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Operative, exam 1 > Histology > Flashcards

Histology Flashcards

1
Q

bud stage

A
  • initiation
  • 1st epithelial incursion into the ectomesenchyme of the jaw; the supporting ectomesencyhmal cells are closely packed beneath and around the epithelial bud
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2
Q

cap stage

A
  • proliferation
  • bud proliferates more into ectomesenchyme
  • epthithelial ingrowth looks like cap on ball of condensed ectomesenchyme
  • ingrowth = dental organ — later forms enamel
  • stage when blood vessels enter papilla (pulp)
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3
Q

bell stage

A
  • histodifferentiation and morphodifferentiation
  • dental organ comes to resemble a bell as undersurface of the epithelial cap deepens
  • phase when crown size/shape is determined
  • phase when specific cell tissue types develop
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4
Q

dental organ

A

forms enamel

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5
Q

dental papilla

A

forms dentin and pulp

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6
Q

dental follicle

A
  • condensed ectomesenchyme that gives rise to supporting tooth structures – cementoblasts adn PDL
  • limits dental papilla & encapsulates dental organ
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7
Q

late bell stage

A

dental lamina disintegrates

tooth now develops divorced from epithelium

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8
Q

enamel organ formation

A

occurs in cap to bell stages up til dentin formation

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9
Q

crown stage

A

hard tissue is laid down

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10
Q

changes from normal tooth devo??

A

cause extra or missing teeth

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11
Q

ameloblasts from what germ layer

A

ectoderm. so enamel is from ectoderm (dentin is mesoderm)

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12
Q

thickness of enamel

A
  • thickest at incisal/occlusal surfaces and thinnest toward CEJ
  • 2mm incisal edge incisors
  • 2.3-2.5mm PM cusps
  • 2.5-3.0mm molar cusps
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13
Q

enamel thickness at jxn of devo features

A

decreases (at cuspal lobes) – non coalesced lobes have fissured jxn and zero enamel — PITS and FISSURES

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14
Q

pits and fissures

A

pit – at deepest part of fossa

fissure – in grooves

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15
Q

enamel hardess surface vs DEJ

A

hardest on surface, least hard at DEJ

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16
Q

how hard is enamel

A

5x harder than dentin, like steel

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17
Q

enamel high elastic modulus and low tensile strength

A
  • stiff, does not deform under stress

- brittle, does not take much tensile strength to break

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18
Q

enamel composition

A

by volume…. 90-92% HA; 1-2% organic matrix proteins; 4-12% H2O

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19
Q

enamel structure

A

millions key hole shaped rods with HA crystals running at different angles; rods go from DEJ to surface and are densely packed and intertwined; rods are perpendicular to DEJ adn surface EXCEPT slightly apical at cervical region of tooth

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20
Q

where are enamel rods not perpindicular

A

cervical region of tooth – slightly apical

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21
Q

striae of retzius

A

growth rings, resulting variations in structure and mineralization due to rod formation process — rods are formed lineraly by successive apposition of enamel in discrete increments

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22
Q

imbrication lines of pickerell

A

when straie of retzius circles (As viewed from horiz.section) are incomplete at enamel surface, these grooves form

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23
Q

perikymata

A

elevation between the grooves called imbrication lines of pickerell that are due to incomplete circles of retizus striae; they are continuous around a tooth and parallel to CEJ and to each other

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24
Q

rods and susceptibility to acid

A

rods are made of millions of small elongated apatite crystallites; the orientation of crystallites influences susceptibility to acid

  • more dissolution in head region, where crystallites are almost parallel to rod long axis
  • less in tail region where they incline with increasing angles to the prism axis
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25
Q

is the DEJ hypermineralized

A

yes.

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26
Q

enamel lamellae

A

thin, leaf like faults between enamel rod groups that extend from enamel surface to DEJ, sometimes into dentin

  • -mostly organic material
  • -WEAK area that predisposes tooth to entry of bacteria and caries
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27
Q

enamel tufts

A

hypOmineralized structures that project between adjacent groups of enamel rods from DEJ; arise in dentin and extend into enamel; can play role in caries spread

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28
Q

enamel spindles

A

odontoblastic processes whose ends are thickened; they cross DEJ into enamel; may serve as pain receptors, which explains enamel sensitivity experienced by some patients during tooth prep

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29
Q

what explains enamel sensitivity experienced by some patients during tooth prep

A

enamel spindles; odontoblast processes with thick ends that extend into enamel

30
Q

histological structure of enamel rods — acid etching

A
  • mineral acids (phosphoric) selectively etch enamel rods
  • 25-75micrometer holes surrounded by interprismatic substances, which increases surface area by 200x
  • pores used to grip and retain composite resin tags

**acid opens spaces between rods, this allows resin monomers to permeate between crystals

31
Q

where are fractures more likely in relation to enamel rods

A

in planes parallel to rods because bond btwn rods is weak; less likely in plane across rods

32
Q

dentin support of enamel

A

prevents fractures, undermining is loss of dentinal support

rods are perpindicular to DEJ and surface

inner end of enamel rod must be on DEJ, not just air

33
Q

enamel color

A

translucent, color comes from dentin

localized discoloration from devo issues

34
Q

enamel repair

A

–only self repair is partial remineralization by F- ions

35
Q

enamel transport

A
  • enamel is permeable to certain ions/molecules
  • route of passage through HYPOmineralized structural units (which are rich in organic material) – rod sheaths, enamel cracks and other defects
  • H2O is transporting medium through small intercrystalline spaces
  • H2O2 (bleaching agent) has low molecular weight, so it easily passes through enamel adn dentin
36
Q

bleaching teeth

A
  • lighten teeth by chemical agent that oxidizes the organic pigmentation of teeth
  • H2O2 is a bleaching agent that easily passes through enamel adn dentin because low molec.wt
37
Q

dentin origin

A

mesoderm

38
Q

dentin composition by volume and weight

A

by volume: 45%mineral, 33%organic, 22%H2O

by weight: 70%mineral, 20%organic, 10%H2O

39
Q

dentin fxn

A 
protect pulp (barrier to chemical/thermal insults)
support enamel

**thickness of the remaining dentin following a cavity prep is the MOST IMPORTANT factor in protection of pulp and contributes to success/failure of restoration

40
Q

what is most important factor in protection of pulp following cavity prep

A

thickness of remaining dentin

41
Q

characteristics of dentin – thickness, compressibility, resiliency, etc

A
  • elastic
  • 1/5th as hard as enamel
  • flexibility — helps support more brittle/nonresilient enamel
  • 3x harder at DEJ than pulp
  • slight compressibility adn resiliency, counteracts brittle enamel
42
Q

radiograph dentin vs enamel

A

dentin is more radiolucent (darker)

43
Q

basic devo of dentin

A
  • odontoblasts form dentin
  • cell bodies are in pulp and the processes go up in dentin tubules
  • dentin is series of S-shape tubules from pulp to DEJ
  • predentin = unmineralized area lined by odontoblast cell bodies right agsint pulp
44
Q

predentin

A

between pulp and dentin there is an unmineralized zone of dentin smack up against cell bodies of odontoblasts

45
Q

where is dentin most dense adn tubules largest

A
  • lumens are widest at PULP and most numerous adn dense at pulp
  • closer to DEJ = smaller and more sparsely distributed tubules
  • comparing similar depths btwn crown adn root dentin – more tubules in coronal dentin
46
Q

types of dentin

A
  1. intertubular = primary product of odontoblasts, bwtn tubes
  2. intratubular = lines the tubes, more mineralized
  • -primary: forms initial shape of tooth
  • -secondary: forms at reduced rate throughout life
  • -tertiary = reparative: forms when stimulated to increase distance between pulp adn stimulus
47
Q

intertubular dentin

A
  • primary secretory product of odontoblasts
  • type I collagen fibrils aligned at right angles to tubule
  • apatite crystals oriented parallel to collagen fibrils
  • crystals = .1 micrometer long
48
Q

intratubular = peritubular dentin

A

lines tubules adn more mineralized than intertubular

49
Q

reparative dentin

A

tertiary. formed in response to moderate level stimuli (attrition, caries, some op.procedures); structurally different from primary and secondary; increases distance between pulp and stimulus; some liners and pulp capping procedures used to stimulate tertiary dentin for protection

50
Q

fluid movement adn dentin

A

fluid movement (such as cutting or air drying) distorts odontoblasts and afferent nerves adn causes pain

51
Q

microscopic pulp exposures

A
  • from any preps that have floor in dentin
  • because dentinal tubules extend to pulp
  • use cavity liners and bases to protect/seal cut dentinal tubules
52
Q

smear layer

A
  • thin layer of debris on surface when dentin is cut/abraded

- composed of HA adn altered/denatured collagen

53
Q

smear plug

A

when smear layer fills opening of dentin tubules

smear plugs make dentin tubules 90% less permeable

54
Q

micromechanical bonding to dentin

A

similar to enamel; adhesion relies primarily on penetration of adhesive monomers into the network of collagen fibers left exposed by acid etching

55
Q

chemical bonding of dentin

A

important for adhesive materials that do not require etching; glass ionomer cements & phosphate based self etch adhesives
– bonds between HA + either polycarboxylic monomers or phosphate monomers

56
Q

3 step etch and rinse bonding

A
  1. etchant: removes smear layer, exposes collagen, opens tubules, decreases surface free energy
  2. primer: binfunctional molecules (h.phobic and h.philic); envelops external surface of collagen fibrils and increase surface free energy til compatible with h.phobic molecules
  3. bonding agent: mainly h.phobic monomers; penetrate adn polymerize in interfibrillar spaces; structural backbone of hybrid layer
57
Q

dentin etching – role of acids

A
  • partially or totally remove smear layer and demineralize dentin
  • open tubules and expose dense filigree of collagen fibers
  • increase microporosity of intertubular dentin
58
Q

how much is dentin demineralized from etching

A

up to 7.5micrometers

depends on type and concentration of acid and time it is applied

59
Q

hybrid zone

A

primer and bonding agent appleid to etched dentin; they penetrate intertubular dentin and form HYBRID zone (resin-dentin interdiffusion zone)

60
Q

dental pulp

A
  • dentin all around it, immediatly lined by odontoblast cell bodies
  • contains: nerves, arterioles, capillaries, lymph channels, conn.tissue cells, intercellular substance, odontoblasts, fibroblasts, macrophages, collagen and fine fibers
61
Q

4 fxns of dental pulp

A
  1. nutritive (supplies odontoblasts and processes)
  2. formative/devo (primary dentin)
  3. protective/sensory (pain sensation from nerves)
  4. repair/defense (tertiary dentin)
62
Q

pulp chamber size

A

decreases over life because secondary adn tertiary dentin make it smaller

63
Q

cementum

A
  • avascular, thin, bony tissue lining dentin of root
  • fxn = attachment of supportive fibers of PDL
  • cementoblasts (MESENCHYMAL CELL origin)
  • 45-50% HA by weight, softer than dentin
  • lighter yellow than dentin
  • formed throughout life to replace itself as it wears so attachment is intact
64
Q

sharpey’s fibers

A

portions of pincipal collagenous fibers of PDL embedded in cementum and alveolar bone to attach tooth

65
Q

2 types cementum

A
  1. acellular: living tissue that does not incorporate cells into structure — CORONAL
  2. cellular: APICAL
66
Q

cementum at apical part of root

A

surrounds apical foramen and can extend into inner pulp canal

67
Q

cementum adn enamel meet, 3 ways

A
  1. overlap
  2. meet
  3. space bewteen cementum and enamel – SENSITIVE area
68
Q

cementum composition by weight

A

45-50% inorganic HA and 50-55% organic adn water

69
Q

resorption of cementum

A

not normal, but can happen if excessive ortho pressure

70
Q

gingiva

A
  • protective, easily damaged by operative instruments
  • poor restoration contours and morphology –> long term perio issues
  • incorporate the following into restoration design: embarsure form, contact area, contours, ht of contours

Operative, exam 1 (6 decks)

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