Dentin Flashcards
what is the composition of dentin by weight ?
70% inorganic material
30%(20% protein 10% water) organic material
the protein content of dentin is made up of :
90% collagenous protein and 10% non-collagenous protein
what are some physical properties of dentin ?
-pale yellow in color
-elastic quality that provides flexibility and prevents fracture of overlying brittle enamel
-harder than bone
what is primary dentin ?
tooth dentin that is formed before root formation is complete
primary dentin which outlines the pulp chamber is known as ___
circumpulpal dentin
outermost part of circumpulpal dentin is known as ___
mantle dentin
what is secondary dentine ?
dentine secreted after root formation has ended
what are the differences between primary and secondary dentin ?
secondary dentinal tubules are less regular with different orientation
-there is a line of demarcation between primary and secondary dentin that is present due to the difference in orientation
what is tertiary dentin ?
reactive or reparative dentin secreted as a reaction to stimuli such as caries or attrition
- tertiary dentin is secreted only by the cells directly affected
how thick is mantle dentine ?
about 20 microns thick and it is LESS mineralized
what is the organic matrix of mantle dentin formed of ?
thick collagen fibrils called von korffs fibers
these fibers are different becasue they are perpendicular to the DEJ while other collagen fibers are parallel
describe the process of dentin mineralization by globular calcification :
odontoblasts secrete vesicles containing minerals .they are initially small spherical areas ,which become larger and fuse with one another to form calcification front
explain dentin mineralization by liner calcification
minerals are deposited on organic matrix (collagen ) parallel to DEJ
What happens if globules fail to join together during globular calcification?
hypo mineralized space called inter-globular spaces form between the globules
what happens to the organic and inorganic material when preparing a ground section?
organic material is burnt while the inorganic material remains
what course of the dentinal tubule in crown of tooth is___(primary curvature)
S-shaped (primary curvature )
dentine tubules have branches which allow them to communicate with eachother
what is the secondary curvature of dentinal tubules ?
wavy dentinal tubules formed by slight undulations by odontoblast during deposition of dentin
what is the difference between intra-tubular dentine and inter-tubular dentin ?
intra tubular dentine is the dentine that lines the dentinal tubules and it is highly mineralized (is is also known as peri-tubular dentin )
inter-tubular dentine is the dentin found between the dnetinal tubules and it is less mineralized
what is the granular layer of tomes ?
granular layer found in root dentin that can be observed when ground section is examined in transmitted light zone
-dot like hypo mineralized structures found near cementum
incremental lines of dentin that signify cyclic activity are known as:
incremental lines of von ebner. they appear as fine striations in dentin
-they run at a right angle to dentinal tubules and correspond to incremental lines of enamel
where is the cell body of the odontoblast located?
at the pulpal surface (pre-dentin)
what are the contour lines of owen?
accentuated deficiencies in mineralization , highlighter incremental lines of von ebner
what is the neonatal line ?
accentuated contour line separating prenatal and postnatal dentin
