All Free Oral Histology MCQs with Answers

• A. Mainly by odontoblasts
• B. Only by ameloblasts
• C. Only on odontoblasts
• D. Mainly by ameloblasts

Explanation: Enamel matrix is produced and laid down exclusively by ameloblasts, whereas odontoblasts form dentin.

• A. Presence of high percentage of organic matrix
• B. Presence of incremental lines
• C. Most of organic component is lost during mineralization
• D. Enamel has high reparative capacity

Explanation: Enamel is distinctive because most of its organic matrix is removed during mineralization, leaving it highly mineralized.

• A. Hypoplasia of local origin
• B. None of the above
• C. Hypoplasia of hereditary origin
• D. Hypoplasia of systemic origin

Explanation: Chronological hypoplasia results from a systemic disturbance affecting ameloblasts during a particular period, so the defect follows a…

• A. Scalloped and the convexities are directed towards dentin
• B. Straight
• C. Non-scalloped
• D. Scalloped and the convexities are directed towards enamel

Explanation: The dentinoenamel junction is scalloped, with its convexities directed toward dentin, allowing enamel and dentin to interlock…

• A. All of the above
• B. They are almost vertical near the incisal edge (or) cusp tip areas
• C. In the cervical third of deciduous crowns they are almost horizontal in direction
• D. In cervical region of permanent teeth, they deviate in apical direction
• E. They originate at right angle to dentin surface

Explanation: Enamel rods generally begin approximately perpendicular to the dentin surface, become nearly vertical near cusps and incisal edges, and…

• A. 2 μ m
• B. 9 μ m
• C. 7 μ m
• D. 4 μ m

Explanation: An enamel rod is typically about 4 to 8 μm in diameter, with approximately 4 μm being the standard figure used in basic histology…

• A. 35%
• B. 50%
• C. 4%
• D. 96%

Explanation: Mature enamel contains approximately 96% inorganic mineral by weight, mainly hydroxyapatite, with only small organic and water fractions.

• A. Enamel matrix
• B. DEJ
• C. CEJ
• D. Root

Explanation: Enamel calcification begins at the dentinoenamel junction and progresses outward toward the surface.

• A. It has only a small percent of organic content
• B. Its formative cells are lost once it is completely formed
• C. It is essentially a keratin tissue and has no blood vessels
• D. It has no direct connection with the active cells of the dental pulp

Explanation: Ameloblasts form enamel but are lost after enamel formation is complete, so mature enamel cannot regenerate itself.

• A. Periodontal ligament
• B. Dentin
• C. Enamel
• D. Cementum

Explanation: Ameloblasts are the formative cells of enamel and disappear after enamel formation.

• A. None of the above
• B. Paddle appearance in cross section
• C. Lanullate appearance in cross-section
• D. Key hole appearance in cross section

Explanation: In cross-section, enamel rods commonly show a keyhole or paddle-like outline, with the head toward the incisal or occlusal surface.

• A. Constitute the rest lines with in the enamel rods
• B. Have high inorganic content
• C. They are areas of increased porosity
• D. Allow the movement of water and small ions

Explanation: Striae of Retzius are incremental, relatively hypomineralised lines that have increased porosity and can permit movement of water and…

• A. Does not take place once enamel surface and invironment
• B. Stops after 2 years of eruption
• C. Continues through out life
• D. Continues till adult life

Explanation: After eruption, enamel continues to exchange ions with saliva and the oral environment throughout life.

• A. Pulp
• B. Dentin
• C. Cementum
• D. Enamel

Explanation: The incremental growth lines called the striae of Retzius are characteristic of enamel.

• A. Enamel tufts
• B. Enamel lamella
• C. Incremental lines of enamel
• D. Enamel cuticle

Explanation: Enamel tufts are hypomineralised structures that arise at the dentinoenamel junction and extend inward, so they are not an external…

• A. Dark and light bands of enamel seen in horizontal ground section
• B. Dark and light bands of enamel seen in longitudinal ground section
• C. Dark and light brands of dentin seen in longitudinal section
• D. Dark and light bands of dentin seen in horizontal

Explanation: Hunter-Schreger bands are alternating dark and light bands produced by changes in the direction of enamel rod groups.

• A. 66%
• B. 76%
• C. 86%
• D. 96%

Explanation: Fully developed enamel is approximately 96% inorganic by weight, mainly hydroxyapatite, with only small organic and water components.

• A. Amelogenin
• B. Sheathlin
• C. Enamelin
• D. Tuftelin

Explanation: Amelogenin is the major non-acidic enamel matrix protein and helps regulate enamel crystal growth and mineralization.

• A. Same as dentin crystals
• B. Contains organic portion in the center
• C. Roughly texagonal in shape
• D. Their diameter is about 5 microns in size

Explanation: Enamel crystals are roughly hexagonal in cross-section, unlike the less regularly arranged crystals of dentin.

• A. Bone
• B. Gingiva
• C. Enamel
• D. Dentin

Explanation: Enamel is the most highly mineralized tissue in the body, so it contains the greatest proportion of phosphate among these choices.