Podcast
Questions and Answers
What is gnarled enamel characterized by?
What is gnarled enamel characterized by?
- Thin and brittle structure
- Irregular twist intertwining (correct)
- A uniform appearance throughout
- Smooth and polished surface
What do Hunter-Schreger bands signify in enamel?
What do Hunter-Schreger bands signify in enamel?
- Regions of crystallization
- Lipid deposits
- Areas of enamel caries
- Different permeability zones (correct)
What is represented by the striae of Retzius?
What is represented by the striae of Retzius?
- Permanent enamel alteration
- Environmental exposure lines
- Dentin caries progression
- Rhythmic deposition of enamel (correct)
The neonatal line in enamel indicates what kind of transition?
The neonatal line in enamel indicates what kind of transition?
What is unique about the dentinoenamel junction?
What is unique about the dentinoenamel junction?
How are incremental lines or striae of Retzius observed in a longitudinal section of a tooth?
How are incremental lines or striae of Retzius observed in a longitudinal section of a tooth?
How many striae of Retzius are estimated not to reach the surface?
How many striae of Retzius are estimated not to reach the surface?
What aspect of enamel structure is implied by the scalloped appearance of the dentinoenamel junction?
What aspect of enamel structure is implied by the scalloped appearance of the dentinoenamel junction?
What are enamel spindles primarily composed of?
What are enamel spindles primarily composed of?
Which factor primarily contributes to the wear facets observed in older individuals?
Which factor primarily contributes to the wear facets observed in older individuals?
What happens to perikymata as a person ages?
What happens to perikymata as a person ages?
How does aging affect the permeability of enamel?
How does aging affect the permeability of enamel?
What is attrition in dental terms?
What is attrition in dental terms?
What can predispose enamel structures to caries?
What can predispose enamel structures to caries?
Which process leads to the loss of tooth structure caused by mechanical force?
Which process leads to the loss of tooth structure caused by mechanical force?
What type of wear is caused by acidic substances in foods or drinks?
What type of wear is caused by acidic substances in foods or drinks?
What are enamel tufts primarily characterized by?
What are enamel tufts primarily characterized by?
Which type of enamel lamellae are poorly calcified and consist of degenerated cells?
Which type of enamel lamellae are poorly calcified and consist of degenerated cells?
What do perikymata represent in enamel?
What do perikymata represent in enamel?
How thick is the relatively structureless layer of enamel?
How thick is the relatively structureless layer of enamel?
What is the main characteristic of enamel cracks?
What is the main characteristic of enamel cracks?
What does the enamel cuticle cover?
What does the enamel cuticle cover?
What are enamel spindles associated with?
What are enamel spindles associated with?
What are Hunter-Schreger bands primarily associated with?
What are Hunter-Schreger bands primarily associated with?
What is the fundamental structural unit of enamel?
What is the fundamental structural unit of enamel?
How do the crystals in the interrod region differ from those in the enamel rods?
How do the crystals in the interrod region differ from those in the enamel rods?
What shape do enamel rods typically appear as in a cross section under a light microscope?
What shape do enamel rods typically appear as in a cross section under a light microscope?
What is the composition of the narrow space separating the rod and interrod enamel?
What is the composition of the narrow space separating the rod and interrod enamel?
What are the shapes of prisms found in the enamel known as?
What are the shapes of prisms found in the enamel known as?
What is the shape of enamel rods in transverse section?
What is the shape of enamel rods in transverse section?
Which parts form the enamel rod?
Which parts form the enamel rod?
What are enamel rods primarily composed of?
What are enamel rods primarily composed of?
How long can enamel rods range in length?
How long can enamel rods range in length?
What direction do enamel rods maintain in relation to the dentin surface?
What direction do enamel rods maintain in relation to the dentin surface?
What characteristic appearance do segments of enamel rods give?
What characteristic appearance do segments of enamel rods give?
How do the lengths of enamel rods in the cusp region compare to those in the cervical region?
How do the lengths of enamel rods in the cusp region compare to those in the cervical region?
What occurs to the appearance of enamel rods when viewed in an oblique plane near the dentin?
What occurs to the appearance of enamel rods when viewed in an oblique plane near the dentin?
Flashcards
Enamel Rods
Enamel Rods
Basic units of enamel, extending from the dentino-enamel junction (DEJ) to the enamel surface.
Dentino-enamel junction (DEJ)
Dentino-enamel junction (DEJ)
Boundary where enamel and dentin meet.
Rods (Prisms)
Rods (Prisms)
Enamel's structural units arranged in a pattern
Interrod Enamel
Interrod Enamel
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Rod Sheath
Rod Sheath
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Enamel Rod Shape
Enamel Rod Shape
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Enamel Rod Formation
Enamel Rod Formation
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Enamel Rod Composition
Enamel Rod Composition
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Enamel Rod Dimensions
Enamel Rod Dimensions
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Enamel Rod Hexagonal Shape
Enamel Rod Hexagonal Shape
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Enamel Rod Direction
Enamel Rod Direction
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Enamel Rod Length Variation
Enamel Rod Length Variation
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Enamel Rod Striations
Enamel Rod Striations
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Gnarled Enamel
Gnarled Enamel
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Hunter-Schreger Bands
Hunter-Schreger Bands
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Incremental Lines / Striae of Retzius
Incremental Lines / Striae of Retzius
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Striae of Retzius Formation
Striae of Retzius Formation
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Neonatal Line / Ring
Neonatal Line / Ring
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DEJ Composition
DEJ Composition
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DEJ Appearance
DEJ Appearance
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Incremental Lines of Retzius
Incremental Lines of Retzius
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Neonatal Lines
Neonatal Lines
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Perikymata
Perikymata
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Enamel Cuticle
Enamel Cuticle
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Enamel Lamellae
Enamel Lamellae
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Enamel Spindles
Enamel Spindles
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Enamel Tufts
Enamel Tufts
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Age Changes in Enamel
Age Changes in Enamel
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Attrition
Attrition
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Enamel Permeability
Enamel Permeability
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Causes of Enamel Erosion
Causes of Enamel Erosion
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Effect of Structure Loss on Caries
Effect of Structure Loss on Caries
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Acid Etching of Enamel
Acid Etching of Enamel
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Study Notes
Enamel Structure Age Changes - Clinical Considerations
- Enamel is composed of closely packed, rod-like crystals of apatite.
- Enamel rods are the fundamental unit, extending from the dentino-enamel junction (DEJ) to the outer surface.
- The interrod region (interprismatic substance) surrounds each rod, with different crystal orientation than the rod itself.
- A narrow space containing organic material (rod sheath) delineates the boundary between rod and interrod enamel.
- Enamel rods are clear crystalline structures allowing light to pass through.
- Cross sections under a light microscope resemble hexagonal/round/oval fish scales.
- Some appear as keyhole or paddle shapes.
- In transverse section, enamel rods have a keyhole shape.
- The head is formed by the rod itself, commonly directed towards the incisal or occlusal aspect.
- The tail is formed by the interrod, directed towards the cervical region.
- Enamel is formed by ameloblasts and each ameloblast contributes to four different rods.
- Enamel rods have segments, separated by dark lines, exhibiting a striated appearance.
- Segment length is approximately 4 micrometers.
- Rods are oriented at right angles to the dentin surface.
- Deciduous teeth's rods are approximately horizontal in the cervical and central regions, becoming increasingly oblique in the cusp region.
- Permanent teeth's rods are similar in the occlusal third but deviate from horizontal in the cervical region.
Enamel Structures Seen in Enamel
- Enamel Rods
- Hunter Schreger Bands
- Incremental Lines of Retzius
- Neonatal Lines
- Perikymata
- Enamel cuticle
- Enamel cracks
- Enamel lamellae
- Enamel Spindles
- Gnarled Enamel
- Enamel Tufts
- Dentinoenamel Junction
- Odontoblastic Processes
Age Changes in Enamel
- Attrition/wear of occlusal/proximal contact points of mastication.
- Wear facets are increasingly pronounced in older individuals.
- Perikymata disappear completely.
- Generalized loss of and gradual flattening of perikymata.
Clinical Considerations
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Post-developmental loss of tooth structure (attrition, abrasion, erosion) is possible.
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Cavity preparation impacting enamel rods.
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Deep enamel fissures and dental lamellae predispose teeth to caries.
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Enamel is 30 micrometers thick, relatively structureless; no prism outlines are visible.
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Apatite crystals are parallel to each other and perpendicular to the striae of retzius.
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Enamel is heavily mineralized compared to the underlying dentin.
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Perikymata are transverse wave-like grooves, reflecting striae of Retzius.
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Enamel cuticle is a delicate Nasmyth's membrane covering newly erupted teeth, eventually worn away by mastication.
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Erupted enamel is coated with pellicle (precipitate of salivary proteins).
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Enamel lamellae are thin, leaf-like structures extending from the enamel surface to the DEJ, sometimes penetrating dentin; they are hypomineralised.
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Enamel tufts are ribbon-like structures originating at the DEJ, extending to about 1/5 or 1/3 of the enamel thickness, and aligned with the crown's long axis.
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Enamel spindles are slender projections of underlying odontoblasts traversing the DEJ. Their organic content disintegrates in dried teeth, leaving air spaces that appear dark in transmitted light.
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Change in enamel permeability in older teeth, due to increased crystal size and decreased porosity.
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