What is the composition of dentin?
70% mineralized inorganic material, 20% organic material, and 10% water
Why is dentin continually produced throughout life?
because of the retention of the odontoblasts along the outer pulpal wall
What do the calcium hydroxyapatite crystals form as during the primary mineralization?
globules or calcospherules, in the collagen fibers of the predentin, expanding and fusing together
What is globular dentin?
areas where primary and secondary mineralization have occured with complete crystalline fusion
What is interglobular dentin?
areas where primary mineralization within the pre-dentin, and the globules of dentin did not fuse completely
Where is interglobular dentin especially evident?
in coronal dentin and near the DEJ, and in certain dental anomalies
What are dentinal tubules?
long tubes in the dentin that extend from the DEJ in the crown area or the DCJ in the root area to the outer wall of the pulp
What can be contained inside the dentinal tubule?
hollow space, dentinal fluid, an odontoblastic process, and possibly an afferent axon
How do odontoblasts in the mature dentin attain nutrition?
by way of the dentinal tubule from tissue fluid originally from blood vessels located in the adjacent pulp tissue
What is dentinal fluid?
tissue fluid surrounding the cell membrane of the odontoblast, which is continuous to the cell body in the pulp
What is an odontoblastic process?
a long cellular extension located within the dentinal tubule and still attached to the cell body of the odontoblast within the pulp
Does the odontoblastic process run the entire length of the dentinal tubule?
it may or may not extend the full length to the DEJ or DCJ
What does the secondary curvature resemble?
small delicate curves noted in the primary curvature, noting smaller daily changes in odontoblast direction
Between peritubular and intertubular dentin, which is more mineralized than the other?
Why is mantle dentin more mineralized than inner portions of dentin?
because it contains more peritubular dentin
What is primary dentin?
dentin formed in a tooth before the completion of the apical foramen of the root, has a regular pattern of dentinal tubules
What is secondary dentin?
dentin that is formed after the completion of the apical foramen and continues to form throughout the life of the tooth, formed more slowly and is less mineralized
What is tertiary dentin?
dentin that is formed quickly in localized regions in response to a localized injury to the exposed dentin
Where is tertiary dentin located?
forms underneath the exposed dentin's tubules along the out pulpal wall
What is sclerotic dentin?
type of tertiary dentin, associated with chronic injury of caries, and also in noted to increase with age
What type of dentin does the odontoblastic processes die and leave the dentinal tubule hollow, but then becomes retrofilled and occluded by a mineralized substance similar to peritubular dentin?
What is the odontoblastic layer?
this layer lines the outer pulpal wall and consists of the cell bodies of odontoblasts. secondary dentin may form in this area from the apposition of these odontoblasts, causing the cell bodies to realign themselves. cell bodies of the afferent axons from the dentinal tubules are located between cell bodies of the odontoblasts
What is the cell-free zone?
this zone contains fewer cells than the odontoblastic layer. the nerve and capillary plexus is located here
What is the cell-rich zone?
the zone contains an increased density of cells compared with the cell-free zone and also has a more extensive vascular system