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da cursed tooth > WEEK FOUR ONWARDS > Flashcards

WEEK FOUR ONWARDS Flashcards

1
Q

Outline enamel general characteristics

A
  • hardest biologic tx in body - thickest over cusps/thinnest at cervical margin
  • composed of inorganic mineral, organic matter and water
  • white w/ low translucency that increases with age = reflects yellow colour of dentine
  • composed of keyhole shaped rods made by ameloblasts
  • thickest over cusps [2.5mm] and thinnest at cervical margin [knife edge]
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2
Q

outline chemical characteristics of enamel

A
  • by WEIGHT= 96% inorganic material -by weight 4% organic material + water

inorganic
- [crystalline calcium phosphate // hydroxyapatite - HA]
- mineral content ^ from DEJ to surface
- HA crystallites = hexagonal 70nm width and 25nm thick
much bigger than the crystallites in dentine, cementum and bone
- F levels decline from outer to inner layers

organic
- enamelin protein on and in between HA crystals [aids permeability]
- AAs, peptides, lipids

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3
Q

describe enamel prisms [rods] and the THREE types of cross sections

A

each rod filled w crystals
- those in head follow long axis of rod
- those in tail lie in cross axis to head [65-70d gradual divergence from head crystals]
- each rod = FOUR ameloblasts
-1 forms head, 2 form neck, 1 forms tail

  1. pattern I
    - parallel rows
  2. pattern II
    - keyhole pattern [most predominant]
    - occupies BULK of enamel
  3. pattern III
    - circular
    - near DEJ and surface
    - interprismatic areas exist between prisms

changes in crystal orientation throughout rod = changes in angle to enamel
- cervical margin = 90d
- occ/incisally = 60d
- fissues 20d

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4
Q

describe the keyhole pattern of enamel rods

A

-tail located between FOUR heads
- in head = crystals parallel to long axis
- in keyhole = crystals diverge in different directions from head central area
- in tail = crystals 65-70d from head crystals [gradual divergence]

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5
Q

describe the Hunter - Shreger Bands [HSB]

A

alternating light and dark bands which begin at DEJ and end before reaching enamel surface

due to alternating directs of prisms
- strengthen enamel and prevent cracks

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6
Q

define the incremental lines [stria of retzius] and describe the TWO types

A

due to rhythmic depo of enamel
- as enamel matrix mineralises it follows the pattern of matrix depo = provides growth lines

periods of activity alternates w period of acquiescene = resulting in incremental lines
1. short periods = cross striations [daily]
2. long period = enamel striae [~weekly]

cross striations
- rods alternating between thick.thin segments = cross striations
- lines at right angles w long axis of prisms
- 2.5-6um apart [2um at cervical enamel]
- 7-10 cros.stri between 2 striae

enamel striae
- lines running oblique across prisms in longitudinal sections
- straie’s ovelapping cusps do not reach surface
- due to metabolic distubrances during mineralisation [eg neonatal line]
- absent in enamel formed before birth

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7
Q

outline what perikymata grooves are

A

occur as enamel striae reach enamel surface –> series of fine grooves/ridges in circumferential pattern

close together near cervical margin

in prim teeth = only seen in cervical enamel of second molars

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8
Q

describe the dentin enamel junction, its TWO patterns and what structures as visible

A
  • reflects boundary between dentin and enamel
  • patterns = scalloped // smooth
  • scalloped = beneath cusps and incisal edges
    HIGH shearing forces
  • smooth = at lateral surface
  • LOW shearing force
  • at the DEJ: spindles, tufts and lamellae are visible
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9
Q

describe enamel spindles

A

tubules from dentin extending up to 25um –> enamel

believed to be odonotoblastic process that remained between ameloblasts

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10
Q

describe enamel tufts

A
  • junctional structures in inner third of enamel = resembles grass
  • travels in same direction as prisms but is several prisms wide
  • contains hypomineralised areas
  • suggested to travel from residual protein matrix
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11
Q

describe enamel lamellae

A
  • runs through entire thickness of enamel
  • appearance = sheet like structural defect
  • hypomineralised
  • caused by = imcomplete maturation of prism groups during development // cracks after eruption
  • contains enamel proteins
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12
Q

define what an enamel pearl is and its cause

A
  • enamel found where it is not meant to be [usually in the furcations of molar roots] - can ^ retention of biofilm = periodontal lesions
  • caused by failure of Hertwif epithelial root sheath to separate from dentin in development
  • prolonged contact induces odontogenic epithelium to secrete enamel
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13
Q

describe predentin layer

A

innermost layer of dentin - surrounding pulp [10-40um thickness]
- not mineralised yet
- sec by odontoblasts by golgi app. and mitochon.
- appears pale compared to mineralised dentin

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14
Q

describe translucent dentin

A

forms w ageing due to tubule occlusion by peritubular dentin [pronounced at root apex]
- used in foresic dentistry in age determination

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15
Q

describe sclerotic dentin

A

tubular occlusion caused by stimulus [appearance similar to translucent dentine but related to stimulus not age]
- tubules = completely obliterated [^ in amount w age] = pulp permeability eliminated in this case
- believed to be protective mechanism of pulp

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16
Q

describe dead tracts

A

when dentin damaged = odontoblastic process either dies or retracts = empty tracts [appears dark under light microscope]

with time the empty tubule can be completely filled w minerals

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17
Q

list THREE properties which prevent bacteria from invading dentine through tubules and describe the permeability of coronal dentin

TBCONT..

A

outward dentinal fluid contains immunoglobin

presence of intratubular deposits of mineral

presence of large collagen fibrils

18
Q

state the curvature of dentin tubules and describe the FIVE types of structural incremental lines in dentin

A

primary curvature = long sweeping s shape

secondary curvatures = along length of prim.curv. = gentle, wavy undulations = sec.curv

**Lines of Von Ebner
**- SHORT cross striations across tubules [reflect rhymic deposition]
- finer, more regular incremental lines representing daily deposition [less pronounced than contour lines of owen]

Andresen Lines
- LONG period lines
- 16-20 um apart
- associated w change in **collagen fibril orientation **
- more prominent that von ebner // less pronounced than contour lines of owen

Shreger Lines
- associated w peaks of PRIMARY sigmoid curvatures

**Contour Lines of Owen **
- associated w SECONDARY curvatures
- accentuated incr.growth lines = represent stress/ rate changes in dentin formation
- another type = neonatal lines [marks dentin formed before/after birth]

19
Q

define coronal, radicular, apical foramina and accessory canals of PULP

A

**coronal pulp **
- occupies crown of tooth with pulp horns [extend into cusps]
- larger than root pulp + different structure

**radicular pulp
**- extends from cervical regions to apex of tooth
- singular in ant teeth//multiple root pulps in post. teeth

apical foramina
- opening of root pulp –> periodontium

**acc. canals // lateral canals ** **
**- can result blood vessells obstructing dentin fotmation
- OR from break in epithelial root sheath
- occurs in 33% of perm teeth
- opens to PDL

20
Q

describe what happens to the root canal anatomy w age

A

large and open apex in immature tooth –> narrows w age

cases of multiple foramina is high –> ^ in complexity and prevalence in multi rooted teeth

21
Q

List and describe the FOUR functions of pulp

A
  1. inductive
    - interacts w oral epithelium to initiate tooth formation in early development
  2. formative
    - odontoblasts form dentine
  3. protective/defence
    - formation of reparative dentine, inflammatory response
  4. nutritive
    - carries O2 and nutrition –> tooth
    - comms w PDL via apical foramen and acc.canals
    - richly vascularised and innervated
22
Q

describe the pulp composition

A
  • appearance = loose CT
  • type 1 collagen fibres
  • ground substance, macromolecules and fluid

cells
- mesenchymal cells [potential fibroblasts, macrophages, odontoblasts]
- neurons [trigeminal afferents and sympathetics]
- transient cells
- endothelial cells [blood/lymph]
- LACKS ADIPOSE
- highly organised at periphery

23
Q

describe the histological organisation of the pulp

A

beneath predentin = odontogenic zone [pulpal layer]
from superficial –> deep

odontoblastic layer [outermost]
- odon. form single pseudostratified layer of cells attached to predentine surface [single cytoplasmic extensions –> dentinal tubules]

cell free zone [beneath odontoblast layer]
- nerve/ capillary plexus also located here
- not ENTIRELY cell free but much less than upper layer

cell rich zone
- high conc capillaries + axons
- fibroblasts + mesenchymal cells
- not as many cells as odontoblastic layer

central pulp // pulpal core
- bulk
- neurovascular core

24
Q

describe FOUR pulpal cell types

A
  1. odontoblasts
    - line perimenter of pulp from time they begin organise to form dentin –> when quiescent/ no longer producing dentin at rapid rate
  2. fibroblasts
    - protein producing cell - become smaller w age
    - most numerous as they’re located throughout pulp
    - in young pulp = produce collagen fibres and ground substance
  3. shwann cells
    - form myeline sheath of nerves
    - associated w ALL PULP NERVES
  4. endothelial cells
    - line capillaries, veins and arteries of pulp
25
Q

explain the pulpodentine complex and the effect of restorative procedures

A
  • exposed fluid filled dentin tubules allow minute [small] shift across dentine in tactile, thermal, osmotic or evaporative stimuli
  • fluid shift stims odontoblasts, pulp nerves and subodontoblastic blood vessels

in restorative tx –> carious invasion = stim release of growth factors in min.dent.matrix = stims dentinogenesis
- traumatic cav prep = more rapid dentinogensis

inwards fluid shifts
- produced by cutting burs/vibrations
- causes frictional heat, osmotic movement of cooling water
- heat from light curing

outwards fluid shifts
- produced by evap by air cooling/blowing, applying hypertonic conditioners, primers, varnishes, bonding agents

fluid shifts create:
- pain in unanaethetisesed pulps
- local pulpal inflammation under irritated tubules
- alteration in pulpal BF
- ^ tx pressure

26
Q

briefly describe the effect of shallow and deep restorative tx on the odontoblastic layer

A

**shallow restorations **
- disrupt junctional complexes between odontoblasts
- allows large molecules to penetrate pulp
- loss of cell signalling [as collagen matrix no depo in coodinated manner]

deep restorations
- can aspirate odontoblasts

27
Q

describe hypodontia

A
  • most prevalent dentofacial malformation in huamsn
  • developmental failure of six or fewer teeth
  • may occur as part of genetic syndrome or as isolated trait
28
Q

describe cemetum and its FIVE functions

A

cementum
- in healthy mouth = not visible
- NO nerve supply - avascular = receives nutrition from PDL space

functions
- protective func to tooth
- less susceptible to resorption than BONE
- seal for dentin tubules
- covers root surface
- attachment for PDL that hold tooth in socket

29
Q

describe the chemical composition of cementum

A

45-50 % inorganic
-HA crystals

50-55% organic
- collagen fibres
- ground substance

bound water

30
Q

describe the physical properties of cementum

A
  • LESS minersalised than dentin /enamel
  • ~ as hard as bone [little less]
  • yellow - slightly more pale than dentin
  • lacks lustre compared to enamel
  • softer than enamel - low abrasion resistance
31
Q

briefly describe the histological composition of cementum

A

mineralised fibrous matrix and cells
- consists of both sharpey’s fibres and non-periodontal fibres
- sharpey fibres [portion of PDL that are inserted to outer edge of cementum at 90d]

cementum can be classified as
1. presence or absence of cells
- acellular or cellular cementum

  1. nature of organic matrix fibres
    - extrinsic or intrinsic cementum
  2. combination of above
32
Q

describe acellular cementum

A
  • role = provides attachment
  • immediately overlies dentin
  • depo by epithelial root cells before the root sheath cell layer disintegrates
  • formed completely before depo of secondary cementum begins
  • width never changes
  • forms at slower rate than other types and has no embedded cementocytes
33
Q

describe cellular cementum

A
  • THICKER layer of cementum, covers apical 1/3 of root
  • depo by cementoblasts of PDL [PDL provides nutrition via cementocyte process which are oritented towards PDL]
  • no nerves [relatively avascular]
  • adaptive role in response to tooth wear/ movement
  • faster rate of matrix formation than acellular type
  • cementum thickness ^ towards apex
  • cellular activity ^ towards surface
34
Q

describe the extrinsic and intrinsic fibres of cementum

A

extrinsic
- sharpey’s fibres = portion of collagen fibres from PDL that are partially inserted –> outer cementum at 90d
- continues into cementum in same direction of insertion

intrinsic
- derived from cementoblasts, parallel to root surface at ~ 90d to extrinsic fibres

35
Q

list the statistics of the CEJ morphology

A

60% overlap
30% meet
10% gap

36
Q

describe FOUR reasons for changes in cementum

A
  1. age related changes
    - surface irregularities
    - apical canal narrowing
    - reversal lines
  2. cemental repair
    - cells programmed to maintain smooth root surface after resorption occurs
    - defects from traumatic occlusion, tooth movement, hyper-eruption
  3. loss of cementum
    - accompanied by loss of attchment fibres to root surface
    - repair cementum may be depo by cementoblasts in defect –> attachment fibres readily appear]
  4. external resorption of root surface
    - damage followed by reparative phase
    - new cementum depo over previously resorbed surface
    - in early repair phases = reparative cementum typically composed of cellular cementum lacking sharpery’s fibres [does not contribute to tooth anchorage]
37
Q

describe the effects of hypercementosis, caries and concresence on cementum

A

hypercementosis
- excessive cementum formation on roots = bulbous appearance
- cause = not always clear by can occur from chronic inflammation/ irritation of PDL, trauma/ injury to tooth, genetic predisposition

caries
- risk of cemental caries ^ w age, as gingival recession occurs from either trauma or perio

concresence
- union of root structure of two or more teeth by cementum
- causes complications in extractions

38
Q

briefly describe the alveolar bone and its chemical composition

A
  • part of max/mand which supports teeth roots [=existence entirely dependent on presence of teeth]
  • develops by intramembranous ossification

chemical comp
- 60% inorganic/ mineralised
- 25% organic material
- 15% water
- mainly calcium HA [Ca10(PO4)6(OH)2]
- potassium, magnesium, manganese silica, iron, zinc also present [small amounts]

39
Q

outline the gross anatomy of the alveolar bone

A

cortical plate [buccal/lingual]
- compact bone w/ periosteum

cribriform plate [socket wall]
- radiographically = lamina dura
- its presence indicates health of periapical tx

cancellous bone
- spongey bone trabeculae w/ bone marrow spaces in between

40
Q

define and list the functions of oral mucosa

A

mucous membrane - lines any body cavity which communicates w external environment [nasal, oral, GI tract]

functions
1. protection
- from mechanical forces during mastication
- compression, stretching, shearing and from surface abrasions from hard particles in diet

  1. sensation
    - info about events in oral cavity ; temp, touch, pain, taste
    - reflexes; swallowing, gagging, retching, salivating = iniated by receptors in oral cavity
  2. secretions
    - major + minor salivary glands + sebaceous glands
41
Q

describe the cell renewal and shedding in the oral epithelium

A

constant renewal = important defence mechanism

cells arising from mitotic division in basal layer mature and undergo differentiation as they passively migrate to surface to replace cells that have shed
- keratinised [cytoplasm of OUTERMOST epithelium = replaced by keratin]
- non keratinised

shedding
cell lipid content = water barrier, attached tgt by mod. desomosome =undergoes breakdown to permit desquamation [shedding]

regional differences in patterns of epithelial maturation associated w different cell turnover rates

da cursed tooth (5 decks)

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