Enamel Flashcards
Where is enamel located?
Covers the entire anatomical crown
What kind of fluoride is beneficial at all ages?
Topical fluoride (post-eruptive)
What type of fluoride in beneficial only during amelogenesis?
Systemic fluoride (pre-eruptive)- ingested during odontogenesis
Characteristics of formed enamel
No viable cells, no blood supply, no reparative capabilities
What factors cause demineralization of formed enamel?
External factors: bacterial acids lower oral pH to < 5.5
What is the color of enamel? What determines it?
Ranges from yellow to blue-white
Depends on translucency
Incisal edges are whiter/more translucent
Bulk of crown yellow/white
Darkens with age
Primary teeth are whiter
What is attrition?
Slight to excessive natural wearing process of functional occlusal contact
What is bruxism?
Excessive/traumatic grinding and/or clenching causing severe occlusal wear
What is abrasion?
Mechanical wearing of tooth surface by forces other than mastication
What is erosion?
Loss of tooth structure by a chemical process other than bacterial
What is abfraction?
Loss of tooth tooth structure by biochemical loading forces, flexure and chemical fatigue degradation of enamel (cervical area) distant from loading point
What are the inorganic components of enamel?
96% mineral- calcium hydroxyapatite, carbonate, magnesium, potassium, sodium and fluoride ions
What are the main organic components of enamel?
2% enamel matrix (enamel protein fibers)
- Enamelin
- Amelogenin
- Ameloblastin
- Tuftelin
1-2% water
What is the function of enamelin? Where is it found?
Matrix formation and crystal growth
Present throughout formed enamel
What is the function of amelogenin? What happens to it?
Matrix formation
Separates and supports crystal growth
Completely resorbed by ameloblasts during mineralization
What is the function of ameloblastin?
Crystal elongation and mineralization
What happens to amelogenin and ameloblastin?
Get resorbed by ameloblasts to allow the hardening of enamel
Backfills it with minerals after resorption
What is the function of tuftelin? Where is it located?
Mineralization and structural organization
Increased amount at DEJ and on surface of growing crystals
Some gets left behind after resorption
What is the embryonic origin of enamel?
Ectoderm
Ectodermal lining in stomodeum gives rise to primary dental lamina= enamel buds and organs
EPITHELIAL
What happens during the bud stage?
Enamel organ (dental lamina) formed
What happens during the cap stage?
Inner enamel epithelium forms
What happens during the bell stage?
Pre-ameloblasts formed
What happens during apposition?
Ameloblasts form
What happens during termination?
Post-ameloblasts form (reduced enamel epithelium)
What is amelogenesis?
Enamel matrix formation
Occurs in response to mantle dentin formation
What happens during the first wave of enamel matrix formation?
Matrix formed in incisal or occlusal area
Starts closest to the DEJ and moves toward non-masticatory surfaces
What happens during the second wave of enamel matrix formation?
Growth overlaps the first wave moving cervically toward the CEJ and continues until the crown is completed
In what order does mineralization occur?
First stage follows the same wave pattern
How many ameloblasts form an enamel rod?
The head is formed by one ameloblast, the tail is formed by three
Which direction do the crystals run in enamel rods?
Crystals run parallel to the long axis of the rod
What is the rod sheath? Where is it located?
Organic/protein covering of the enamel rod
Located between the rod and inter rod substance
What direction do crystals run in inter rod substance?
Crystals run perpendicular to the rods
Orientation is opposite to the crystals of enamel rods
What are daily imbrication lines?
Demarcate the daily production of enamel matrix
Similar to “lines of von ebner”
Run perpendicular to enamel rods
What are striae of Retzius?
Represent the successive apposition of different layers of enamel during crown formation
Arches/rings that run perpendicular to rod/prism
Intermittent, overlapping areas seen on the labial surface
What are perikymata?
Shallow grooves between striae of retzius
What are neonatal lines?
Metabolic shock of birth recorded in enamel
Accentuated striae of retzius
What tissues form the DEJ? What does it replace?
Mantle dentin and apristmatic enamel
Replaces the basal lamina/basement membrane
How is the DEJ shaped?
Scallop shaped
Enamel side is convex
Dentin side is concave
Where are enamel spindles found?
Only at the DEJ
Extends from dentin through DEJ into enamel
What is the clinical significance of enamel spindles?
Clinical significance unknown
What are enamel spindles?
Linear defects of entrapped terminal ends of odontoblastic processes
Does not belong, supposed to be in dentin
Where are enamel tufts found?
Only at DEJ on enamel side and extend into enamel
What is the function of enamel tufts?
May help prevent enamel fractures
Creates space for flexture
Where are enamel lamellae found?
Extend in enamel from outer surface or vice versa from the DEJ
May extend to and through the DEJ into circumpulpal dentin
What is the clinical significance of enamel lamellae?
Clinical significance unknown
What is gnarled enamel formed by?
Formed by diverging paths of enamel rods/prisms
Where is gnarled enamel found?
Found under cusps, preventing cusp fractures by reducing stress
What are Hunter Schreger bands?
Dark and light bands of reflected oblique light on enamel
Visible only w/ reflective light microscope
What are Diazones?
Dark bands
Wjhat are parazones?
Light bands
What is the primary enamel cuticle?
AKA Nasmyth’s Membrane- protective enamel covering that wears away after eruption
Acellular, non-calcified substance produced by post-ameloblasts
What is the secondary enamel cuticle?
AKA Acquired pellicle
Acellular, amorphous, organic, tenacious, insoluble protein membrane
Made from salivary glycoproteins and sulcular glycoproteins
Covers the teeth and entire mouth
