1/30 Histology of Cementum and Alveolar Bone Reading Flashcards
1
Q
Tissues that contribute to root development:
A
dental papilla, enamel organ, dental follicle
2
Q
Where do the cells of the OEE contact the IEE?
A
cervical loop (base of the enamel organ)
3
Q
Cervical loop becomes:
A
root sheath cells after it grows away from the crown
4
Q
How do inner root sheath (IRS) cells cause root formation?
A
inducing cells of dental papilla to become odontoblasts –> root dentin
5
Q
What dictates whether a tooth will be single or multi- rooted?
A
root sheath
6
Q
remainder of cells of dental papilla become:
A
pulp
7
Q
tissue that surrounds enamel organ, dental papilla and root:
A
dental follicle
8
Q
The dental follicle will become:
A
cementum, PDL, and surface layer of alveolar bone
9
Q
What initially encloses the developing crown?
A
alveolar bone
10
Q
How do PDL fibers attach to the root?
A
via cementum (alveolar bone –> PDL fibers –> cementum)
11
Q
What can be found at the base of the cervical loop after crown completion?
A
IEE and OEE
12
Q
After crown completion the I and O EE form:
A
bilayer of epi cells called the Hertwig’s root sheath
13
Q
1st formed part of the epi root sheath (ERS) that bends upward at a 45’ angle?
A
epi diaphragm (disc-like structure)
14
Q
Function of epi diaphragm:
A
reduces size of the apical foramen
15
Q
How does he epi diaphragm maintain a constant size during root development?
A
bc of the continuity of the rooth sheath grows in length at the angle of the diaphragm and not at its tip
16
Q
This induces cells of dental papilla to differentiate to odontoblasts which form root dentin:
A
newly formed vertically disposed of part of the ERS
17
Q
Does the crown move toward or away from the base of the crypt with increased root length?
A
away from the base of th crypt
18
Q
What provides space for continued root growth?
A
uplifting of the tooth with inc root length
19
Q
How does the position of the epi diaphragm alter in relation to the base of the crypts during development?
A
it doesn’t, it maintains its position
20
Q
TF? The root lengthens at the same rate as the tooth moves occlusally.
A
T
21
Q
Name the layers in root development, in to out:
A
pulp, epi diaphragm, ERS cells, Enamel space, REE, dental follicle
22
Q
How does the formation of a single rooted tooth occur?
A
growth of root sheath followed by development of root dentin
23
Q
What differentiate into odontoblasts to form dentin?
A
dental papilla
24
Q
What happens as the 1st layer of dentinal matrix mineralizes?
A
root sheath cells separate from surface and breaks occur in it
25
What cause the breaks in continuity of ERS cells?
degeneration of epi cells
26
What happens to ERS cells after they separate from surface of root dentin?
migrate to follicular area, mesen- or ectomesenchymal cells of follicle migrate bw epi cell groups to contact root surface
27
What happens to mesenchymal or ectomesenchymal cells once they reach the root surface?
differentiate into cementoblasts, secrete cementum matrix (cementoid)
28
cementum matrix:
cementoid
29
This will mineralize to form cementum:
cementoid
30
How do the cells of the root sheath persist?
In the developing PLD as Malassez's epi rests
31
How does root elongation progress?
w proliferation of remaining root sheath cells at the base of the angle of the epi diaphragm, along w proliferation of adjacent cells of the dental papilla and dental follicle
32
This allows for space for further root development as the root lengthens:
compensatory movement of eruption
33
When is the root sheath seen as a complete layer?
never
34
When does the root sheath break down?
once root dentin begins to form
35
Last part of the root sheath to degenerate after root completion:
epi diaphragm
36
TF? root development continues after tooth eruption.
T
37
Functions of root sheath:
initiate root development, determine size, length, and shape of root
38
Interruption of the root sheath can lead to:
root deformities
39
Root trunk:
bw cervical enamel and area at which roots divide
40
How does division of the root take place?
differential growth of the root sheath
41
How are multiple roots formed?
tongue-ike extensions develop in the area of the epi diaphragm, grow until contact w 1 or 2 opposing extensions that fuse w each other, epi proliferates at an equal rate at perimeter of each opening and forms epi diaphragms and cuffs to map the ind roots as they elongate
42
Areas of contact of the tongue-like extensions form:
epi bridges at furcation zone
43
A 3 rooted tooth arises form how many tongue-like projects?
3
44
Odontoblast differentiation occurs here:
bifurcation zone
45
What induce formation of odontoblasts at each bridge?
inner ERS cells, produces a span of dentin bw and around each root
46
Dentin formation follows:
root sheath
47
Odontoblasts differentiate along the coronal pulp ___
floor
48
What does the degeneration of some root sheath cells allow for?
space for cementoblasts to deposit cementum on the root surface
49
If continuity of root sheath were broken before dentin formation what could happen?
missing or defective epi cells, odontoblasts won't differentiate, dentin would not form opposite defect in root sheath, small lateral canal, PDL to main canal (accessory canal)
50
Most common location of accessory canals:
apical 3rd
51
TF? Accessory canals can form anywhere along the root.
T. (check? didn't we learn in endo that to be called an accessory canal it had to be in the apical 1/2 of the canal?)
52
Defects in furcation areas are due to:
incomplete fusion of the tongue-like projections of epi diaphragm, accessory canals seen here
53
Result of failure of the ERS to degenerate at the proper time:
remains adherent to the surface of the root dentin, mesenchymal cells of the dental follicle will not come into contact with the dentin, no differentiation into cementoblasts, no cementum formation, areas of root devoid of cementum
54
Portion of the root in which areas of exposed root dentin can be found:
anywhere
55
most common site of areas of exposed root dentin:
cervical zone (causes sensitivity after recession?)
56
Result of ERS remaining adherent to dentin in the cervical area near the furcation zone:
inner cells of root sheath --> functional ameloblasts --> enamel pearls
57
Common site of enamel pearls:
bw roots of permanent molars
58
What would happen if the ERS becomes dislocated after partial root mineralization?
twisted or bent roots --> dilaceration or root distortion, more often permanent teeth
59
Typical cause of dilaceration or root distortion:
blow on a deciduous predecessor resulting in displacement of underlying, partly mineralized permanent tooth
60
Possible effects of a dilacerated root:
prevention of eruption, ortho and extraction problems
61
ERS is aka:
Hertwig's Sheath
62
When does the ERS break down and migrate away fromt he dentinal surface?
after dentin formation
63
What become the epi rests of Malassez?
remnants of the ERS
64
How long do the epi rests of malassez persist?
throughout life
65
epi rests of malassez are often found here in youth up to 20yo
apical zone
66
After 20yo, where are epi rests of malassez most often found?
cervical areas
67
Inherent characteristics of epi cells:
moving toward surface and exfoliating
68
Some epi remnants of root sheath may get trapped in bay-like depressions bw dentin and cellular cementum, forming:
enameloid or intermediate cementum
69
TF? Accessory canals can spread infections from the PDL space but not vice versa.
F. Can spread in both directions
70
appear as network of epi strand along root surface, as isolated islands of cells surrounded by CT OR as isolated cells in close contact with cementum
epi rests
71
3 types of epi rests:
proliferating, resting, and degenerating (dividing, inactive, undergoing lysis)
72
Epi rest cells are surrounded by:
basal lamina and hemidesmosomes
73
Morphology of epi rest cells:
few irregularly shaped cells w ovoid, oblong, or indented nuclei, dense cytoplasm, mito, ribosomes and tonofilaments occuring singly or in bundles, anchored to attachment plaques at sites of hemi- or desmosomes
74
Appearance of epi cells when singly present:
uniform shape, surrounded by basal lamina, smooth, round nucleus outline
75
What can cause epi rests to proliferate into cysts or tumors?
inflammation or other pathology
76
degenerated epi cells can form:
a nidus for calcified bodies --> formation of cementicle in PDL
77
physiological role of epi rests:
unknown
78
Behavior of epi rests cells is:
species dependent - collagen degradation in rat incisors that grow throughout life
79
Function of procine (hog) epi rests:
phagocytose collagen
80
ectomesenchymal condensation, initially surrounds enamel organ and enclosed dental papilla:
dental follicle (sac)
81
What does the dental follicle later surround?
the crown, then root
82
cells that initiate development of supporting tissues of tooth:
dental sac cells
83
From where do dental sac cells arise?
near OEE, migrate peripherally
84
Cells of the dental sac give rise to:
cells that produce the cementum, the PDL, and the alveolar bone (crypt or alveolus)
85
What controls the formation of future periodontal structure and first appears in very early developmental stages?
dental follicular cells
86
Teeth are protected and stabilized at all stages by:
follicular tissue
87
epi rest cells are connected via:
desmosomes
88
sac cells migrate from:
the enamel organ to initiate periodontal development
89
Relationship of tooth germs of permanent teeth and their deciduous predecessor
they are in the same dental sac
90
When are tooth germs of permanent teeth and their deciduous predecessor no longer in same sac?
deciduous tooth eruption, permanent develop separate sacs in separate crypts
91
Crypt:
bony cavity enclosing a developing tooth, formed by the dental sac
92
Opening in crypt roof:
dental sac fibers extend, communication with oral mucosa
93
Fibrous extension of dental sac, connects permanent tooth germ to oral mucosa:
gubernacular cords, not found in deciduous dentition?
94
gubernacular cords are formed of:
fibrous tissue, extensions of the tooth sac, may contain epi cells, possibly remnants of the dental lamina
95
What can form epi pearls, epi nest cells, or cysts (keratinized materials)?
remnants of dental lamina
96
What initially surrounds the young tooth?
dental sac
97
What becomes the supportive tissue as the tooth erupts?
follicular tissue
98
List the supportive tissues of the tooth:
cementum, PDL, and supporting alveolar bone
99
Functions of dental sac:
protect/ stabilize tooth during formation/ eruption, nutrition, nerve supply, give rise to cementum, PDL, and inner wall of bony crypts or alveolus
100
Regulates function of follicular cells?
autocrine and paracrine action of local factors: prostaglandins, EGF, TGF, etc.
101
What would happen with the removal of the dental follicle?
No eruption
102
Formative cells in supporting tissue are important in:
initiation, formation, and maintenance of these tissues
103
What happens just before degeneration of ERS?
root dentin deposited adjacent to it (thin, amorphous, structureless, highly mineralized secretion on root dentin surface, no collagen, has tryptophan (also found in enamel matrix)
104
intermediate cementum more common here:
apical root, avg thickness: 10-20um
105
What forms the intermediate cementum secretion?
ERS cells just before they break up and migrate from root surface
106
Function of intermediate cementum secretion:
attach 2' cementum to its surface
107
TF? intermediate cementum secretion sometimes contains epi cells.
T
108
Functions of root sheath cells:
stimulate odontoblasts, possible secretory function in producing the intermediate cementum
109
When does cementum formation begin?
intermediate cementum is contacted by ectomesenchtmal cells of dental follicle, after root sheath migration
110
The cementum that covers the roots functions to:
attach the PDL fiber bundles
111
Relative rate of cementogenesis root dentinogenesis:
cementogenesis is slower
112
Cementoblasts have features that are characteristic of:
cells capable of protein synthesis and secretion, well developed, rough-surfaced ER, notable Golgi apparatus, many mito, large nucleus w prominent nucleoli, abundant cytoplasm
113
Matrix (cementoid) components:
collagen fibers, ground substance w proteoglycans & glycoproteins
114
These cells first make the organic matrix or cementoid:
newly differentiated cementoblasts
115
Proteoglycans consist of:
GAGs, predominance of sulfated type attached to core of protein
116
Collagen fibers produced by cementoblasts:
intrinsic fibers, run parallel to cementum surface in an irregular manner
117
When do cementoblasts enter a quiescent state?
Once layered cementum is thick enough
118
Location of cementoblasts when they enter quiescent state:
cementum front
119
provides attachment, tooth to bone:
Collagen fibers embedded in cementum matrix, produced by fibroblasts
120
Embedded portions of the PDL fibers in the cementum:
perforating fibers OR Sharpey's fibers, extrinsic fibers of the cementum, right angles to root surface (intrinsic made by cementoblasts)
121
Difference bw cellular and acellular cementum:
cells in matrix
122
What determines the type of cementum formed:
cementoblasts behavior during matrix formation
123
When does cellular cementum develop?
When cementoblasts making matrix get embedded in matrix as cementocytes (can't retreat to PDL)
124
When does acellular cementum develop?
when all cementoblasts retreat into PDL, leaving no trapped cells behind
125
Acellular cementum is generally found here:
cervical half, cellular apical half
126
TF? Layers of cellular and acelluar cementum may alternate at any site.
T
127
In this type of cementum, trapped cementoblasts develop cytoplasmic processes and reside in the cementum matrix to become cementocytes:
cellular
128
When does alveolar bone develop?
as tooth develops
129
Alveolar bone initially forms:
tooth crypt, thin eggshell of support around each tooth germ
130
TF? Alveolar bone growth keeps pace with root lengthening.
T
131
Development of the alveolar paocess begins in the __th wk in utero.
8th
132
Alveolar bone develops a horse-shoe groove in this week of development
8th wk in utero
133
What forms the horse shoe groove/ bony groove/ canal?
facial / lingual plates of body of man and max
134
What does the bony groove contain?
developing tooth germs, alveolar blood vessels, nerves
135
Developing tooth germs first lie here:
free in the grooves, septa then form bw teeth to make separate crypts
136
alveolar process develops during:
eruption
137
What forms the dental alveolus in uterine life?
embryonic bone type, made of tiny, bony spicules
138
2 types of embryonic bone
woven, coarse bundle
139
Which type of embryonic bone contains collagen bundles in their matrix?
both
140
Main difference bw the 2 types of embryonic bone:
Woven: collagen bundles in various directions, coarse bundle bone: thicker collagen bundles, usually parallel in matrix
141
Does matrix of embryonic bone contain more or less GAGs and glycoproteins than mature?
more
142
embryonic bone is gradually replaced by:
mature/ lamellar bone, compact or spongy
143
Mature bone:
ordered layers (lamellae), fine fiber arrangement, fewer cells, uniform density, matrix stains evenly and lightly
144
Bone bw roots of teeth:
interdental septum
145
Bone bw roots of multirooted teeth:
interradicular bone/ septum
146
2 parts to mature, alveolar bone:
alveolar bone proper and the supporting bone
147
Thin lamella of compact bone. lines root socket w embedded periodontal fibers:
alveolar bone proper aka lamina dura
148
alveolar bone proper, aka:
lamina dura
149
What is the supporting bone made of?
both spongy and dense (compact), lamina dura: only compact
150
Function of supporting bone:
support alveolar bone proper
151
What is the cortical plate?
covering of mandible or maxilla
152
What furnishes compact portion of supporting alveolar bone?
cortical plate
153
Specialized type of dense bone made of bundle bone and Harvesian bone, RGO:
alveolar bone proper, aka lamina dura
154
Why is it called bundle bone:
penetrated PDL fibers bundles
155
Forms alveolar bone proper:
osteogenic cells of outermost layer of dental sac that differentiate to osteoblasts and lay down bone matrix or osteoid in which some osteoblasts become embedded as osteocytes
156
Cell-cell communication in bony tissue systems to place via these 3 means:
gap junctions, cytoskeleton (opposing points of adjacent cells), small nerve fibers in periosteum, multiple can work together
