ORE Part 1 Dental Anatomy and Histology 2 — Questions and Answers
Question 1: What is the primary mineral component of dental enamel?
- Calcium carbonate
- Hydroxyapatite (Correct answer)
- Fluorapatite
- Tricalcium phosphate
Correct answer: Hydroxyapatite
Dental enamel is composed of approximately 96% inorganic material by weight, primarily in the form of hydroxyapatite crystals (Ca10(PO4)6(OH)2). These crystals are organised into enamel rods, making enamel the hardest biological tissue in the human body.
Question 2: The cementoenamel junction (CEJ) shows three possible relationships. Which is the most common arrangement?
- Cementum overlaps enamel (Correct answer)
- Enamel overlaps cementum
- Cementum and enamel meet edge to edge
- A gap exists between cementum and enamel exposing dentine
Correct answer: Cementum overlaps enamel
In approximately 60% of teeth, cementum overlaps the enamel at the CEJ. In about 30%, they meet edge to edge, and in approximately 10%, there is a gap exposing the underlying dentine, which can contribute to cervical sensitivity.
Question 3: Which cells are responsible for forming cementum?
- Osteoblasts
- Ameloblasts
- Cementoblasts (Correct answer)
- Fibroblasts
Correct answer: Cementoblasts
Cementoblasts are the specialised cells responsible for forming cementum. They originate from the dental follicle (ectomesenchyme) and deposit cementum matrix on the root surface. Some cementoblasts become entrapped within the cementum they produce, becoming cementocytes.
Question 4: The dental papilla gives rise to which structure of the developed tooth?
- Enamel
- Dentine and pulp (Correct answer)
- Cementum
- Periodontal ligament
Correct answer: Dentine and pulp
The dental papilla is the ectomesenchymal condensation that forms the core of the developing tooth germ. It differentiates into odontoblasts (which form dentine) and the dental pulp. The dental follicle, in contrast, gives rise to cementum, periodontal ligament, and alveolar bone.
Question 5: Which permanent tooth is the first to erupt in the mouth?
- Lower central incisor
- Upper central incisor
- Lower first molar (Correct answer)
- Upper first molar
Correct answer: Lower first molar
The lower first permanent molar is typically the first permanent tooth to erupt, usually appearing at approximately 6 years of age. It erupts distal to the second deciduous molar and is often mistaken for a primary tooth by parents because no primary tooth is lost during its eruption.
Question 6: Interglobular dentine is found primarily in which part of the tooth?
- Within the pulp
- At the enamel surface
- In the crown dentine, just below the mantle dentine (Correct answer)
- In the cementum
Correct answer: In the crown dentine, just below the mantle dentine
Interglobular dentine consists of areas of unmineralised or hypomineralised dentine found in the crown, just beneath the mantle dentine layer. It results from failure of the calcospherites (globular masses of mineralisation) to fuse completely during dentinogenesis.
ORE Part 1 Dental Anatomy and Histology 2
What is the primary mineral component of dental enamel?