Enamel
Avascular & acellular & non-dynamic once its gone with caries/acid/dental wear/other teeth, cant grow back
- Non-inverted (conductivity), doesn’t feel things, but transfers hot/cold to dentin
- Aesthetic good looking, hard, strong, glass like, durable and repairable
Chemical changes in enamel
- Ph<5.5 demineralization
* Ph>5.5 remineralization
Enamel
Amelogenesis ONLY BEFORE tooth erupts (ameloblast
-Ectodermal (starts at dej and forms out) (odontoblast work the other way- dentinogeneis dej-> Inner tooth
Enamel dimensions
Healthy young tooth (2-2.5mm), thick enamel, worn over time
Enamel components
90-92% inorganic (hydroxyapatite crystals)
1-2% inorganic (protein- doesn’t do anything, was there for amelogenesis)
4-6% water
Enamel rods
5-12 mil enamel rods (dej to outer surface of tooth), slightly longer then the enamel region its in b/c slightly curved, no interruptions or branching, (wider at tooth surface, tear shaped)
- rods connected by water and protein, meets dej at 90 degrees
- rods almost 100% apatite crystals, have millions of hydroxyapatite crystals, flouroappetite are added when fluoride treatment
Color? enamel
enamel can change its color b/c permeable, hydroxide between to interod sheath is teeth whitening
Xray
mineralized, more opaque (white) on xray
Root surface
cementum and PDC (no enamel- so no dej on root surface)
Dentin
Most of the tooth is dentin, support enamel and restorations, sensitive and conductive, porous and dynamic, flexible, like pulp
Dentin formation
Dentinogenesis and odontoblast don’t go away after the tooth has erupted (unless root canal where pulp is removed), can make new dentin, which makes the pulp smaller
Dentin Xray
More radiolucent then enamel
Healthy tooth
cej covers dentin, old people gums recede/ naked dentin
Dentin tubules
- Dentinal tubules (dej to pulp, tapers (smaller at the dej), branch especially near periphery (dej), tubes not uninterrupted, can cross over) hollow after extracted, dentin fluid/ cells in is if alive (dentin pulpous)
- Builds in(new dentin forms inwardly) but branches out
Dentin parts
Dentin tubules, peritubular dentin, interlobular dentin
Peritubular dentin
Peritubular dentin- around the tube, more mineralized
Interlobular dentin
Intertubular dentin- dentin between the tubes, like cooked spaghetti, type 1 collagen (organic matter) intertwine, no organization, a lot of small hydroxyapitite crystals and h2o between tubes/ this is why its hard to bind other things to it
Porous??
- Pulp very porous, tubes are wider and closer together
- Dej not porous, tubes smaller diameter and farther apart
Odontoblasts
- One odontoblast (tomes fiber)- cell body (columnar, send process to tubules), cell process (skinny worm like-towards outer part of dentin)
- Odontoblastic process surrounded by dentinal fluid
Dentin differences
Dentin different near pulp (more water) and near dej (less intertubule dentin)
Dentin components
Heterogeneous (50% inorganic appetite crystals,5-25% water, 5-25% organic collagen) and dynamic
Primary Dentin
Dentin there when tooth erupts in the mouth, dentin made by odontoblast when the tooth was developing at the same time for ameloblast to make Enamel, more organized, Forms RAPIDLY going in toward the pulp
Secondary Dentin
after erupt signal odontoblasts doesn’t stop but SLOWS down , more irregular shape
Physiological secondary dentin-
Slow making of dentin, normal as the dentin is bigger and the pulp is getting smaller, in response to ageing
Reparative dentin
secondary, dentin made in response to trauma (carries or punch to mouth), Protection create thicker walls to protect the pulp, can discolor
-Both stop when run out of pulp
Sclerotic dentin-
Sometimes the peritubular dentin lays down more dentin and the tube gets smaller, make the peritubular thicken up, and decreases the permeability of the dentin, Decreases sensitivity-> unless the trauma is so aggressive, rapidly progressing dentin/ but it’s subjective in diff ppl
Aging pulp
Young thick pulp, old thin pulp
Inury progression steps
(dentin injury is reversible) tubules sclerose (dimeter tubule gets smaller, peritubular gets bigger), reparative dentinogeneisis, pulpal inflammation, pulp recovery or necrosis (tooth needs to be extracted/ root canal)
Things that change dentin
The morphology, histology & chemistry of dentin depend on the age of the patient and the wear & tear that the tooth has endured!
DEJ
If healthy cant separate
Caries separate them
Pulp, whats in it
Arterioles and venules enter and leave through small formina, not collateral circulation, no space for expansion (highly vascularized) bigger apically then smaller towards the end that leaves the venous system
Pulp
- Formative (useful for making dentin) and protective (allows us to feel pain)
- Vey vascularized, collagen and ground substances, formative, defense, sensory innervation, motor innervation(dilate and constrict bv)
Pulp fibers
- C fibers- respond to inflammation (low burning pain)
- A-alpha and a-detla fibers -> respond to fluid movement in tubules (hsarp quick pain) on the walls of the pulp around the cell bodies, zone of weil
- Only feel pain, not if its hot or cold
Cementum
Cover the clinical root, CEJ, acellular (mostly fibers) but cellular in the apical third, hard like bone, thickness varies, supportive,