ORE Part 1 Dental Anatomy & Occlusion 3 — Questions and Answers
Question 1: Which ligament is the primary support structure of a tooth in its socket?
- Periodontal ligament (PDL) (Correct answer)
- Gingival ligament
- Circular ligament
- Dentoalveolar ligament
Correct answer: Periodontal ligament (PDL)
The periodontal ligament (PDL) is the fibrous connective tissue between the tooth root cementum and the alveolar bone proper. It provides support, proprioception, and nutrient supply to the alveolus.
Question 2: What is the 'contact area' of a tooth?
- The area where adjacent teeth contact each other proximally in the arch (Correct answer)
- The area of maximum occlusal contact
- The part of the tooth in contact with the tongue
- The area of gingival attachment
Correct answer: The area where adjacent teeth contact each other proximally in the arch
The proximal contact area is where adjacent teeth in the same arch touch. It prevents food impaction, maintains arch integrity, and protects the interdental papilla.
Question 3: What root configuration does the mandibular first molar typically have?
- Two roots (mesial and distal), mesial root has two canals (Correct answer)
- Two roots, each with a single canal
- Three roots: two buccal and one lingual
- One root with three canals
Correct answer: Two roots (mesial and distal), mesial root has two canals
The mandibular first molar typically has two roots: a mesial root (usually with two canals — mesiobuccal and mesiolingual) and a distal root (usually one or two canals).
Question 4: What is the 'tubercle of Zuckerkandl' (Carabelli cusp) and where is it found?
- An accessory cusp on the mesiopalatal cusp of the maxillary first molar (Correct answer)
- A root anomaly on the lower premolar
- A developmental pit on the upper central incisor
- An accessory root on lower canines
Correct answer: An accessory cusp on the mesiopalatal cusp of the maxillary first molar
The Cusp of Carabelli is a 5th (accessory) cusp found on the mesiopalatal surface of the maxillary first molar (occasionally second molar). It is more common in people of European descent.
Question 5: What is the 'terminal plane' in primary dentition and its significance for permanent molar eruption?
- The relationship between primary second molars distally — mesial step (ideal for Class I), flush terminal plane (may give Class I or II), or distal step (leads to Class II) (Correct answer)
- The position of the primary incisors in the arch
- The plane of primary molar occlusion
- The angle of primary canine eruption
Correct answer: The relationship between primary second molars distally — mesial step (ideal for Class I), flush terminal plane (may give Class I or II), or distal step (leads to Class II)
The terminal plane describes how the distal surfaces of the upper and lower primary second molars relate. A mesial step favours a Class I permanent molar relationship; a flush terminal plane may lead to Class I or Class II; a distal step typically leads to Class II.
Question 6: How many roots does the maxillary first premolar typically have?
- Two roots (buccal and palatal) — one of the few two-rooted premolars (Correct answer)
- One root only
- Three roots
- One root with two canals always
Correct answer: Two roots (buccal and palatal) — one of the few two-rooted premolars
The maxillary first premolar typically has two roots (buccal and palatal), making it anatomically distinct from the maxillary second premolar which more commonly has one root. Root canals correspond to each root.
ORE Part 1 Dental Anatomy & Occlusion 3
Which ligament is the primary support structure of a tooth in its socket?