ORE Part 1 Dental Anatomy & Occlusion 5

Question 1

What anatomical structure separates the anterior and posterior cranial fossae?

Accepted Answer

The lesser wing of the sphenoid and the petrous part of the temporal bone (forming the floor boundaries)

Answer

The boundary between the anterior and middle cranial fossae is formed by the lesser wing of the sphenoid and the anterior clinoid processes. This is relevant in dental anatomy when understanding skull base relationships.

Question 2

What is the 'leeway space' in mixed dentition?

Accepted Answer

The size difference between primary canine and molars versus their permanent successors (premolars and canine) — typically 1.5 mm in maxilla and 2.5 mm in mandible

Answer

Leeway space is the additional space from the fact that primary canines and molars are wider mesiodistally than their permanent successors (canine + premolars). It is used to accommodate the permanent canines and correct minor crowding.

Question 3

Which movement of the TMJ is described as the 'hinge movement'?

Accepted Answer

Pure rotation of the condyle around a transverse axis in the lower joint compartment (inferior joint space)

Answer

The hinge (rotational) movement of the mandible occurs in the inferior compartment of the TMJ, with the condyle rotating around a transverse axis. Pure rotation allows approximately 20–25 mm of mouth opening.

Question 4

What is the 'Frankfort plane' and what is it used for in orthodontic assessment?

Accepted Answer

A horizontal reference plane from the inferior margin of the orbit (orbitale) to the tragus/superior margin of the external auditory meatus — used as a standard reference in cephalometric analysis

Answer

The Frankfort Horizontal plane is defined by the infraorbital rim and porion (external auditory meatus). It represents the natural head position and is a key reference plane in lateral cephalometric radiograph analysis.

Question 5

What is the average root length of the maxillary central incisor?

Accepted Answer

Approximately 13 mm

Answer

The maxillary central incisor has a crown length of approximately 10–11 mm and a root length of approximately 13 mm, giving a total tooth length of approximately 23 mm on average.

ORE Part 1 Practice Test

ORE Part 1 Practice Test

ORE Part 1 Dental Anatomy & Occlusion 5