CSA histology of enamel and dentine caries Flashcards
What is enamel like?
- brittle so relies on dentine for resistance
What is enamel pure mineral like?
3% water, 1% protein (non-collagenous) and 96% HAP:
Where is enamel most thick?
incisal edge
What are HAP crystals ordered in ?
prism/rod runs from dentine (ADJ) to below tooth surface
-Approx. 5um in diameter
What are prisms like in longitudinal sections?
perp. to ADJ
What is enamel production like?
• Circadian rhythm in enamel production = , daily, cross-striations w/ 5um periodicity:
What are Striae of Retzius (brown incremental lines)
superimposed on 5um periodicity
o Towards cusp = irregularly spaced but more regular towards cervical margin
When are tuft proteins seen?
enamel crown = completely removed with acid (demineralised)
What is tuft protein ?
areas in between prisms where enamel proteins collected
When are tufts seen
transverse section
what are prisms in tufts like
- Prisms = change path at each level
- High protein content at prism boundaries = superimposed on each level
What are spindles?
odontoblast process crossing forming ADJ into developing enamel during crown development
Where do spindles originate ? ( cigar shape)
at ADJ into enamel
What are seen in longitudinal sections?
- Striae of Retzius
- Enamel Spindles (also see in thick transverse sections)
- Scalloped Nature of ADJ
- Gnarled Enamel
- Hunter-Schreger Bands
- Cross Striations of Enamel Prisms
What are striae of retzius?
Incremental growth lines = obliquely across prisms to
approach enamel surface
What are striae of retzius associated with at surface?
depressions called Perikymata
What does scalloping of ADJ do ?
aids retention of enamel to dentine + resists shearing forces (more irregular + incr. SA at point of contact between enamel/dentine)
What are enamel spindles?
- Continuous w/ dentinal tubules across ADJ
What are enamel spindles due to ?
odontoblast process crossing the forming ADJ into developing enamel during crown development which leaves a void
What is gnarled enamel ?
-Evolved to resist incr. loads and decr. shearing forces at cusps
What does gnarled enamel look like ?
- On sides of crown, prisms run in straight lines perp. (90 to ADJ)
- At cusp tip) prims = appear more disordered
What are cross striations?
Represent daily incremental growth lines + give prisms ladder appearance
What are HS bands?
Optical effects due to longitudinal sectioning of alternating paths of prisms
Where are HS bands only visible?
inner 2/3rds of enamel
What are prisms like in outer 1/3 of enamel?
parallel
What is Aprismatic Enamel?
region under surface where prism not evident as crystals parallel to each other here
What is white spot lesion?
translucent, dark,
surface and body of lesion
-Partial demin. >striae of Retzius/daily cross striations = appear more distinct
Is fissure lesion smaller than white spot lesion?
yes
What is translucent zone?
Approx. 1% of mineral = lost
What is dark zone?
-Some remin. = occurred here
Diff. range of sizes = causes light scattering so get dark
What is surface zone ?
intact zone, appears to be independent of F- conc.
What are dentinal tubules
•Channels run from pulp to outer dentine
What do dentinal tubules contain ?
fluid and odontoblasts (form/maintain dentine)
What do tubules follow?
S shapes paths (primary cirvature)
- get secondary curvatures superimposed onto S shape
when are tubules branched
at ADJ
What is interglobular dentine ?
incomplete fusion of calcospherites) with mineralising front as dentine
What are calcospherites ?
islands of mineralising dentine)
what does incomplete fusion do ?
traps poorly mineralised dentine matrix = arched shape
What is dentine divided into ?
primary or 2nd dentine
what is in coronal dentine ?
mantle and circumpulpal dentine
When is mantle dentine formed?
first + laid adjacent to ADJ
What are collagen fibres arranged in mantel dentine ?
arranged perp. to ADJ + arise from sub-odontoblastic mesenchyme
When is primary dentine laid down?
give tooth overall shape
When is secondary dentine laid down
slower rate of dentine production at pulpal surface throughout tooth’s life
What are dead tracts?
NO fluid, cell process, mineral deposits
- Fill with debris during sectioning process
- produces black appearance
what are layers of pulp/dentine interface?
- Mineralised dentine
- Pre – dentine (unmineralised apart from calcospherites)
- Odontoblasts
- Cell Free Zone (of Weil)
- Cell Rich Zine
- Body of Pulp (loose, vascular and well innervated connective tissue)
Where is pre dentine layer?
present between odontoblast layer and advancing mineralised front of mineralised dentine
What are odontoblasts responsible for?
forming and maintaining dentine
What do odontoblasts secrete initially?
collagenous matrix (pre – dentine) = subsequently mineralised (partly due to calcospherites fusion)
What does Odont. layer contain?
incr. unmyelinated nerve fibres and capillary loops (arise from sub-odontoblastic plexus = includes cell free/cell rich zone and nerve plexus of Raschkow)
What is cell free zone?
beneath odont. layer
What does cell rich zone?
contains conc. of cell nuclei
What is body of pulp made up of?
loose connective tissue
- Fibroblast = main cell type
- Macrophages
- Undifferentiated mesenchyme
- incr. nerves/capillaries here = supply o.layer and pulp itself:
Where is undifferentiated mesenchyme ?
present in sub-odontoblastic location = differentiates into cells to replace damaged odontoblasts
how do nerves enter to supply Odont.layer and pulp?
through apical foramen
o incr. nerve ending between odontoblasts or within tubules
o incr. looped capillaries within o.layer
does a lesion in dentine spread wider than lesion in enamel ?
YES , due to enamel prism arrangement around fissure + due to lateral spread at ADJ)
What is sclerotic/translucent dentine ?
full occlusion of tubules by peritubular dentine laid down by o.process
When does sclerotic/translucent dentine occur?
ageing process or defensive response to trauma (e.g. caries)
What is dead tract/
Empty tubule left behind fills with air/debris during sectioning process appear black
When is reparative dentine produced ?
surviving odontoblasts to seal dentinal tubules to prevent bacteria/toxins from directly causing damage to pulp
What is reactionary dentine ?
If odontoblasts killed by rapid lesion then sub-odontoblastic cells seal tubules by producing non-tubular bone like material
