Enamel, Dentin, and Pulp Flashcards
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.
Enamel
Why is enamel so hard
Withstand large masticatory forces (complex organization of matrix)
Withstand acids (mineralization)
Explain thickness of enamel at diffent parts of tooth
- Thickest on coronal surface of crown
- Tapers in thicknest down to the CEJ
What is the thickness of enamel in the incsical ridge of incisors?
2mm
What is the thickness of enamel in the Cusp of pre-molar?
2.3-2.5mm
What is the thickness of enamel in the Cusp of molar?
2.5-3mm
How does the enamel of posterior teeth develope?
Cusps of posterior teeth begin as separate ossification centers, which form lobes that coalesce.
What is the mineralization and matrix of the enamel (3 things)
- Hydroxyapatite= 90-92%
- Organic matrix proteins = 1- 2%
- Water = 4- 12%
When conducting a filling, how much do you cut?
MUST cut past the enamel so that the material can adhere to the dentin.
The enamel is cellular or acellular?
Acellular it CANNOT be regenerated
The enamel is composed (structurally) of what 3 main things?
1.Enamel Rods
2. Enamel interods
3. Rod Sheaths
The tennis racket like structure that make up the enamel
Enamel rod
ROunded = stronger than square
Explain the postioning of the head and tail of the enamel rod.
Rounded Head= more incisal occlusally
Tail= more cervicall
The sturctures filling the gaps in bewteen enamel rods
Enamel Interrods
What are these?
Enamel rods and minerals within.
What are the two arrows pointing at?
- Enamel Rod
- Interod
Where does eache enamel rod extend from to where?
From DEJ to exterenal surface of teeth.
* Perpendicular from DEJ , **except in cervical region of permanent teeth cause theyre vertical **
Explain trend in enamal rod thickness
- At DEJ 4um
- At outer surface 8um
thicker on outer surface
Groups of enamel rods entwine with adjacent groups of rods, following a curving irregular path toward tooth surface.
Gnarled Enamel
Label
- 1= enamel
- 1a= gnarled enamel
- 2= dentin
- 3= dental pulp
- 12= gingiva
Changes in direction of enamel prisms produce an optical appearance called
waves in enamel
Hunter-Schreger bands
WHat is this?
Hunter-Schreger bands
- 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
Enamel Tufts
What is arrow pointing at?
Enamel Tufts
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
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
Growth rings on enamel, inner layers newest, outer= oldest.
longitudinal lines
Striae of Retzius (line of Retzius)
What is this?
Mineralization of enamel.
Newest inside.
Lable red and yellow arrows
Yellow= line of Retzius
Red= Hunter schrieder bands
Fine, transverse wavelike grooves believed to be external manifestations of the striae of Retzius.
* Horizontal continuous around toot, parallel to CEJ
Perikymata
What are the black arrows pointing to?
Perikymata
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
What are 2 blue arrows?
- Regular enamel rods
- Prismless enamel
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
Odontoblast processes from within dentin hollow tubule that extend into the enamel
Enamel Spindles
Lable all 5 from top to bottom
- Enamel
- Enamel tufts
- Enamel Spindle
- Dentin
- Dentin tubules
What is top blue arrow pointing too?
Enamel Tufts
What are long lines
Enamel Lamelle
A more FLEXIBLE substance
STRONG and RESILIENT: increases fracture toughness of enamel.
Dentin
Compare enamel and dentin
Enamel= hard + brittle
Dentin= Flexible + strong
What is dentin embryonically derived from?
ECTOMESENCHYME
* (Ectoderm) in origin (specialized connective tissues)
* Formed from the dental papilla of the tooth bud
What cells form the dentin?
Ondontoblast; dentinogenisis
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.
Functions of the dentin-pulp complex
Formative/developmental
Production of primary and secondary dentin by odontoblasts.
Functions of the dentin-pulp complex
Nutritive
Supplies nutrients and moisture to dentin.
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.
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
What do black teeth signify?
Reperative Dentin
What is sharp shooting, throbbing pain in a tooth related to?
Nerve related pain
which is a protective mechanims
long, slender cytoplasmic cell processes of odontoblasts.
Tomes Fibers inside Dentin Tubules
What cells from enamel via what process
Amenoblast; via amenogensis
small canals that extend through the entire width of dentin, from the pulp to the DEJ or CDJ.
Dentin Tubules
Lining within dentin that is much more mineralized than the surrounding intertubular dentin.
peri-tubular dentin
Deitin amongst each dentin tubules
intertubular dentin
What cells run thrrough dentin tubuules
Tomes fibers from odontoblasts
Is dentin cellular or acellular?
Cellular, considered living tissue that can respond to stimuli.
odontoblastic processes that cross the DEJ into enamel.
Enamel Spindles
What is seening in this picture pointed out by the arrows?
Enamel Spindles
What is seen in this picuture?
Dentin Tubules
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.**
- 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
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.
What is A int his photo?
Odontoblasts
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
Dentin is first deposited as a layer of unmineralized matrix called
Pre-dentin
Innermost
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
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.
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
Explain content of mature dentin?
- 70 is inorganic Material
- 20% organic materia (majority Collage 1)
- 10% water
What do each arrow point at
When does dentin formation begin?
Immediatley before enamel formation.
* Odontoblast geentrate extracellular collagen matrix and move away from adj ameloblasts (further into tooth)
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
The dentin forming the initial shape of the tooth is called
primary dentin
* Forms intial shape of tooth
* Complete 3 years post toothe eruption
What is it?
Pre-detnin.
By cell bodies of odontoblast
when you see a buch of cells with blood vessles what is it?
Dental Pulp
Look
Look
What forms the majority bulk of the tooth?
Dentin
What affects the color of the tooth and why?
- **Dentin **determins color becuase it is underlyign the translucent emamel.
- The color of dentin that shines through is the color of the tooth.
How do you shade match
Shade match to dentin, more opaque crown colors block out the underlying dentin.
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
What are the 2 dentinal junctions?
- DEJ; dentino-enamel juction
- CDJ; cemento-enamel junction
develops after root formation has been completed and represents the continuing, but much slower, deposition of dentin by odontoblasts.
Secondary Dentin
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
What feature of secondary detnin helps protect the pulp?
The tubules scleros (fill with calified matierial) redily. Helps reduce permeability of dentin, protects pulp.
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
What distinguishes tertiary dentin
produced only by those cells directly affected by the stimulus.
What are the 2 subclasses of tertiary dentin?
- Reactionary Dentin
- Reperative Dentin
Visibly cant tell diffrence
What kind of tertiary dentin
deposited by preexisting odontoblasts.
Reactionary Dentin
What kind of tertiary dentin
deposited by newly differentiated odontoblast-like cells.
Reperative Dentin
messy!
Look
Dentin that forms at a later stage Requires proliferation of epithelial cells (HERTWIG’S epithelial root sheath)
Root Dentin
- These cells are from the cervical loop of the enamel organ.
- Initiate differentiation of root odontoblasts
HERTWIG’S epithelial root sheath
Epitheliali Cells
What starts first root dentin formation or tooth eruption?
Root formation precedes!
WHat is signified by an x-ray showing a tooth with 2/3rd root formed?
tooth is going to erupt!
Look
Look
- 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
Dental pulp is lined by what?
Lined by a layer of odontoblast from dentin
What are the 2 types of dental pulp?
- Coronal pulp (up by the crown)
- Radicular pulp (inside root)
Contain nerves, arterioles, venules, capillaries, lymph, tussues, cells etc.
How does dental pulp compare in young idv vs old
Young= wide large dental pulp
Older= thin narrow chambers
Thin layer of hard dental tissue covering the anatomic roots.
Cementum
What cells from cementum? ANd where?
Cementoblast from mesehncymal cells of the dental follicle
Is cementum softer or harder than dentin?
Softer, 50% hydrooxyapotitit, 50% organic matter/water
portions of the PDLs embedded in cementum andalveolar bone to attach the tooth to the alveolus.
Sharpeys Fibers
Is cementum vascular or avascular?
It is living tissue
Avascular, no blood vessels.
Explain Acellular Cementum
- Layer with no cells
- Mostly in the coronal half of root (top)
Explain Cellular Cementum
- Has cells
- Mostly on apical half of root (bottom)
defined as the bodily movement of a tooth from its site of development to its functional position in the oral cavity
Active Eruption
is the apparent lengthening of the crown due to the loss of attachment, or recession of the gingiva.
Passive Eruption
During passive eurption what happens to the clinical crown and root?
Clinical crown getting longer, its not true eruption
What junction
Relatively smooth
Attachment of cementum to dentin is firm
Cementodentinal Juction CDJ
Not visible
The joint between enamel and cementum
* In about 10% of teeth, enamel and cementum DO NOT meet.
* Result in sensitive area
Cementoenamel Junction (CEJ)
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)
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
