ORE Part 1 Dental Anatomy and Histology — Questions and Answers
Question 1: Which permanent tooth has the longest root in the human dentition?
- Upper central incisor
- Upper canine (Correct answer)
- Lower first molar
- Upper first premolar
Correct answer: Upper canine
The maxillary canine has the longest root of any tooth in the human dentition. Its long, robust root provides excellent anchorage, which is why canines are often the last teeth to be lost in the ageing dentition and serve as important abutments in prosthodontics.
Question 2: What is the Tome's process associated with?
- Osteoblasts forming alveolar bone
- Ameloblasts secreting enamel matrix (Correct answer)
- Odontoblasts forming dentine
- Cementoblasts depositing cementum
Correct answer: Ameloblasts secreting enamel matrix
Tome's process is a cytoplasmic extension of the ameloblast cell that is responsible for secreting the enamel matrix during the secretory stage of amelogenesis. The shape and orientation of Tome's processes determine the characteristic rod and inter-rod pattern of mature enamel.
Question 3: How many root canals does a mandibular first molar typically have?
- Two
- Three (Correct answer)
- Four
- Five
Correct answer: Three
The mandibular first molar typically has two roots (mesial and distal) with three root canals — two in the mesial root (mesiobuccal and mesiolingual) and one in the distal root. However, a second distal canal is found in approximately 30% of cases, making four canals common.
Question 4: Which type of dentine is formed as a physiological response throughout life?
- Primary dentine
- Secondary dentine (Correct answer)
- Tertiary (reparative) dentine
- Mantle dentine
Correct answer: Secondary dentine
Secondary dentine is deposited slowly and continuously by odontoblasts throughout the life of a vital tooth, after root formation is complete. This gradually reduces the size of the pulp chamber. Tertiary dentine, by contrast, is formed as a pathological response to stimuli such as caries or attrition.
Question 5: The Hunter-Schreger bands seen in enamel are caused by which structural feature?
- Incremental lines of Retzius
- Changes in direction of enamel rod groups (Correct answer)
- Neonatal line
- Enamel tufts at the DEJ
Correct answer: Changes in direction of enamel rod groups
Hunter-Schreger bands are alternating light and dark bands seen in enamel under reflected light. They are caused by changes in direction (decussation) of groups of enamel rods, which creates zones that reflect light differently. This arrangement increases enamel's resistance to crack propagation.
Question 6: Which tooth is most commonly congenitally absent (excluding third molars)?
- Upper lateral incisor
- Lower second premolar (Correct answer)
- Lower central incisor
- Upper first premolar
Correct answer: Lower second premolar
The lower second premolar is the most commonly congenitally absent permanent tooth after the third molars. The upper lateral incisor is the second most commonly absent. Congenital absence (hypodontia) affects approximately 3–8% of the population for non-third-molar teeth.
ORE Part 1 Dental Anatomy and Histology
Which permanent tooth has the longest root in the human dentition?