MDS PREP
The nerve to masseter passes
1. deep to the medial pterygoid muscle
2. posterior to temporomandibular joint
3. superior to zygomatic arch to enter the muscle on its medial surface
4. through the mandibular notch to enter the muscle on its medial surface
Anatomy
Answer: 4
The nerve to masseter passes through the mandibular notch to enter the muscle on its medial surface
The nerve to the masseter muscle is the masseteric nerve, which is a branch
of the mandibular nerve (CN V3), the largest division of the trigeminal nerve
(cranial nerve V). The masseter muscle is one of the muscles of mastication that
lifts the lower jaw, contributing to the action of biting and chewing.
The masseteric nerve originates from the anterior division of the mandibular
nerve and typically passes:
1. Deep to the medial pterygoid muscle: The medial pterygoid muscle is located
in the infratemporal fossa, which is the space deep to the zygomatic arch and
medial to the temporomandibular joint (TMJ). The masseteric nerve runs in a deep
position relative to the medial pterygoid muscle as it travels towards the
masseter muscle. This muscle is involved in the side-to-side movement of the
jaw, known as lateral excursion.
2. Posterior to the temporomandibular joint: The TMJ is the articulation between
the mandible and the temporal bone of the skull. It is a synovial joint that
allows for the hinge movement of the jaw, such as opening and closing the mouth.
The masseteric nerve passes behind the TMJ to reach the masseter muscle. This
nerve does not actually cross the joint itself but runs in a position posterior
to it.
3. Superior to the zygomatic arch: The zygomatic arch is the bony structure that
extends from the zygomatic process of the temporal bone to the zygomatic bone of
the skull. It forms the prominence of the cheek. The masseteric nerve runs
superior to the zygomatic arch to reach the masseter muscle. The arch serves as
a landmark for the nerve's course, and the nerve typically does not pass through
the arch itself.
4. Through the mandibular notch: This statement is not entirely correct. The
masseteric nerve does not pass through the mandibular notch, which is a
depression on the medial surface of the ramus of the mandible, but rather it
passes above (superior to) the notch. The mandibular notch is the location where
the masseteric nerve and the other branches of the mandibular nerve leave the
infratemporal fossa and enter the submandibular space to innervate the muscles
of mastication, including the masseter. The nerve then runs along the lateral
surface of the lateral pterygoid plate and enters the deep surface of the
masseter muscle.
In summary, the masseteric nerve passes deep to the medial pterygoid muscle,
posterior to the TMJ, and superior to the zygomatic arch. It does not pass
through the mandibular notch; instead, it runs superior to it before reaching
the masseter muscle. The anatomical pathway of this nerve allows it to
effectively innervate the masseter muscle, which is crucial for the function of
the muscle in mastication.
The largest and longest root canal of the maxillary second molar is the
1. lingual
2. mesiobuccal
3. distobuccal
4. distal
Dental Anatomy
Answer: 1
The largest and longest root canal of the maxillary second molar is the lingual
Immediately following the closure of the A-V valves is the period of
1. Isotonic contraction
2. Isometric contraction
3. Isometric relaxation
4. Isotonic relaxation
Anatomy
Answer: 3
Immediately following the closure of the A-V valves is the period of
Isometric relaxation
The canine eminence is
1. associated with the mandibular canine only
2. the labial ridge on the crown of canine
3. an osseous structure surrounding the root of a canine on the facial aspect
4. the prominent ridge on the lingual surface of a maxillary canine
Dental Anatomy Answer: 3
The canine eminence is
an osseous structure surrounding the root of a canine on the facial aspect
If a 4th root canal is present in a maxillary 1st molar, it will likely be located in which of the following roots?
1) Mesiolingual
2) Mesiobuccal
3) Distolingual
4) Distofacial
Dental Anatomy Answer: 2
Well over 50% of maxillary 1st molars have two canals in the mesiobuccal root. Some authors cite the number as high as 90%.
There are usually 3 roots and 4 canals in a maxillary 1st molar.
The fourth canal, the mesiolingual canal, is also referred to as: the accessory mesiobuccal canal, mesiocentric, mesiopalatal canal or MB2.
It is usually tough to find MB2 through clinical inspection and it is not obvious on a radiograph. A dentist should expect it is present before beginning a root canal on the first maxillary molar.
The first bone to Ossify in the body is
1. Mandible 2 Maxilla
3. Clavicle 4. Calvarium
Anatomy
Answer: 3
Clavicle is the first bone to Ossify in the body
When extracting a primary maxillary incisor in which the root has been partially resorbed because of pres sure from its developing succe daneous tooth, which aspect of the remaining primary root will usually be longest and attached most securely to the gingiva?
1. Facial
2. Mesial
3. Lingual
4. Distal
Dental Anatomy
Answer: 1
In the case of primary teeth, the roots are often resorbed as the permanent teeth develop. The facial aspect of the root tends to be the last area to undergo resorption due to its position and the way the succedaneous tooth exerts pressure. The facial root surface is generally more stable and remains attached to the gingiva longer than the other aspects, making it the longest and most securely attached during extraction.
The beginning of active eruption of a human tooth occurs
1. before the root has begun to develop
2. coincidental with the beginning of root formation
3. before the root has begun to develop
4. after one half of the root is formed
Dental Anatomy
Answer: 4
The beginning of active eruption of a human tooth occurs after one half of the root is formed