Enamel, Dentin, and Pulp Flashcards
1
Q
the most highly mineralized tissue in the body, consisting of more than 96% inorganic material in the form of apatite crystals and traces of organic material.
A
Enamel
2
Q
Why is enamel so hard
A
Withstand large masticatory forces (complex organization of matrix)
Withstand acids (mineralization)
3
Q
Explain thickness of enamel at diffent parts of tooth
A
- Thickest on coronal surface of crown
- Tapers in thicknest down to the CEJ
4
Q
What is the thickness of enamel in the incsical ridge of incisors?
A
2mm
5
Q
What is the thickness of enamel in the Cusp of pre-molar?
A
2.3-2.5mm
6
Q
What is the thickness of enamel in the Cusp of molar?
A
2.5-3mm
7
Q
How does the enamel of posterior teeth develope?
A
Cusps of posterior teeth begin as separate ossification centers, which form lobes that coalesce.
8
Q
What is the mineralization and matrix of the enamel (3 things)
A
- Hydroxyapatite= 90-92%
- Organic matrix proteins = 1- 2%
- Water = 4- 12%
9
Q
When conducting a filling, how much do you cut?
A
MUST cut past the enamel so that the material can adhere to the dentin.
10
Q
The enamel is cellular or acellular?
A
Acellular it CANNOT be regenerated
11
Q
The enamel is composed (structurally) of what 3 main things?
A
1.Enamel Rods
2. Enamel interods
3. Rod Sheaths
12
Q
A
13
Q
The tennis racket like structure that make up the enamel
A
Enamel rod
ROunded = stronger than square
14
Q
Explain the postioning of the head and tail of the enamel rod.
A
Rounded Head= more incisal occlusally
Tail= more cervicall
15
Q
The sturctures filling the gaps in bewteen enamel rods
A
Enamel Interrods
16
Q
What are these?
A
Enamel rods and minerals within.
17
Q
What are the two arrows pointing at?
A
- Enamel Rod
- Interod
18
Q
Where does eache enamel rod extend from to where?
A
From DEJ to exterenal surface of teeth.
* Perpendicular from DEJ , **except in cervical region of permanent teeth cause theyre vertical **
19
Q
Explain trend in enamal rod thickness
A
- At DEJ 4um
- At outer surface 8um
thicker on outer surface
20
Q
Groups of enamel rods entwine with adjacent groups of rods, following a curving irregular path toward tooth surface.
A
Gnarled Enamel
21
Q
Label
A
- 1= enamel
- 1a= gnarled enamel
- 2= dentin
- 3= dental pulp
- 12= gingiva
22
Q
Changes in direction of enamel prisms produce an optical appearance called
waves in enamel
A
Hunter-Schreger bands
23
Q
WHat is this?
A
Hunter-Schreger bands
24
Q
- Hypomineralized structures of enamel rods and rod sheath.
Project between adjacent groups of enamel rods. - Arise in dentin, extend from DEJ into the enamel in direction of long axis of crown
A
Enamel Tufts
25
What is arrow pointing at?
Enamel Tufts
26
Why is it that enamel tufts may play a role in dental caries?
**Not as mineralized** so less combative of acids released by bacteria = wear out first.
Allows caries to extend all the way to the DEJ
27
extend for varying depths from the **surface of enamel** and consist of linear, longitudinally oriented defects filled with organic material.
**Thin, leaf-like faults**
* A weak area predisposing a tooth to entry of bacteria and caries.
* Mostly organic material
Enamel Lamellae
28
Growth rings on enamel, inner layers newest, outer= oldest.
**longitudinal lines**
Striae of Retzius (line of Retzius)
29
What is this?
Mineralization of enamel.
Newest inside.
30
Lable red and yellow arrows
Yellow= line of Retzius
Red= Hunter schrieder bands
31
Fine, transverse wavelike grooves believed to be **external manifestations of the striae of Retzius**.
* Horizontal continuous around toot, parallel to CEJ
Perikymata
32
What are the black arrows pointing to?
Perikymata
33
Enamel formed **without any rods or prism pattern**, found primarily in the **cervical region** of the tooth.
* 30 um thick
* heavily minerlaized
* circular depressions (concavities) which may contribute to plaque adherence in young individuals
* Wear with age
| neck of tooth
Prismless enamel
34
What are 2 blue arrows?
* Regular enamel rods
* Prismless enamel
35
The **junction between enamel and dentin** is established as these two hard tissues begin to form and is seen as a scalloped profile in cross section
Dentinoenamel Junction
36
Odontoblast processes from within dentin hollow tubule that extend into the enamel
Enamel Spindles
37
Lable all 5 from top to bottom
1. Enamel
2. Enamel tufts
3. Enamel Spindle
4. Dentin
5. Dentin tubules
38
What is top blue arrow pointing too?
Enamel Tufts
39
What are long lines
Enamel Lamelle
40
A more **FLEXIBLE substance**
STRONG and RESILIENT: **increases fracture toughness** of enamel.
Dentin
41
Compare enamel and dentin
**Enamel=** hard + brittle
**Dentin=** Flexible + strong
42
What is dentin embryonically derived from?
**ECTOMESENCHYME**
* (Ectoderm) in origin (specialized connective tissues)
* Formed from the dental papilla of the tooth bud
43
What cells form the dentin?
Ondontoblast; dentinogenisis
44
Lable
* 1, enamel;
* 1a, gnarled enamel;
* 2, dentin;
* 3a, pulp chamber
* 3b, pulp horn
* 3c, pulp canal
* 4, apical foramen
* 5, cementum
* 6, periodontal fibers in periodontal ligament
* 7, alveolar bone
* 8, maxillary sinus
* 9, mucosa
* 10, submucosa
* 11, blood vessels
* 12, gingiva
* 13, striae of Retzius.
45
# Functions of the dentin-pulp complex
Formative/developmental
Production of primary and secondary dentin by **odontoblasts**.
46
# Functions of the dentin-pulp complex
Nutritive
Supplies nutrients and moisture to dentin.
47
# Functions of the dentin-pulp complex
Sensory/reparative
* Provides nerve fibers within the pulp to **mediate the sensation of pain.**
* Pulp **does not differentiate** between heat, touch, pressure, or chemicals.
48
# Functions of the dentin-pulp complex
Defensive/reparative
* Response to irritation via inflammatory reaction
* Deposition of reparative (by odontoblasts) dentin to act as a protective barrier
49
What do black teeth signify?
Reperative Dentin
50
What is sharp shooting, throbbing pain in a tooth related to?
Nerve related pain
| which is a protective mechanims
51
long, slender cytoplasmic cell processes of odontoblasts.
Tomes Fibers inside Dentin Tubules
52
What cells from enamel via what process
Amenoblast; via amenogensis
53
**small canals** that extend through the entire width of dentin, **from the pulp to the DEJ or CDJ**.
Dentin Tubules
54
**Lining within dentin** that is **much more mineralized** than the surrounding intertubular dentin.
peri-tubular dentin
55
Deitin amongst each dentin tubules
intertubular dentin
56
What cells run thrrough dentin tubuules
Tomes fibers from odontoblasts
57
Is dentin cellular or acellular?
**Cellular**, considered living tissue that can **respond to stimuli**.
58
59
odontoblastic processes that cross the DEJ into enamel.
Enamel Spindles
60
What is seening in this picture pointed out by the arrows?
Enamel Spindles
60
61
What is seen in this picuture?
Dentin Tubules
62
Explain the trend in tubules size throughout the dentin
* Smaller near the DEJ (more mineralized)
* Larger as you go deeper towards dental pulp
* Tubules in **superficial root dentin** are **smalller + less numerous** than those in** comparable depths of coronal dentin.**
63
* Form the dentin and maintain it.
* Cell bodies are **aligned along the inner aspect** of the dentin and form the **periphery of the dental pulp.**
* Cytoplasmic extensions found in dentinal tubules.
Odontoblast
64
If you can see a layer of amenoblasts what does this signify?
Tooth has not erupted yet, once it erupts the amenoblast layer dies off and canot be seen anymore.
65
What is A int his photo?
Odontoblasts
66
Explain the structure of dentin
* Bone like
* Hollow tubes
* Mineral nanoparticles (carbonated hydroxyapatite or **cHAP**) embedded in an **organic matrix of collagen protein fibers, and water**
67
Dentin is first deposited as a layer of **unmineralized matrix** called
Pre-dentin
| Innermost
68
What is the thickness of **pre-dentin**, what makes uo the majority of it, and where does it lie?
* 10-50um
* Collagen is principle content
* Lies in innermost portion of dentin
69
How does predentin evolves over development?
* Gradually **mineralizes into dentin** via noncollagenous matrix protiens being incorporated.
* THickness **remain constant** over dentinogenisis and **then deminishes with age**.
70
Explain left vs right
* Left= errupted tooth
* Right= unerupted tooth because you can see layer of epithelial tissue + layer of ameloblast that has not died off
71
Explain content of mature dentin?
* 70 is inorganic Material
* 20% organic materia (majority Collage 1)
* 10% water
72
What do each arrow point at
73
When does dentin formation begin?
**Immediatley before enamel formation.**
* Odontoblast geentrate extracellular collagen matrix and move away from adj ameloblasts (further into tooth)
74
Where is the most recently formed layer of dentin?
**Unmineralized zone of dentin** is immediately **next to the cell bodies of odontoblasts**
**Pre-dentin; Always on the pulpal surface**
* Most inner layer
* Older by DEJ
75
The dentin forming the initial shape of the tooth is called
primary dentin
* Forms intial shape of tooth
* Complete 3 years post toothe eruption
76
What is it?
Pre-detnin.
By cell bodies of odontoblast
77
when you see a buch of cells with blood vessles what is it?
Dental Pulp
78
Look
Look
79
What forms the majority bulk of the tooth?
Dentin
80
What affects the color of the tooth and why?
* **Dentin **determins color becuase it is underlyign the **translucent emame**l.
* The **color of dentin that shines throug**h is the color of the tooth.
81
How do you shade match
Shade match to dentin, more opaque crown colors block out the underlying dentin.
82
Physical and Mechanical Properties of Dentin
* Elastic= provides flexibility to tooth to prevent fractures
* Can withstand forces up to 300MPa
* Mineral nanoproducts protect collagen in dentin
83
What are the 2 dentinal junctions?
* DEJ; dentino-enamel juction
* CDJ; cemento-enamel junction
84
develops after **root formation has been completed** and represents the continuing, but much **slower**, deposition of dentin by odontoblasts.
Secondary Dentin
85
deposition of secondary dentin on the roof and floor of the chamber is greater, leading to an **asymmetrical reduction in the chamber’s size and shape**
Pulp Recession
| Gets narrower with age
86
What feature of secondary detnin helps protect the pulp?
The **tubules scleros** (fill with calified matierial) redily. Helps **reduce permeability of dentin**, protects pulp.
87
referred to as **reactive or reparative dentin** is produced in **reaction to various stimuli**, such as attrition, caries, or a restorative dental procedure.
*Fast, unorganized, dark color*
Tertiary Dentin
88
What distinguishes tertiary dentin
produced **only by those cells** directly **affected by the stimulus**.
89
What are the 2 subclasses of tertiary dentin?
1. Reactionary Dentin
2. Reperative Dentin
| Visibly cant tell diffrence
90
# What kind of tertiary dentin
deposited by preexisting odontoblasts.
Reactionary Dentin
91
# What kind of tertiary dentin
deposited by newly differentiated odontoblast-like cells.
Reperative Dentin
| messy!
92
Look
93
*Dentin that forms at a later stage* Requires **proliferation of epithelial cells** (HERTWIG’S epithelial root sheath)
Root Dentin
94
* These cells are from the **cervical loop** of the enamel organ.
* Initiate **differentiation of root odontoblasts**
HERTWIG’S epithelial root sheath
| Epitheliali Cells
95
What starts first root dentin formation or tooth eruption?
Root formation precedes!
96
WHat is signified by an x-ray showing a tooth with 2/3rd root formed?
tooth is going to erupt!
97
Look
Look
98
* Cells from the **fragmented root sheath**
* Form **discreet masses** surrounded by a basal lamina
* Persist in the **mature PDLs**
* May participate in **maintenance and regeneration** of periodontal tissues.
Epithelial (cell) rests of Malassez
99
Dental pulp is lined by what?
Lined by a layer of odontoblast from dentin
100
What are the 2 types of dental pulp?
1. Coronal pulp (up by the crown)
2. Radicular pulp (inside root)
Contain nerves, arterioles, venules, capillaries, lymph, tussues, cells etc.
101
How does dental pulp compare in young idv vs old
Young= wide large dental pulp
Older= thin narrow chambers
102
Thin layer of hard dental tissue covering the anatomic roots.
Cementum
103
What cells from cementum? ANd where?
**Cementoblast from mesehncymal cells** of the dental follicle
104
Is cementum softer or harder than dentin?
Softer, 50% hydrooxyapotitit, 50% organic matter/water
105
portions of the **PDLs embedded in cementum** and**alveolar bone** to attach the tooth to the alveolus.
Sharpeys Fibers
106
Is cementum vascular or avascular?
| It is living tissue
Avascular, no blood vessels.
107
Explain Acellular Cementum
* Layer with no cells
* Mostly in the coronal half of root (top)
108
Explain Cellular Cementum
* Has cells
* Mostly on apical half of root (bottom)
109
defined as the bodily movement of a tooth from its site of development to its functional position in the oral cavity
Active Eruption
110
is the apparent lengthening of the crown due to the loss of attachment, or recession of the gingiva.
Passive Eruption
111
During passive eurption what happens to the clinical crown and root?
Clinical crown getting longer, its not true eruption
112
# What junction
Relatively smooth
Attachment of **cementum to dentin** is firm
Cementodentinal Juction CDJ
| Not visible
113
**The joint between enamel and cementum**
* In about 10% of teeth, enamel and cementum DO NOT meet.
* Result in sensitive area
Cementoenamel Junction (CEJ)
114
Abrasion, erosion, caries, scaling, and restoration finishing, and polishing procedures can denude dentin of its cementum covering.
Causing what?
Dentin sensitivity (heat, cold, sweet, sour)
115
Cementum can repair itself and is not resorbed during normal conditions BUT when can resobtion occur?
* Excessisve pressure due to trauma or orthodontic movement.
* Apical resorbtion of cementum
