Enamel Flashcards
Ameloblasts having ruffled borders are:
a- Secretory ameloblasts.
b- Maturative ameloblasts.
c- Protective ameloblasts.
d- Transitional ameloblasts.
B
Which of the following is not a feature of enamel?
a- Contour lines of Owen.
b- Cross striations.
c- Prism sheath.
d- Perikymata.
A
Maturative ameloblasts are characterized by having:
a- A distally positioned nucleus.
b- A highly basophilic cytoplasm.
c- A highly-developed Golgi complex.
d-A distal cell membrane with many infoldings.
D
Which of the following does not occur during maturation of enamel?
a- Influx of calcium and phosphorus.
b- Growth of hydroxyapatite crystals.
c- Increase in organic content.
d-Decrease in the water content.
C
Incremental lines are a result of variation in:
a- Proliferation.
b- Histodifferentiation.
c- Morphodifferentiation.
d- Rhythmic apposition.
D
The prismatic structure of enamel is due to:
a- Variation in the density of organic material.
b- Variation in crystal orientation.
c- A rhythmic pattern of apposition.
d- The periodic change in prism direction.
B
The prismless layer of enamel:
a- Is found only in primary teeth.
b- Does not contain prism & prism sheaths.
c- Is found near the amelo-dentinal junction.
d- Contains no hydroxyapatite.
B
Enamel tufts:
a- Contain cellular processes.
b- Can pass to dentin.
c- Are seen in decalcified sections.
d- Are grass like structure.
D
During the maturation stage of enamel formation, which of the following does not occur in the ameloblastic layer?
a- Water absorption.
b- Protein absorption.
c- Change in cellular organelles.
d- Secretion of enamel matrix.
D
When prismless enamel is formed, the secretory ameloblast does not contain:
a- Rough endoplasmic reticulum.
b- Tome’s process.
c- Nucleus.
d- Secretory granules.
B
Which of the following is true:
a- Enamel is the weakly mineralized tissue.
b- Enamel is the highly mineralized tissue
c- Enamel is the highly permeable tissue.
d-Enamel is a non brittle tissue.
B
Neonatal lines are present in:
a- All permanent teeth.
b- Permanent canines.
c- All deciduous & first permanent molar.
d- Premolars.
C
Organic components of enamel are primarily removed from enamel by:
a- Secretory ameloblasts.
b- Maturative ameloblasts.
c- Transitional ameloblasts.
d- Enamel spindle.
B
The main difference between the rod and the interrod region is:
a- Crystal size.
b- Crystal orientation.
c- Crystal composition.
d- In the nature of the organic component.
B
The striae of Retzius:
a- Are parallel to the enamel rods.
b- Are parallel to the surface of the enamel in the cervical region.
c- Are not seen in the cuspal one third of the enamel.
d- Would be seen as concentric rings in a horizontal section of the crown.
D
Enamel is composed of:
a) Rod, interrod & rod sheath.
b) Only enamel prisms.
c) Needle shaped crystals.
d) Prism sheath.
A
The extensions from secretory ameloblast cells that give structure to enamel rods are called:
a) Enamel tuft.
b) Tomes processes.
c) Enamel spindles.
d) Enamel lamellae.
B
Striae of Retzius:
a) Result from enamel crack.
b) Separate prenatal from postnatal enamel.
c) Are due to rhythmic apposition of enamel.
d) Are hypermineralized structure.
C
Enamel Rods:
a) Their number varies in different teeth.
b) Have an average width of 1um.
c) Are Present at the enamel surface.
d) Have a straight course at the cusps of teeth.
A
Enamel is formed of:
a- 76% minerals & 24% organic materials and water.
b- 96% minerals & 4% organic materials and water.
c- 86% minerals & 14% organic materials and water.
d- 99% minerals & 1% organic materials and water.
B
which of the following is absent in all premolars:
a- Enamel spindle.
b- Enamel tuft.
c- Neonatal line.
d- Enamel lamella.
C
Cross striations in enamel:
a- Are an optical phenomena.
b- Result from abrupt change in environment before and after birth.
c- Result from mineralization disorder.
d- Appear to be periodic bands at 4 microns interval across the rod.
D
The prism sheath:
a- Is a dense continuous sheath separating rod from inter-rod.
b- Result from abrupt change in crystals orientation.
c- Is more mineralized than rod and inter-rod.
d- Found in prismless enamel
B
The complex arrangement of rods over the cusps of teeth is termed:
a- Prismless enamel.
b- Gnarled enamel.
c- Prenatal enamel.
d- Postnatal enamel.
B
The origin of enamel is:
a- neural crest cells
b- Ectoderm.
c- Mesoderm.
d- Ectomesenchyme.
B
Hypocalcified areas in enamel are:
a- Enamel spindles.
b- Dentino-enamel junction.
c- Interprismatic substances.
d- Enamel tufts.
B & D
( if you have to choose one answer, go with D)
Prismless enamel:
a- Is less mineralized than prismatic enamel.
b- Is found only in the cervical area of permanent teeth.
c- Is harder than prismatic enamel.
d- Found near the dentino-enamel junction.
C
The perikymata:
a- Is an optical phenomena resulting from changes in direction of enamel rods.
b- Is a highly mineralized outer enamel surface.
c- Is formed of transverse grooves, represents an outer manifestation of brown stria of Retzius.
d- Found at the cusp tip.
C
What is the result of cracks before tooth eruption:
a- Enamel lamella type A.
b- Enamel lamella type B.
c- Enamel lamella type C.
d- Enamel tufts.
B
The primary enamel cuticle is formed by the:
a- Outer dental epithelium.
b- Ameloblasts just before tooth eruption.
c- Fusion of oral epithelium and reduced enamel epithelium.
d- Ameloblasts after the enamel has been completed.
D
The surface enamel:
a- Is similar to the subsurface enamel.
b- Is softer than subsurface enamel.
c- Contains less mineral than subsurface enamel.
d- Highly mineralized than subssurface enamel.
D
The prism sheath:
a- Is a continuous sheath.
b- Is more calcified than the enamel rod.
c- Is less calcified than the enamel rod.
d- Is equally calcified when compared to the enamel rod.
C
The predominant inorganic portion of enamel is:
a- Calcium.
b- Carbonate.
c- Phosphate.
d- Fluoride.
A
Incremental lines of Retzius form grooves on the surface of the enamel termed:
a- Perikymata.
b- Neonatal lines.
c- Gnarled enamel.
d- Enamel cuticle
A
Which of the following is poorly calcified enamel?
a- Gnarled enamel.
b- True enamel lamellae.
c- Perikymata and gnarled enamel.
d- Interprismatic substance.
B
The cross striations characteristic of enamel rods represent:
a- Incremental growth pattern.
b- The junctional complex of ameloblasts.
c- Hunter-Schreger bands.
d- The inter rod region.
A
Enamel spindles:
a- Are areas of prismatic enamel.
b- Are present at the occlusal surfaces of enamel.
c- Are the terminal ends of odontoblastic processes.
d- Are located at the cemento-enamel junction.
C
Which of the following is a true statement about the organic matrix of the newly synthesized enamel?
a- It represents 30% by weight of the organic content.
b- It has a high content of amelogenins.
c- It contains collagen fibers.
d- It has a high inorganic content.
B
Tome’s processes:
a- Contain mitochondria, but lack Golgi saccules and rough endoplasmic reticulum.
b- Lack secretory granules.
c- Indent the immature enamel to produce a serrated outline on its appositional surface.
d- Are located at the proximal end of the ameloblast.
C
Which of the following is the source of nutrient supply to the secretory ameloblasts during early crown formation?
a- Subodontoblastic plexus of capillaries.
b- Central blood vessels in the dental papilla.
c- Dental sac capillaries adjacent to the epithelial diaphragm.
d- Dental sac capillaries adjacent to the outer dental epithelium.
D
Enamel spindles are formed by:
a- Odontoblastic process.
b- Ameloblastic process.
c- Hypocalcified rods.
d- Cracks.
A
Neonatal lines are found in all the following except:
a- Enamel of primary incisors.
b- Enamel of permanent first molar.
c- Enamel of permanent second molars.
d- Enamel of primary molars.
C
Hypocalcified ectodermal structures in enamel are:
a- Spindles and lamellae.
b- Odontoblastic processes and tufts.
c- Tufts and spindles.
d- Lamellae type A,and tufts.
D
Which of the following most correctly describes the significance of Hunter Schreger bands?
a- It indicates variation in size of enamel rods.
b- It reflects variations in the length of enamel rods.
c- It represents hypercalcified areas in cervical enamel.
d- It is an optical effect that is not related to variations in enamel structure.
D
The orientation of hydroxyapatite crystals in enamel, the greatest crystal density would be present in:
a- enamel lamellae.
b- The interrod region.
c- The prismless layer.
d- Gnarled enamel.
C
Perikymata:
a- Are oriented parallel to the long axis of the crown (tooth).
b- Are surface manifestation of Retzius lines.
c- Are only located in prismless enamel.
d- Produce the scalloping seen along the DEJ.
B
Unmineralized structures seen in the enamel are :
a- Cross striations.
b- Enamel tufts.
c- Incremental lines of Retzius.
d- Enamel spindles.
D
All of the following statements about the incremental lines of Retzius in enamel are true except:
a- They run as concentric lines over the cusp.
b- Perikymata are outer manifestations of it.
c- They are formed as result of rhythmic apposition.
d- They do not reach the cervical region
D
Incremental lines of Retzius appear:
a- In dentin.
b- In enamel.
c- In cementum.
d- In bone.
B
