EFDA Anatomy and Occlusion 4 — Questions and Answers
Question 1: Which muscle is the PRIMARY muscle responsible for closing the mandible (elevating)?
- Lateral pterygoid
- Digastric
- Masseter (Correct answer)
- Mylohyoid
Correct answer: Masseter
The masseter is the most powerful jaw-closing (elevator) muscle and is readily palpable on the lateral face during clenching.
Question 2: Identify the tooth surface facing the tongue on mandibular posterior teeth:
- Buccal
- Labial
- Lingual (Correct answer)
- Palatal
Correct answer: Lingual
The lingual surface of mandibular teeth faces the tongue; palatal is only used for maxillary teeth surfaces facing the palate.
Question 3: A patient presents with wear on the lingual surfaces of maxillary anterior teeth. This pattern is MOST associated with:
- Bruxism in a Class III occlusion
- Acid erosion from frequent vomiting or GERD (Correct answer)
- Heavy occlusal contacts on posterior teeth
- Abrasion from a hard toothbrush
Correct answer: Acid erosion from frequent vomiting or GERD
Palatal/lingual erosion of maxillary anterior teeth is a hallmark of acid erosion from intrinsic sources such as GERD or bulimia.
Question 4: The mandibular premolars differ from maxillary premolars in that they typically have:
- Two roots
- A prominent transverse ridge
- One root and one or two cusps (Correct answer)
- A larger buccal cusp than the lingual cusp
Correct answer: One root and one or two cusps
Mandibular premolars most often have a single root; the first mandibular premolar has a dominant buccal cusp with a small lingual cusp, while the second may have two lingual cusps.
Question 5: Which structure forms the posterior boundary of the hard palate?
- Vibrating line
- Pterygomandibular raphe
- Posterior nasal spine (Correct answer)
- Hamulus
Correct answer: Posterior nasal spine
The posterior nasal spine is the bony landmark that marks the posterior boundary of the hard palate where it meets the soft palate.
Question 6: In an ideal Class I occlusion, the mesiobuccal cusp of the maxillary first molar occludes in the:
- Distal fossa of the mandibular second premolar
- Buccal groove of the mandibular first molar (Correct answer)
- Central fossa of the mandibular first molar
- Mesial pit of the mandibular first molar
Correct answer: Buccal groove of the mandibular first molar
Angle's Class I key is that the mesiobuccal cusp of the maxillary first molar occludes in the buccal groove of the mandibular first molar.
Question 7: Which type of joint movement occurs at the temporomandibular joint during wide opening of the mouth?
- Rotation only
- Translation only
- Both rotation and translation (Correct answer)
- Lateral gliding only
Correct answer: Both rotation and translation
During wide opening, the TMJ first rotates (hinge movement) and then translates (condyle moves forward and downward along the articular eminence).
EFDA Anatomy and Occlusion 4
Which muscle is the PRIMARY muscle responsible for closing the mandible (elevating)?