Structure of Enamel and Dentin (Larsen 4) Flashcards
______ covers the anatomical crown. It is thickest over the _____ and decreases in thickness toward the ______.
- Enamel
- Cuspal tips
- Cemento-enamel junction
Enamel enables the tooth to _____ and _____ food and protects the _____.
- Grind and crush
- Dentin
Physical Properties of Enamel
- Hardness
- Brittleness
- Color
Enamel is the _______ substance in the body because of the ______ and _____ of hydroxyapatite crystals.
- Hardest
- Number and arrangement
Enamel is very ____ because of the high inorganic content, and has to be supported by _____ to prevent breakage.
- Brittle
- Dentin
Enamel is ______ in color which allow yellow of dentin to come through. The tooth color depends on the ______ of the enamel and the _____ of the dentin.
- Translucent
- Thickness
- Color
Enamel rods extend from their origins at the _____ to the _______.
- Dentinoenamel junction (DEJ)
- Enamel outer surface
The ______ is a bundle of crystal ribbons
Enamel rod
The ______ is between and around rods at a different angle
Interrod
The ______ is a hypomineralized sheath surrounding each enamel rod that contains _______ material (enamel proteins).
- Rod sheath
- Organic
______ are viewed only with reflected light and appear as light and dark bands.
Hunter-Schreger Bands
______ result from the arrangement of hydroxyapatite crystals (orientation of rod and interrod)
Hunter-Schreger Bands
The dark, horizontal ______ on the enamel rod represent daily growth of rod segments and are slightly hypomineralized.
Striations
The ______ are concentric dark bands that follow the contour of the tooth surface and represent _______ areas of rods resulting from 7-11 days of growth or during physiological stress.
- Striae of Retzius
- Hypomineralized
The ______ is an accentuated hypomineralization associated with birth in all primary teeth and first molars of secondary teeth.
Neonatal line
The ______ are horizontal ridges on the surface of the tooth. They are surface manifestiations of the termination of _______.
- Perikymata
- Striae of Retzius
Gnarled enamel is twisted rods of enamel under the _______ which provides _______ against forces of mastication.
- Cuspal tips
- Greater strength
The DEJ is _______ which allows for the attachment of the two mineralized surfaces.
Scalloped
_______ are caused by the movement of ameloblasts from the DEJ. They are enamel rods in different directions that extend 10-20% the distance from ____ to ______ and are ________ (contain enamel protein).
- Enamel tufts
- DEJ to occlusal surface
- Hypomineralized
______ are an extension of the dentinal tubule crossing through the DEJ. They are surrounded by enamel and shorter than tufts.
Enamel Spindles
______ appear as lines extending from the surface toward the DEJ and represent a defect filled with organic material. It is hypomineralized and not tubular.
Enamel Lamellae
Physical Properties of Dentin
- Color (yellow)
- Compressibility and Elasticity (Serves as shock absorber for enamel)
Hardness & Density comparison of Bone, Enamel, and Dentin
Enamel > Dentin > Bone=Cementum
The ______ is a tube that extends from pulp chamber or root canal to either the junction with the enamel (DEJ) or cementum (DCJ).
Dentinal Tubule
Features of Dentinal Tubules
- Odontoblastic Processes
- Nerves and Sensitivity
The ________ of Dentinal Tubules are 3 or 4 brances of cell processes of adjacent cells.
Odontoblastic Processes
The ______ of the Dentinal Tubules may extend 1/3 the distance up the tubule. ______ is when the nerves arise from the pulp and transmit any stimulus as pain.
- Nerves
- Sensitivity
_____ Dentin immediately surrounds the odontoblastic cell process and is hypermineralized, while ______ Denin is the remaining dentin that is not directly surrounding odontoblastic cell process.
- Peritubular
- Intertubular
_____ Dentin makes up the body of tooth and is formed before eruption. Examples are the Mantle and Circumpulpal dentin.
Primary
______ Dentin forms only after tooth eruption. It is internal to primary dentin and borders the pulp.
Secondary
______ Dentin forms only in response to trauma to the pulp in a localized area.
Tertiary or reparative dentin
_____ Dentin forms slowly throughout life. Masticatory forces cause a bending of the tubules.
Secondary
_______ represent major change of physiology during several days of growth in dentin. They are hypomineralized and are equivalent to the Striae of Retzius of the enamel.
Contour Lines of Owen
The _______ is a hypomineralized line caused by birth.
Neonatal line
Dentin formed _____ birth is better quality than _____.
- Prior to
- After birth
______ is produced in response to an insult to a tooth. The _____ form a patch of dentin to protect the pulp. The tubules are sparse and irregularly arranged, and the matrix is poorly mineralized (hypomineralized).
- Tertiary or Reparative Dentin
- Odontoblasts
______ is found in the crown and root. They are ______ areas between globular mineralization fronts.
- Interglobular Dentin
- Hypomineralized
______ are found in the root along the DCJ. They are small hypomineralized spheres that represent the highly branched terminal ends of the odontoblastic cell processes.
Granular Layer of Tomes
After Severe Trauma, a _______ is an area of empty dentinal tubules that generally result from bacteria invasion. Odontoblastic cell processes retreat because of bacterial toxins leaving empty space.
Dead Tract
After Severe Trauma, ________ is hypercalcified dentin under the dead tract that forms a protective barrier.
Sclerotic Dentin
______ is hypermineralized as dentinal tubules are filled in by the constant production of dentin. It is transparent.
Sclerotic Dentin
