to fibroblasts, collagen is also synthesized by what?
A
Chondroblasts, osteoblasts, odontoblasts and other cells
14
Q
What synthesizes tropocollagen molecules?
A
Fibroblasts
15
Q
Tropocollagen molecules aggregate into
A
microfibrils
16
Q
Microfibrils are packed together to form
A
Collagen fibrils
17
Q
The fibrils have a transverse striation caused by the
A
overlapping arrangement of the tropocollagen molecules
18
Q
Oxytalan fibers are a type of
A
elastic tissue
19
Q
Oxylatan fibers are synthesized by
A
fibroblasts
20
Q
What areas are oxytalan fibers found in?
A
Areas of body subjected to mechanical stress, like periodontal membranes and tendons
21
Q
How dot he oxytalan fibers run?
A
Parallel to the root surface in a vertical direction and bend to attach tot he cementum in the cervical third of the root
22
Q
What is the function of oxytalan fibers?
A
help in regulation of vascular flow
23
Q
What are types of cells in the PDL?
A
- CT cells
- Epithelial rest cells
- Immune system cells
- Cells associated with neurovascular elements
24
Q
What is the main cell type in PDL?
A
Fibroblasts
25
Fibroblasts are oriented along the
principal fibers
26
Fibroblasts phagocytize
old collagen fibers
27
Fibroblasts control collagen turnover via
enzyme hydrolysis
28
What are epithelial cell rests of Malassez?
Remnants of the hertwig root sheath
29
Epithelial cell rests of malassez form what?
Latticework in the PDL close to the cementum
30
Epithelial cell rests of malassez are interconnected by
hemidesmosomes and are surrounded by a distinct basal lamina
31
With age, what happens to Epithelial cell rests of malassez?
they degenerate and their number diminishes
32
What are the functions of Epithelial cell rests of malassez
- Cementum repair and regeneration
- May cause the formation of periapical cysts and lateral root cysts
33
What are the main components of ground substance?
- Glycosaminoglycans
- Proteoglycans
- Glycoproteins
- 70% water content
34
What are glycosaminoglycans?
Long, linear polysaccharides consisting of repeating disaccharide units adn include molecules like hyaluronic acid
35
What is the function of glycosaminoglycans?
Play important role in the cell signaling process, including regulation of cell growth, promotion of cell adhesion, and wound repair
36
What are glycoproteins?
Proteins that have carb groups attached to the polypeptide chain
37
What are types of glycoproteins?
- Fibronectin
- Laminin
-Undulin
38
What does fibronectin do?
Influences various biological processes like cell adhesion and migration, tissue repair, wound healing and development
39
What does laminin do?
Regulates cell differentiation, migration and adhesion
40
What does undulin do?
Plays a role in the structure and function fot he PDL
41
What are proteoglycan composed of?
consisting of a protein bonded to glycosaminoglycan groups
42
What do proteoglycans do?
- Help organize and regulate the ECM
(play role in various biological processes including adhesion, signaling, growth factor signaling, hydration and tissue development)
43
What are the physical functions of the PDL?
- Attach teeth to bone
- Provide soft tissue casing to protect vessels and nerves from mechanical forces
- maintenance of gingival tissues in their proper relationship to teeth
- Resistance to the impact of occlusal forces
- Transmission of occlusal forces to the bone
44
When alveolar bone has reached its limit from forced, the load is transmitted to what?
The basal bone
45
What is the tensional theory?
Prinicpal fibers are the major factor in supporting the tooth and transmitting forces to the bone. Fibers unfold and straighten and then transmit forces tot eh alveolar boen
46
What is the viscoelastic system theory
When forces are transmitted to the tooth, the extracellular fluid passes from the PDL into the bone marrow spaces through the foramina in the cribriform plate
47
How does the PDL deal with axial force?
- Root tends to be displaced into the alveolus
- Oblique fibers change from waby untensed pattern and assume full length
- Principal fibers sustaint he major part of the axial force
48
What are the phases of a horizontal or tipping force?
Phase 1: tooth moves within the confines of the PDL
Phase 2: Displacement of the facrial and lingual bony plates
49
When does the PDL perform formation and resorption of cementum or alveolar bone?
- Physiological tooth movement
- Accomodation to the periodontium to occlusal forces
- Repair of injuries to the periodontal tissues
50
There is a high turnover rate of colalgen in the periodontal ligament. The rate of colalgen synthesis in the PDL is
- Twice as fast as in the gingiva
- Four times as fast as in the skin
51
What is cementum?
Calcified avascular mesenchymal tissue
52
What is cementum composed of?
Collagen fibrils, calcified interfibrillar matrix and cementocytes
53
What are intrinsice fibers synthesized by?
Cementoblasts
54
Intrinsic fibers constitute the
cementum matrix
55
Extrinsic fibers are the portion fo the principal periodontal fibers that are
embedded in the cementum
56
Extrinsic fibers are synthesized by
fibroblasts
57
Interfibrillar ground substance of cementum is composed of what?
Noncollagenous components: proteoglycans, glycoproteins and phosphoproteins
58
What is the function of Interfibrillar ground substance of cementum?
Regulation of the cell-cell and cell-matrix interactions, during normal development of cementum and during the regeneration of cementum
59
Interfibrillar ground substance of cementum are synthesized by what?
Cementoblasts
60
Cementoblasts originate from the
dental follicle
61
Cementoblasts are located along
the outer layer of the PDL
62
When entrapped in cementum, the cementoblasts
lose their secretory activity and become cementocytes
63
Cementocyte lies in
a lacuna
64
Acellular cementum does not
contain cementocytes
65
Cellular cementum is ______ than acellular cementum
thicker
66
What is acellular afibrillar cementum?
Only ground substance
67
Where is acellular afibrillar cementum present?
In coronal cementum
68
What is acellular extrinsic fiber cementum?
No cells, have fibers from fibroblasts and cementoblasts and ground substance
69
Where is acellular extrinsic fiber cementum found?
In cervical thrid of root, but may extend apically
70
What is cellular mixed stratified cementum?
Cells, fibers from both fibroblasts and cementoblasts
71
Where is cellular mixed stratified cementum found?
Mainly in apical third of roots and apices and in the furcationa reas
72
What is cellular intrinsic fiber cementum?
Cells and intrinsic fibers from cementoblasts
73
Where is cellular intrinsic fiber cementum?
Fills the resorption lacunae
74
Where is cementum thickenss greatest?
At the apical third of the root and in the furcation areas. and in distal rather than mesial
75
Cemental aplasia
absence of cementum
76
Cemental hypoplasia
paucity of cementum
77
Cemental aplasia and hypoplasia increase the risk of
periodontitis and tooth loss
78
Cemental hyperplasia or hypercementosis
excessive deposition of cementum
79
Cementum resorption occurs mostly in
apical third of the root
80
Systemic factors of cementum resorption
Calcium deficiency, hypothyrodism, hereditary fibrous osteodytrophy and Paget's disease
81
What are some local factors that cause cementum resorption?
Trauma from occlusion, orthodontic movement, pressure from malalignes erupting teeth, cysts, tumors, teeth without functional antagonists, impacted teeth,
82
Cementum repair requires the presence of
viable connective tissue and cementoblasts
83
Cementum repair will not occur if
epithelium proliferates into an area of cementum resorption
84
What is cementum formation and repair important for?
- Development of the periodontium
- Regeneration of lost periodontal tissues
85
What is ankylosis?
Fusion of cementum and alveolar bone with obliteration of the periodontal ligament (Resoprtion of root and replacement by bone)
86
Ankylosis diagnostic criteria
- Root resorption
- Teeth fo not have physiologic mobility
- Physiologic drifting and eruption of teeth do not occur
- Proproception is lost
87
Systemic factors that lead to remodeling of alveolar bone
Changes in PTH, calcitonin, vitamin D3, certain systemic diseases, medications
88
Describe the sequence of events in the process of bone resorption
1- attachment of osteoclasts to the mineralized surface
2-Creation of sealed acidic environment through the action of proton pump, which demineralized bone and exposes organic matrix
3- degradation of exposed matrix to its constituent AA via the action of released enzymes
4- sequestering of mineral ions and AA within the osteoclast
89
What is the periosteum?
a differentiated osteogenic CT that cover bone surfaces
90
Periosteum consists of
Inenr layer composed of osteoblasts surrounded by osteoprogenitor cells, which have the potential to differentiate into osteoblasts
- Outer layer composed of colalgen fibers and fibroblasts and is rich in BVs and nerves
91
What is the endosteum composed of?
- inner osteogenic layer consists of a single layer of osteoblasts
- Outer layer composed of small amount of fibrous tissue
92
What is fenestration?
Root surface is denuded of bone and is covered only by periosteum and gingiva. Marignal bone is intact
93
What is dehiscence?
Root surface is denuded of bone and is covered only by periosteum and gingiva. Denuded area extends through the marginal bone
