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Human Anatomy > Oral Histology > Flashcards

Oral Histology Flashcards

1
Q

tooth germ

A
  • enamel organ
  • dental papilla
  • dental sac (forms periodontal ligament, alveolar bone and cementum)
    give rise to tooth and supporting tissue (dental sac)
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2
Q

enamel characteristics

A
  • hardest mineralized tissue in body
  • nonvital – acellular, avascular, lack of nerve
  • inorganic mostly –> 96%
  • organ + water –> 4%
  • lacks collagenous proteins (no collagen)
  • “piece of dead tissue”
  • once enamel is complete ameloblasts will be gone –> this is why enamel cannot be regenerated
  • yellowish white color (translucent)
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3
Q

enamel

A
  • enamel rods = enamel prisms
  • interrod enamel = interprismatic substance
  • located in between enamel rods
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4
Q

enamel rod

A
  • enamel prisms
  • “keyhole” shape consisting of a head and tails
  • the head of the keyhole shape
  • basic morphologic/structural unit of enamel
  • bound together by an interprismatic substance (interrod enamel)
  • each is formed by increments by a single secretory ameloblast with Tomes’ process
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5
Q

interrod enamel

A

the tail of the keyhole shape
- cylindrical rods embedded in interrod enamel

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6
Q

similarities of enamel rod and interrod enamel

A

both are made of enamel crystals

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7
Q

difference between enamel rod and interrod enamel

A
  • rod: crystals oriented parallel to rod axis; primarily along central axis
  • interrod: crystals oriented at angle to rod
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8
Q

how many ameloblasts participate in the formation of one classical enamel rod

A

four

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9
Q

enamel rod orientation

A
  • extend approximately from DEJ to enamel surface
  • perpendicular to DEJ and enamel suface, but slightly S-shaped in both horizontal and vertical planes
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10
Q

interrod orientation

A

crystals oriented at an angle to rod

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11
Q

enamel micro features

A
  1. DEJ
  2. cross striations
  3. lines (stria) of Retzius
  4. Hunter-Schreger bands
  5. gnarled enamel
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12
Q

DentinoEnamel Junction (DEJ)

microfeature of enamel

A
  • scalloped junction in section
  • convex surface faces dentin
  • prevents shear forces from separating enamel from dentin
  • first formed enamel and dentin located here
  • scalloped is only term used to describe DEJ
  • increases contact area between enamel in dentin
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13
Q

cross striations

enamel micro feature

A
  • daily incremental growth lines
  • run at angle to rod axis
  • space between successive cros striation is about 4 micrometers in human enamel
  • represent a layer of enamel deposited over a period of 24 hours
  • form a ladder like appearance
  • runs perpendicular to enamel rod –> are the cross striations
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14
Q

lines (striae) of Retzius

micro features of enamel

A
  • incremental growth lines
  • distance between successive striae represents a layer of enamel deposited over a period of 5 to 10 days
  • have increased organic content and are indicative of the rhythmic variation in the calcification of the enamel matrix
  • formed during the secretory phase of amelogenesis
  • retzius striae represent the spaces between a series of successively larger cones stacked one outside the other
  • lines of Retzius appear like tree rings in the cross section and are NOT parallel in longitudinal section
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15
Q

lines of Retzius cont’d.

A
  • accentuated by diseases and changes in nutriton
  • neonatal line: most accentuated Stria of Retzius
  • reflects physiologic changes occuring during birth
  • in all primary teeth and sometimes cusps of first permanent molars
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16
Q

lines of Retzius (cont’d.)

A
  • perikymata = imbrication lines
  • surface manifestations of lines of Retzius
  • horizontal shallow grooves on enamel surface
  • more prominent on the facial side of newly erupted teeth
  • usually lost through wear
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17
Q

Hunter-Schreger Bands

enamel microfeatures

A
  • represent alternating groups of cross-sectioned enamel rods and longitudinally sectioned enamel rods
  • extend only ~ 2/3 distance from DEJ toward enamel surface
  • can be found anywhere along DEJ
  • observed only with reflected light/scanning EM
  • appears as an alternating light and dark bands extending from DEJ toward the enamel surface in reflected light
  • dark bands correspond to cross-sectioned enamel rods
  • light bands represent longitudinally sectioned enamel rods

dark and light bands because they reflect light differently

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18
Q

gnarled enamel

A
  • represents groups of twisted enamel rods
  • DEJ –> enamel surface
  • can only be found at the cuspal and incisal areas
  • increases resistance of enamel to fracture to mastication stress
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19
Q

enamel demineralization

A
  • carbonated apatites in crystal core
  • carbonated apatite is more susceptible to acid demineralization than hydroxyapaptite and fluoroapatite
  • crystal ends first to dissolve, then along core
  • dissolves from inside out
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20
Q

enamel demineralization (cont’d.)

A
  • crystal vs their sides
  • crystals dissolve more readily at their ends than on their sides
  • thus crystals lying perpendicular to the enamel surface are more vulnerable
  • crystal orientation is different in enamel rod and interrod enamel
  • rod crystal ends are perpendicular to enamel surface
  • interrod crystal ends not exposed
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21
Q

enamel demineralization

A

acid etching
* technique to remove surface minerals of enamel with dental etchants
* result in differential etching of rod and interrod enamel
* provides better bonding surface due ot increased porosity of enamel surface
* important clinically for fissure sealants and bonding restorative materials to enamel

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22
Q

acid etching patterns

A
  1. Type 1 –> most common
    * preferential removal of rods
  2. Type 2
    * reverse of type 1 - interrod enamel removed
  3. Type 3
    * least frequent
    * irregular and indiscriminate pattern
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23
Q

age changes in enamel

A

attrition
* enamel is non-vital
* attrition of enamel may expose dentin
* pits and fissures may be eliminated
color
* darkness increases with age
* thinning of enamel
* extrinisic staining
permeability
* decrease with age
* decrease in pore size between crystals; crystals increase in size
water content
* decrease with age
* decrease pore size forces water out
nature of surface layer
* changes due to ionic exchange with oral environment
* fluoride ion most prevalent
brittleness: increase with age
decreased incidence of caries
* increase fluoride ion content
* loss of surface areas susceptible to caries
* change in diet

dental enamel cannot be regenerated

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24
Q

dentin characteristics

A
  • resilient support for enamel
  • inorganic - 68% (hydroxapatite crystals)
  • organic - 22% (primary type 1 collagen)
  • water - 10% by weight
  • forms throughout life of the tooth
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25
Q

dentinal structure (dentinal tubules)

A
  • tubular spaces w/in dentin and containing odontoblast processes and dentinal fluid
  • approx. 1 in 10 contain nerve fibers
  • extend from the DEJ to the dentin-predentin junction
  • S-shaped in crown; straight in root. Thus primary curvatures of the dentinal tubules is less in root than crown dentin
  • tapered contour: large diameter closer to pulp
  • canaliculi: connect adjacent tubules
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26
Q

dentinal structure (odonblast processes)

A
  • extend from cell body out into dentinal tubule
  • predentin does not have dentinal tubules
  • in mature dentin not all the way to DEJ/CDJ
  • have numerous side branches
  • adjacent cell processes contact via their side branches withing canaliculi (contain the side branches)
  • process tapers from cell body towards DEJ/DCJ

dentin covered by cementum

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27
Q

dentin structure (incremental lones of von Ebner)

A
  • daily incremental growth lines
  • distance between sucessive lines represents the amount of dentin deposited over a period of 24 hours
  • similar to cross striations in enamel
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28
Q

dentin structure (contour lines of owen)

A
  • wider thickened incremental lines
  • represent metabolic disturbance occuring during apposition
  • similar to stria of Retzius in enamel
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29
Q

dentin structural features (neonatal line)

A
  • accentuated contour line of Owen
  • represent sudden physiologica change occuring during parturition
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30
Q

classification of dentin

A

peritubular or intratubular dentin
* lines the wall of the dentinal tubule
* highly mineralized dentin
intertubular dentin
* all dentin located between dentinal tubules –> majority of dentin
* less mineralized than intratubular dentin

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31
Q

classification of dentin

A
  • mantle dentin
  • circumpulpal dentin
  • predentin
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32
Q

mantle dentin

A
  • 1st layer formed of crown and root dentin
  • nearest to DEJ/CDJ
  • collagen fibers larger and oriented perpendicular to DEJ
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33
Q

circumpulpal dentin

A
  • bulk of dentin underlying the mantle dentin
  • collagen fibers that are small in diameter and more randomly oriented
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34
Q

predentin

A
  • a layer of newly secreted organic matrix
  • unmineralized –> similar to osteoid bone
35
Q

classification of dentin

A
  • primary dentin
  • secondary dentin
  • tertiary dentin
36
Q

primary dentin

A

dentin formed prior to and during tooth eruption

37
Q

secondary dentin

A
  • dentin formed after the tooth is in occulsion
  • junction between 1 and 2ndary dentin characterized by sharp change in direction of dentinal tubule
  • forms more slowly than primary dentin and throughout life of toth
38
Q

tertiary dentin

A
  • localized rapid formation of dentin
  • deposited on pulpal surface under secondary dentin only at sites corresponding to areas of stimulation
  • response to some trauma which exposes dentinal tubules from pulp (trauma such as a cavity)
  • sparse and irregular dentinal tubules
39
Q

types of tertiary dentin

A
  • reactive dentin
  • reparative dentin
40
Q

reactive dentin

A
  • formed by preexisitng/original odontoblasts
  • newly formed tubules continuous with those of secondary dentin
41
Q

reparative dentin

A
  • formed by newly differentiated odontoblasts
  • preexisiting dentinal tubules discontinuous
42
Q

dead tract dentin

A
  • tract of dentin containing empty tubules
  • forms when odontoblasts either killed/injured and processes retracted, leaves empty dentinal tubules
  • acute response to some trauma
  • dentinal tubules are filled with air during histological processing
  • appears black under microscope
43
Q

what is a dead tract sealed off with?

A

tertiary dentin

44
Q

sclerotic dentin

A
  • area of dentin containing dentinal tubules completely occluded with minerals
  • slower response to chronic trauma
  • appears transparent uner microscope
45
Q

dentin sensitivity

A
  • extreme sensitivity of pulp-dentin complex is unusual and difficult to explain
  • mechanical, thermal, and tactile stimuli to the dentin are perceived as pain
  • products like bradykinin and histamines which produce pain in other tissues but not in dentin
46
Q

3 theories for dentin sensitivity

A
  • nerves in dentin
  • 1 in 10 tubules contains a free nerve ending
  • odontoblast as receptor
  • nerves shown to synapse on odontoblast cell body
  • hydrodynamic
  • fluid movement through tubule stimulates pulpal nerves
  • most plausible theory
47
Q

pulp

A
  • only soft tissue of the tooth
  • specialized loose CT
  • derived from neural crest cells
  • functions: formation, nutrition, defense, sensation, reparative
  • forms throughout life of tooth
48
Q

pulpal anatomy

A
  • pulp
  • coronal pulp: located in coronal pulp chamber and pulp horns
  • radicular pulp: located in root canals
  • apical foramen
  • where nerves, blood vessels, and lymphatic vessels enter and leave the tooth
  • accessory root canals
  • connection between main root canals and PDL
  • form during root development
49
Q

odontoblastic layer (pulp zone)

pulp histology

A
  • outermost layer against predentin
  • dentinal nerve fibers located between cells
50
Q

cell-free zone (of Weil)

pulp zone

A
  • not “cell free” just has fewer cells
  • capillary and nerve plexus
51
Q

cell rich zone

pulp histology

A
  • increased cell density - mainly fibroblasts
  • more extensive vascularity
52
Q

pulp core/central zone

pulp zone

A
  • central most region of pulp
  • numerous cell types, nerves and blood vessels and lymphatic vessels
53
Q

pulp cell types

A
  • fibroblasts - most
  • odontoblasts - next most
  • undifferentiated mesenchymal cells
  • macrophages
  • T- lymphocytes
54
Q

pulp stones

A

= denticles
* true pulp stones
* ectopic mass of dentin in pulp
* odontoblasts and dentinal tubules
* false pulp stones
* calcified mass in pulp
* concentric rings of lamellae
* location: free, attached or embedded

55
Q

age changes in pulp

A

fibrosis: fibroblast cell number decrease and collagen fiber increases
* pulp volume decreases due to secondary dentin, tertiary dentin, pulp stones

56
Q

periodontium

A

tissues that invest and support the tooth
* composed of cementum, alveolar process, periodontal ligament (PDL)

57
Q

cementum

A

mineralized CT covering root dentin

58
Q

cementum characteristics

A
  • avascular, non-innervated tissue
  • covers and protects root dentin
  • anchors PDL fibers to tooth root
  • forms throughout life of tooth to compensate for occulsal wear
59
Q

cementum chemical/physical characteristics

A
  • inorganic (mineral) - 45-50%
  • organic 50-55%
  • hardness less than dentin
60
Q

cementum cells

A

cementoblasts
* form cementum
* found on surface of cementoid

cementocytes

  • cell body situated in lacunae
  • cell processes lying in canaliculi, radiating out from cell body only toward PDL
61
Q

fiber (collagen type I) types

A
  • intrinsic fibers (IF)
  • produced by cementoblasts
  • run parallel to root surface
  • extrinsic fibers (EF)
  • produced by PDL fibroblasts
  • Sharpey’s fibers of PDL
  • run at right angles to the root surface
62
Q

cementum classification

A

based on the presence/absence of cementocytes and fiber types
* acellular extrinsic fiber cementum (AEFC)
* cellular intrinsic fiber cementum (CIFC)

63
Q

acellular extrinisic fiber cementum (AEFC)

A
  • primary cementum
  • no cementocytes
  • majority of fibers are extrinsic PDL collagen fibers
  • covers cervical ~2/3 of root
  • forms slowly during root eruption
  • plays a major role in tooth attachment
64
Q

cellular intrinsic fiber cementum (CIFC)

A
  • secondary cementum
  • contains cementocytes
  • majority of fibers are intrinsic fibers
  • covers ~1/3 of root
  • forms rapidly
  • plays a minor role in tooth attachment
65
Q

cementoenamel junction (CEJ)

A

3 patterns
* cementum ovelaps enamel ~ 60%
* cementum meets enamel end on 30%
* gap between cementum and enamel - 10%
* can occur developmentally or post eruptive –> ex: abrasive action of tooth brush
* exposed root dentin - dentin hypersensitivity

66
Q

clinical significance of cementum

A

orthodonic tooth movement
* cementum is more resistant to resorption than alveolar bone
* application of proper forces can move teeth through bone

67
Q

cementum anomaly

A

hypercementosis
* abnormal thickening of cellular cementum
* diffuse/circumscribed
* can affect entire dentition, single tooth or portions of one tooth
* tooth may become ankylosed

68
Q

alveolar process

A

those portions of the maxilla and mandible that support the roots of the teeth

69
Q

alveolar process characteristics

A

contains more mineral than cementum

70
Q

alveolar process components

A
  • alveolar bone proper
  • cribiform plate, bundle bone, lamina dura
  • cortical plate
  • inner plate: lingual and palatal surface
  • outer plate: buccal and labial surface
  • central spongiosa
  • trabecular bone
71
Q

alveolar bone proper - bundle bone

A

specialized type of compact bone because the ends of PDL fiber bundles insert into it

72
Q

alveolar bone proper

A
  • referred to as the lamina dura radiographically because it appears more radiopaque than the adjacent supporting bone
  • remodeling rate may be high due to constant adaptation to tooth movements
  • smooth surface in young, rough with age
  • NO periosteum present
73
Q

cortical plate

A
  • inner = lingual and palatal suface
  • outer = labial and buccal surface
  • alveolar crest: junction of cortical plate and alveolar bone proper
  • covered with a periosteum
74
Q

central spongiosa

A
  • trabecular (spongy/cancellous) bone supporting the alveolar bone proper and cortical plate
  • marrow: red (hemopoietic) in young, yellow in aged
75
Q

alveolar process: bony septa

A
  • interdental septum
  • bony septum situated between the roots of adjacent single-rooted/multirooted teeth
  • interradicular septum
  • bony septum located between roots of a single multirooted tooth
76
Q

edentulous jaws

A

lose alveolar process

77
Q

periodontal ligament (PDL)

A
  • a specialized soft CT with ligament cells and ECM
  • fibers: collagen fibers organized into groups –> principal fibers
  • blood and lymphatic vessels
  • nerves
78
Q

PDL ligament cells

A
  • fibroblasts
  • cementoblasts
  • osteoblasts
  • osteoclasts
  • odontoclasts
  • epithelial rests of Malassez: undifferentiated mesenchymal cells
79
Q

epithelial rests of malassez

A

remenants of Hertwig’s epithelial root sheat

80
Q

PDL principal fibers

A
  • fiber bundles that exit the cementum and alveolar bone proper to form the periodontal ligament
  • made of type I collagen
  • classification
  • dentoalveolar group - attachment of tooth to alveolar bone
  • gingival group - part of gingiva
81
Q

PDL dentoalveolar group

A
  1. alveolar crest
  2. horizontal
  3. oblique –> largest group
  4. apical
  5. interradicular –> extend from cementum of bifurcation to interradicular septum
82
Q

sharpey’s fibers

A
  • perforating fibers
  • portions of PDL fibers embedded in the alveolar bone proper/cementum
  • fiber bundles inserting in bone are much larger than those inserting in cementum
83
Q

interstitial spaces

A

spaces located between bundles of collagen fibers
* blood & lymphatic vessels and nerves

84
Q

tooth movements

A
  1. compression
    * on the side toward which tooth moves
    * resorption of alveolar bone
  2. tension
    * on the side opposite to compression
    * formation of alveolar bone

Human Anatomy (3 decks)

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