Dentine structure Flashcards
what is the percentage composition of mineral in dentine by weight?
70%
what is the percentage composition of matrix by weight?
20%
what is the percentage composition of water by weight?
10%
what is the mineral of dentine made up of?
hydroxyapatite
what is the matrix of dentine made up of?
collagen
what are the directions of the collagen fibres in the dentine? why?
parallel to ADJ to give strength
the tubules in dentine are wiggly, why?
Dentine grows inward, this pressure causes tubules to be wiggly
what forms dentine?
odontoblasts
the contents of dentine tubules can be what 3 things?
no cell processes just dentinal fluid
odontoblast process
odontoblast process and nerves
how far through dentine does odontoblast process extend?
roughly 1/3 the way through dentine so outer 2/3rds unlikely to expose process or nerve innervations
where is dentine more innervated?
closer to the pulp
why wont acid etching diffuse into the pulp?
due to pulpal pressure and hydrostatic pressure of dentinal fluid moving outwards of exposed tubules
name 3 ways dentine is classified
developmental
primary, secondary, tertiary
tubule
what are the types of developmental dentine classification?
mantle dentine
circumpulpal dentine
what developmental classification of dentine is this?
mantle
what developmental classification of dentine is this?
circumpulpal
what is mantle dentine?
First formed dentine adjacent to enamel.
describe the collagen fibrils in mantle dentine
Large collagen fibrils at 90 degrees to ADJ - disadvantageous as angle where demineralisation is more likely
what is circumpulpal dentine?
the rest of the dentine that surrounds the pulp and makes up most of the dentine
describe the collagen fibrils in circumpulpal dentine
Small collagen fibrils parallel to ADJ
which is more mineralised, mantle dentine or circumpulpal dentine?
circumpulpal dentine
what is primary dentine?
Formed during tooth development, stops when root is complete (2/3yrs after eruption)
what is secondary dentine?
forms after the root is fully developed throughout life.
why are endodontic procedures harder in older teeth?
vital pulp enables continuous formation of secondary dentine which shrinks the pulp chamber
what is tertiary dentine?
dentine forms in response to insult
what is reactionary dentine?
in response to mild stimulus
uses existing odontoblasts to make secondary dentine
what is reparative dentine?
in response to strong stimulus
no existing odontoblast so recruit newly differentiated odontoblasts hard tissue wall forms to slow down carious pathway to protect pulp
what tubule classification of dentine is this?
inter-tubular dentine
what tubule classification of dentine is this?
peri-tubular/intra-tubular
what is Peri-tubular or intra-tubular dentine?
Around tubules
what is inter-tubular dentine?
Between tubules
which is more mineralised, peri/intra-tubular or inter-tubular dentine?
peri/intra-tubular dentine
what are these lines?
incremental lines of von ebner
what do the incremental lines of von ebner represent?
the position of the odontoblasts at different times during development
what is this line?
contour line of owen
what is the contour line of owen?
coincidence of secondary curvatures
what is globular dentine?
failure of calcospherites to fuse
what is the granular layer of tomes?
hypomineralized area of radicular dentin
name three ways dentine responds to insult
tertiary dentine
sclerosis
dead tracts
what is sclerosis?
highly mineralised - precipitation of calcium and phosphate which block off tubules so appear transparent
what are dead tracts?
odontoblasts die, empty tubules sealed with reparative tertiary dentine so appear darker
dead tracts are caused by what two things?
Could be due to insult or overcrowding of odontoblasts
how does dentine change as we get older?
more secondary dentine -> smaller pulp chamber
more sclerosis -> more transparent and easily fracture when extracted due to being less flexible as more mineralised
