MJDF Dental Anatomy & Physiology 4 — Questions and Answers
Question 1: What is the term for the junction between enamel and cementum on the tooth surface?
- Cemento-enamel junction (CEJ) (Correct answer)
- Dentoenamel junction (DEJ)
- Gingival margin
- Periodontal junction
Correct answer: Cemento-enamel junction (CEJ)
The cemento-enamel junction (CEJ) marks the boundary between the enamel-covered crown and the cementum-covered root, serving as a critical clinical reference for attachment level measurements.
Question 2: What is the approximate percentage of inorganic content in mature enamel?
- 96% (Correct answer)
- 70%
- 50%
- 80%
Correct answer: 96%
Mature enamel is approximately 96% inorganic (hydroxyapatite crystals), making it the hardest and most mineralised tissue in the human body, with only about 1% organic matrix and 3% water.
Question 3: Which region of the pulp contains the highest density of nerve endings?
- Sub-odontoblastic plexus of Raschkow (Correct answer)
- Central pulp core
- Pulp horn apex
- Radicular pulp
Correct answer: Sub-odontoblastic plexus of Raschkow
The plexus of Raschkow, located just below the odontoblast layer in the coronal pulp, contains a dense network of unmyelinated C-fibres and myelinated Aδ fibres responsible for pain perception.
Question 4: What is the biological mechanism by which dentine hypersensitivity is explained by the hydrodynamic theory?
- Fluid movement in dentinal tubules triggers mechanoreceptors at the pulp-dentine boundary (Correct answer)
- Direct nerve stimulation through exposed dentine
- Acid directly attacking nerve endings
- Chemical diffusion through enamel
Correct answer: Fluid movement in dentinal tubules triggers mechanoreceptors at the pulp-dentine boundary
Brannstrom's hydrodynamic theory proposes that stimuli (cold, touch, osmosis) cause rapid dentinal fluid movement, which activates Aδ fibres at the pulp-dentine boundary, producing a sharp pain response.
Question 5: How does secondary dentine differ from tertiary (reactionary) dentine?
- Secondary forms throughout life at a slow rate; tertiary forms rapidly in response to injury (Correct answer)
- They are identical
- Tertiary forms throughout life; secondary forms in response to injury
- Secondary only forms in primary teeth
Correct answer: Secondary forms throughout life at a slow rate; tertiary forms rapidly in response to injury
Secondary dentine deposits slowly throughout life, reducing pulp chamber volume; tertiary (reactionary or reparative) dentine forms rapidly in response to caries, attrition, or restorative procedures.
Question 6: Which structure is responsible for tooth eruption according to the most widely accepted theory?
- PDL traction forces and alveolar bone remodelling (Correct answer)
- Enamel organ pushing the tooth upward
- Root elongation alone
- Hydraulic pressure in the pulp
Correct answer: PDL traction forces and alveolar bone remodelling
The most accepted eruption theory involves PDL fibre traction and coordinated alveolar bone resorption coronally and deposition apically, driving the tooth towards the occlusal plane.
MJDF Dental Anatomy & Physiology 4
What is the term for the junction between enamel and cementum on the tooth surface?