MCQs in Oral Histology

Chapter 5: Enamel

 

1- Ameloblasts having ruffled borders are:     

  1. Secretory ameloblasts.
  2. Maturative ameloblasts.
  3. Protective ameloblasts.
  4. Transitional ameloblasts.

 

 

 

 

 

 

 

The answer is: B

 

2-Which of the following is not a feature of enamel?

  1. Contour lines of Owen.
  2. Cross striations.
  3. Prism sheath.
  4. Perikymata.

 

 

 

 

 

 

 

The answer is: A

 

3-Maturative ameloblasts are characterized by having:

  1. A distally positioned nucleus.
  2. A highly basophilic cytoplasm.
  3. A highly-developed Golgi complex.
  4. A distal cell membrane with many infoldings.

 

 

 

 

 

 

The answer is: D

 

4- Which of the following does not occur during maturation of enamel?

  1. Influx of calcium and phosphorus.
  2. Growth of hydroxyapatite crystals.
  3. Increase in organic content.
  4. Decrease in the water content.

 

 

 

 

 

 

 

The answer is: C

 

5- Incremental lines are a result of variation in:

  1. Proliferation
  2. Histodifferentiation
  3. Morphodifferentiation
  4. Rhythmic apposition

 

 

 

 

 

 

 

The answer is: D

 

6- The prismatic structure of enamel is due to:

  1. Variation in the density of organic material.
  2. Variation in crystal orientation.
  3. A rhythmic pattern of apposition.
  4. The periodic change in prism direction.

 

 

 

 

 

 

 

The answer is: B

 

7- The prismless layer of enamel:

  1. Is found only in primary teeth.
  2. Does not contain prism & prism sheaths.
  3. Is found near the amelo-dentinal junction.
  4. Contains no hydroxyapatite.

 

 

 

 

 

 

The answer is: B

 

8- Enamel tufts:

  1. Contain cellular processes.
  2. Can pass to dentin.
  3. Are seen in decalcified sections.
  4. Are grass like structure.

 

 

 

 

 

 

The answer is: D

 

9- During the maturation stage of enamel formation, which of the following does not occur in the ameloblastic layer?

  1. Water absorption.
  2. Protein absorption.
  3. Change in cellular organelles.
  4. Secretion of enamel matrix.

 

 

 

 

 

 

The answer is: D

 

10- When prismless enamel is formed, the secretory ameloblast does notcontain: 

  1. Rough endoplasmic reticulum.
  2. Tome's process.
  3. Nucleus.
  4. Secretory granules.

 

 

 

 

 

 

 

The answer is: B

 

11- Which of the following is true:

  1. Enamel is the weakly mineralized tissue.
  2. Enamel is the highly mineralized tissue.
  3. Enamel is the highly permeable tissue.
  4. Enamel is a non brittle tissue.

 

 

 

 

 

 

 

The answer is: B

 

12- Neonatal lines are present in:

  1. All permanent teeth.
  2. Permanent canines.
  3. All deciduous & first permanent molar.
  4. Premolars.

 

 

 

 

 

 

 

The answer is: C

 

13- Organic components of enamel are primarily removed from enamel by:

  1. Secretory ameloblasts.
  2. Maturative ameloblasts.
  3. Transitional ameloblasts.
  4. Enamel spindle.

 

 

 

 

 

 

 

The answer is: B

 

14- The main difference between the rod and the interrod region is:

  1. Crystal size.
  2. Crystal orientation.
  3. Crystal composition.
  4. In the nature of the organic component.

 

 

 

 

 

 

 

 The answer is: B

 

15- The striae of Retzius:

  1. Are parallel to the enamel rods.
  2. Are parallel to the surface of the enamel in the cervical region.
  3. Are not seen in the cuspal one third of the enamel.
  4. Would be seen as concentric rings in a horizontal section of the crown.

 

 

 

 

 

 

 

The answer is: D

 

16-Enamel is composed of: 

  1. Rod, interrod & rod sheath.
  2. Only enamel prisms.        
  3. Needle shaped crystals.
  4. Prism sheath.

 

 

 

 

 

 

 

The answer is: A

 

17-The extensions from secretory ameloblast cells that give structure to enamel rods are called:

  1. Enamel tuft.                                          
  2. Tomes processes.
  3. Enamel spindles.                         
  4. Enamel lamellae.

 

 

 

 

 

 

 

The answer is: B

 

18- Striae of Retzius: 

  1. Result from enamel crack.                     
  2. Separate prenatal from postnatal enamel.
  3. Are due to rhythmic apposition of enamel.                                               
  4. Are hypermineralized structure.

 

 

 

 

 

 

 

The answer is: C

 

19- Enamel Rods: 

  1. Their number varies in different teeth.
  2. Have an average width of 1um.
  3. Are Present at the enamel surface.
  4. Have a straight course at the cusps of teeth.

 

 

 

 

 

 

The answer is: A

 

20- Enamel is formed of:

  1. 76% minerals & 24% organic materials and water.
  2. 96% minerals & 4% organic materials and water.
  3. 86% minerals & 14% organic materials and water.
  4. 99% minerals & 1% organic materials and water.

 

 

 

 

 

 

The answer is: B

 

21- which of the following is absent in all premolars:

  1. Enamel spindle.
  2. Enamel tuft.
  3. Neonatal line.
  4. Enamel lamella.

 

 

 

 

 

 

 

 The answer is: C

 

 

22- Cross striations in enamel:

  1. Are an optical phenomena.
  2. Result from abrupt change in environment before and after birth.
  3. Result from mineralization disorder.
  4. Appear to be periodic bands at 4 microns interval across the rod.

 

 

 

 

 

 

 

The answer is: D

 

23- The prism sheath:

  1. Is a dense continuous sheath separating rod from inter-rod.
  2. Result from abrupt change in crystals orientation.
  3. Is more mineralized than rod and inter-rod.
  4. Found in prismless enamel.

 

 

 

 

 

 

 

The answer is: B

 

24- The complex arrangement of rods over the cusps of teeth is termed: 

  1. Prismless enamel.
  2. Gnarled enamel.
  3. Prenatal enamel.
  4. Postnatal enamel.

 

 

 

 

 

 

 

The answer is: B

 

25- The origin of enamel is:

  1. neural crest cells
  2. Ectoderm
  3. Mesoderm
  4. Ectomesenchyme

 

 

 

 

 

 

 

The answer is: B

 

26- Hypocalcified areas in enamel are:

  1. Enamel spindles.
  2. Dentino-enamel junction.
  3. Interprismatic substances.
  4. Enamel tufts.

 

 

 

 

 

 

The answer is: D

 

27- Prismless enamel:

  1. Is less mineralized than prismatic enamel.
  2. Is found only in the cervical area of permanent teeth.
  3. Is harder than prismatic enamel.
  4. Found near the dentino-enamel junction.

 

 

 

 

 

 

The answer is: C

 

28- The perikymata: 

  1. Is an optical phenomena resulting from changes in direction of enamel rods. 
  2. Is a highly mineralized outer enamel surface.
  3. Is formed of transverse grooves, represents an outer manifestation of brown stria of Retzius.
  4. Found at the cusp tip.

 

 

 

 

 

 

 The answer is: C

 

29- What is the result of cracks before tooth eruption:

  1. Enamel lamella type A.
  2. Enamel lamella type B.
  3. Enamel lamella type C.
  4. Enamel tufts.

 

 

 

 

 

 

 

The answer is: B

                                           

30- The primary enamel cuticle is formed by the: 

  1. Outer dental epithelium.
  2. Ameloblasts just before tooth eruption.
  3. Fusion of oral epithelium and reduced enamel epithelium.
  4. Ameloblasts after the enamel has been completed.

 

 

 

 

 

 

The answer is: D

 

31- The surface enamel:

  1. Is similar to the subsurface enamel.
  2. Is softer than subsurface enamel.
  3. Contains less mineral than subsurface enamel.
  4. Highly mineralized than subssurface enamel.

 

 

 

 

 

 

 

The answer is: D

 

32- The prism sheath:

  1. Is a continuous sheath.
  2. Is more calcified than the enamel rod.
  3. Is less calcified than the enamel rod.
  4. Is equally calcified when compared to the enamel rod. 

 

 

 

 

 

 

 

The answer is: C

 

33- The predominant inorganic portion of enamel is:

  1. Calcium
  2. Carbonate
  3. Phosphate
  4. Fluoride

 

 

 

 

 

 

 

The answer is: A

 

34- Incremental lines of Retzius form grooves on the surface of the enamel  termed:

  1. Perikymata.
  2. Neonatal lines.
  3. Gnarled enamel.
  4. Enamel cuticle.

 

 

 

 

 

 

 

The answer is: A

 

35- Which of the following is poorly calcified enamel?

  1. Gnarled enamel.
  2. True enamel lamellae.
  3. Perikymata and gnarled enamel.
  4. Interprismatic substance.

 

 

 

 

 

 

 

 

 The answer is: B

 

36- The cross striations characteristic of enamel rods represent:

  1. Incremental growth pattern.
  2. The junctional complex of ameloblasts.
  3. Hunter-Schreger bands.
  4. The inter rod region.  

 

 

 

 

 

 

 

The answer is: A

 

37- Enamel spindles:

  1. Are areas of prismatic enamel.
  2. Are present at the occlusal surfaces of enamel.
  3. Are the terminal ends of odontoblastic processes.
  4. Are located at the cemento-enamel junction. 

 

 

 

 

 

 

The answer is: C

 

38- Which of the following is a true statement about the organic matrix of the newly synthesized enamel?

  1. It represents 30% by weight of the organic content.
  2. It has a high content of amelogenins.
  3. It contains collagen fibers.
  4. It has a high inorganic content.

 

 

 

 

 

 

 

The answer is: B

 

39- Which of the following is the source of nutrient supply to the secretory ameloblasts during early crown formation?

  1. Subodontoblastic plexus of capillaries.
  2. Central blood vessels in the dental papilla.
  3. Dental sac capillaries adjacent to the epithelial diaphragm.
  4. Dental sac capillaries adjacent to the outer dental epithelium.

 

 

 

 

 

 

 

The answer is: D

 

40- Tome's processes:

  1. Contain mitochondria, but lack Golgi saccules and rough endoplasmic reticulum.
  2. Lack secretory granules.
  3. Indent the immature enamel to produce a serrated outline on its appositional surface.
  4. Are located at the proximal end of the ameloblast.

 

 

 

 

 

 

 

The answer is: C

 

41- Enamel spindles are formed by:

  1. Odontoblastic process. 
  2. Ameloblastic process.
  3. Hypocalcified rods.
  4. Cracks.

 

 

 

 

 

 

 

The answer is: A

 

42- Neonatal lines are found in all the following except:

  1. Enamel of primary incisors.
  2. Enamel of permanent first molar.
  3. Enamel of permanent second molars.
  4. Enamel of primary molars.

 

 

 

 

 

 

 

The answer is: C

 

43- Hypocalcified ectodermal structures in enamel are:

  1. Spindles and lamellae.
  2. Odontoblastic processes and tufts.
  3. Tufts and spindles.
  4. Lamellae type A,and tufts. 

 

 

 

 

 

 

 

The answer is: D

 

44- Which of the following most correctly describes the significance of Hunter Schreger bands?

  1. It indicates variation in size of enamel rods.
  2. It reflects variations in the length of enamel rods.
  3. It represents  hypercalcified areas in cervical enamel.
  4. It is an optical effect that is not related to variations in enamel structure.

 

 

 

 

 

 

 

The answer is: D

 

45- The orientation of hydroxyapatite crystals in enamel, the greatest crystal density would be present in:

  1. enamel lamellae.
  2. The interrod region.
  3. The prismless layer.
  4. Gnarled enamel.

 

 

 

 

 

 

 

The answer is: C

 

46- Perikymata:

  1. Are oriented parallel to the long axis of the crown (tooth).
  2. Are surface  manifestation of Retzius lines.
  3. Are only located in prismless enamel.
  4. Produce the scalloping seen along the DEJ.

 

 

 

 

 

 

The answer is: B

 

47- Unmineralized structures seen in the enamel are :

  1. Cross striations.
  2. Enamel tufts.
  3. Incremental lines of Retzius.
  4. Enamel spindles. 

 

 

 

 

 

 

 

The answer is: D

 

48- All of the following statements about the incremental lines of Retzius in enamel are true except:

  1. They run as concentric lines over the cusp.
  2. Perikymata are outer manifestations of it.
  3. They are formed as result of rhythmic apposition.
  4. They do not reach the cervical region. 

 

 

 

 

 

 

 

The answer is: D

 

49-Incremental lines of Retzius appear:

  1. In dentin.
  2. In enamel.
  3. In cementum.
  4. In bone.

 

 

 

 

 

 

 

The answer is: B

 

50-Primary enamel cuticle is:

  1. Afibrillar cementum.
  2. Precipitate of salivary proteins.
  3. Relatively structureless layer of enamel.
  4. A last product of ameloblasts.

 

 

 

 

 

 

 

The answer is: D

 

51- Hunter-Schreger bands have all the following characteristics except:

  1. They are best seen in reflected light.
  2. They are alternating dark and light bands
  3. They are most likely an optical phenomenon
  4. They are found at the cusp tip.

 

 

 

 

 

 

The answer is: D

 

52- Enamel tufts and enamel lamellae resemble each other in that both:

  1. Are formed prior to tooth eruption only.
  2. Extend over full thickness of the enamel.
  3. Are hypermineralized structures.
  4. Are hypomineralized structures.

 

 

 

 

 

 

The answer is: D

 

53-Enamel is by weight:

  1. 70% mineral, 26% organic matrix, 4% water.
  2. 76% mineral, 20% organic matrix, 4% water.
  3. 25% mineral, 12% organic matrix, 3% water.
  4. 95% mineral, 1% organic matrix, 4% water.

 

 

 

 

 

 

 

The answer is: D

 

54- All of the following structures in enamel are ectodermal origin except:

  1. Enamel spindle.
  2. Enamel prisms.
  3. Enamel lamellae (type A).
  4. Enamel tufts. 

 

 

 

 

 

 

 

The answer is: A

 

55- Enamel is:

  1. An ectodermal tissue covering the anatomical crown.
  2. A mesodermal tissue covering the crown.
  3. An endodermal tissue.
  4. A mesenchymal tissue.

 

 

 

 

 

 

 

The answer is: A

 

56- Gnarled enamel has the following criteria except:

  1. Found under cusp tips and incisal ridges.
  2. The course of the enamel rods is more straighter.
  3. The enamel rods become twisted and braided.
  4. Found to give maximum strength to the areas subjected more to the masticatory forces.

 

 

 

 

 

 

 

The answer is: B

 

57- The peripheral part of the E rod is called:

  1. Interrod region.                   
  2. Rod sheath.
  3. Rod region.                         
  4. Key hole.

 

 

 

 

 

 

 

The answer is: B

 

 

58- Concerning the rod sheath, one of the following statement isincorrect:

  1. It occupies the peripheral part of the E. rod.
  2. It forms the border where crystals of the rod and interrod enamel meet.
  3. It is highly calcified than the rod.
  4. It has a higher organic content thus resists decalcification more than the rod.

 

 

 

 

 

 

 

 

The answer is: C

 

59- The interrod enamel is:

  1. More calcified than the E. rod.
  2. Less calcified than the E. rod.
  3. The same calcification as the E. rod.
  4. Organic in nature.

 

 

 

 

 

 

 

The answer is: C

 

60- Cross striations or short increments:

  1. Represent the rhythmic apposition of the E. matrix by ameloblasts.
  2. Represent alternating constriction and expansion of E. rods at and in-between the striations.
  3. Represent the daily rate of secretory activity of the ameloblast.
  4. All of the above.                 

 

 

 

 

 

 

 

The answer is: D

 

61- The formation of the enamel matrix between two short increments needs:

  1. One day.                      
  2. Two days.
  3. Three drays.             
  4. Four days.

 

 

 

 

 

 

 

The answer is: A

 

62- Neonatal line is all the following except :

  1. Is one of the brown striae of Retzius that gets accentuated.
  2. Is present in deciduous teeth and all permanent molars.
  3. Separates enamel formed before birth from that formed after birth.
  4. It is due to abrupt change in nutrition and environmental condition at birth.

 

 

 

 

 

 

 

The answer is: B

 

63- The quality of the prenatal Enamel:

  1. Is better than that of the postnatal E.
  2. Is not as better as that of the postnatal E.
  3. Is equal to the quality of postnatal E.
  4. Not related to the quality of postnatal E.

 

 

 

 

 

 

The answer is: A

 

 

64- The dentinoenamel junction (DEJ)  :

  1. Appears to be scalloped with convexities of the scallops directed to E.
  2. Appears to be scalloped with convexities of the scallops directed to D.
  3. Appears to be scalloped with convexities of the scallops directed to cementum.
  4. None of the above.

 

 

 

 

 

 

 

 The answer is: B

 

65- The firm attachment between E and D is due to:

  1. Under cuts created by the scallops of the DEJ.
  2. Interdigitation at the DEJ between fibrils of first formed layer of D and that of first formed layer of E.
  3. Interdigitation between the hydroxyapatite crystals that are deposited during mineralization of E and D.
  4. All of the above.                 

 

 

 

 

 

 

 

The answer is: D

 

66- E. lamellae are all the following except :

  1. Thin leaf or sheet like structures.
  2. Extend from the E surface and may extend to D.
  3. Demonstrated in the longitudinal ground section only.
  4. Hypo or unmineralized structures

 

 

 

 

 

 

 

The answer is: C

 

67- Enamel spindles:

  1. They are odontoblastic cell bodies pass across the DEJ into the E.
  2. They are extended between the preameloblasts after enamel is formed.
  3. They are most common beneath cusps.
  4. They are best demonstrated in longitudinal decalcified section.

 

 

 

 

 

 

 

The answer is: C

 

68- Rodless Enamel:

  1. Occurs in the outermost 70 microns of the E.
  2. Their crystals are aligned at right angel to the surface
  3. Found most common  at the cervical areas of E surface.
  4. All of the above.

 

 

 

 

 

 

 

The answer is: D

 

69- Perikymata are:

  1. Vertically oriented wave like grooves.
  2. The external manifestation of the brown striae of Retzius.
  3. Numerous at the incisal or cusp regions.
  4. Parallel to the AEJ

 

 

 

 

 

 

 

The answer is: B

 

 

70- Which of the following tissues begins formation first:

  1. Enamel                                
  2. Dentin
  3. Pulp                                      
  4. Cementum

 

 

 

 

 

 

 

The answer is: B

 

71- Attrition is characterized by:

  1. Being a condition of normal wear of the occlusal      and proximal surfaces.
  2. A chemical loss of occlusal tooth structure, but not from dental caries.
  3. A loss of crown structure on the occlusal surface by mechanical means.
  4. None of the above.

 

 

 

The answer is: A

 

72- In mature dental tissues, the only tissue whose cells are lost is:

  1. Dentin                                                   
  2. Enamel
  3. Cementum                                                       
  4. Pulp

 

 

 

 

 

The answer is: B

 

 

73- Incremental lines of Retzius appear:

  1. In dentin and follow the appositional pattern.
  2. In enamel and follow the appositional pattern.
  3. In cementum and follow the appositional pattern.
  4. As lines in E running at right angles to the E surface.

 

 

 

 

 

 

The answer is: B

 

74- Enamel is by weight:

  1. 88-90 % mineral, 10-12 % organic matrix and water.
  2. 76% mineral, 20% organic matrix, 4 water.
  3. 25% mineral, 12% organic matrix, 3% water.
  4. 96% mineral, 1-2% organic material, 2-3% water.

 

 

 

 

 

 

 

The answer is: D

 

75- Which of the following is not true about Enamel rod ?

  1. They run from the dentinoenamel junction to the crown surface.
  2. Length of all enamel rods is equal.
  3. They are the basic structural units of E.
  4. They may be hexagonal ,rounded, oval or keyhole shape in cross section.

 

 

 

 

 

 

 

The answer is: B

 

 

76- Which of the following statements about E . is false?

  1. The heads of enamel rods are directed cervically, the tails occlusally.
  2. Rod sheaths are relatively hypocalcified areas surrounding the rods.
  3. Human E rods in cross section have an outline similar to a keyhole.
  4. Hydroxyapatite crystals run parallel to the long axis of the rods and perpendicular to it in the interrod region .

 

 

 

 

 

 

The answer is: A

 

77- It is particularly difficult to finish the wall of a cavity preparation in cuspal enamel because of the presence in that area of:

  1. Tufts                            
  2. Horizontal E. rods
  3. Gnarled E                      
  4. Spindles

 

 

 

 

 

 

 

The answer is: C

 

78- Enamel tufts and Enamel lamella resemble each other, in that both:

  1. Are formed after to tooth eruption.
  2. Extend over full thickness of the enamel.
  3. Are hypermineralized structures.
  4. Are oriented in a vertical direction perpendicular on the DEJ.

 

 

 

 

 

 

 

 

The answer is: D

 

79- All of the following statements about the incremental lines of Retzius in Enamel are true except:

  1. In a longitudinal section they run obliquely, relative to D.E.J.
  2. Perikymata in newly erupted teeth are manifestations of the lines of Retzius.
  3. They are formed as a result of rhythmic variations in the calcification.
  4. Under no conditions can a line of Retzius to be a neonatal line.

 

 

 

 

 

 

 

 The answer is: D

 

80- Enamel has no possibility of self-repair because:

  1. It has a small percentage of organic content.
  2. Its formative cells are lost once it is fully formed and the tooth erupted.
  3. It is essentially a keratin tissue and has no blood vessels.
  4. It has no direct connection with the active cells of the pulp tissue.

 

 

 

 

 

 

 

 

The answer is: B