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NBDE Part I study materials
NBDE Part I study resources

NBDE Part I practice questions

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Question 1Anatomic Sciences

Which nerve supplies the muscles of mastication?

  1. Hypoglossal nerve (XII)
  2. Maxillary nerve (V2)
  3. Facial nerve (VII)
  4. Mandibular nerve (V3) Correct answer.

Explanation

The mandibular division of the trigeminal nerve carries motor fibers to the four muscles of mastication (masseter, temporalis, medial pterygoid, lateral pterygoid) as well as to the mylohyoid and anterior digastric. The maxillary division is purely sensory, and the facial and hypoglossal nerves supply muscles of facial expression and tongue musculature, respectively.

Question 2Anatomic Sciences

How many roots does a typical maxillary first molar have?

  1. Four
  2. Three Correct answer.
  3. Two
  4. One

Explanation

The maxillary first molar normally has three roots: a large palatal root and two buccal roots (mesiobuccal and distobuccal). Mandibular molars typically have two roots, and premolars usually have one or two.

Question 3Anatomic Sciences

Enamel consists predominantly of which material?

  1. Hydroxyapatite Correct answer.
  2. Keratin
  3. Collagen
  4. Elastin

Explanation

Mature enamel is roughly 96% mineral by weight, chiefly calcium phosphate crystallized as hydroxyapatite. Its organic content is minimal and consists of non-collagenous proteins rather than collagen, keratin, or elastin.

Question 4Anatomic Sciences

The articular disc of the temporomandibular joint is composed of which tissue?

  1. Synovial tissue
  2. Fibrocartilage Correct answer.
  3. Hyaline cartilage
  4. Elastic cartilage

Explanation

The TMJ disc is a dense fibrous structure of fibrocartilage, which withstands compressive and shear loads better than hyaline cartilage in this location. Hyaline cartilage covers the articular surfaces of most synovial joints but not the TMJ.

Question 5Anatomic Sciences

Which lingual papillae normally lack taste buds?

  1. Filiform Correct answer.
  2. Circumvallate
  3. Foliate
  4. Fungiform

Explanation

Filiform papillae are the most numerous lingual papillae and serve a mechanical, abrasive function; they carry no taste buds. Fungiform, circumvallate, and foliate papillae all contain taste buds.

Question 6Anatomic Sciences

Which region is covered by keratinized oral mucosa?

  1. Ventral tongue
  2. Floor of the mouth
  3. Hard palate Correct answer.
  4. Buccal mucosa

Explanation

The hard palate, together with the attached gingiva, is lined by masticatory mucosa, which is orthokeratinized or parakeratinized to resist friction during mastication. Lining mucosa elsewhere is generally nonkeratinized.

Question 7Anatomic Sciences

Taste from the anterior two-thirds of the tongue is carried by which nerve?

  1. Glossopharyngeal nerve
  2. Vagus nerve
  3. Trigeminal nerve
  4. Facial nerve Correct answer.

Explanation

Taste buds of the anterior two-thirds of the tongue are supplied by the chorda tympani, a branch of the facial nerve, which joins the lingual nerve in the infratemporal fossa. General sensation from the same region travels with the trigeminal nerve, not the facial nerve.

Question 8Anatomic Sciences

Which primary tooth usually erupts first?

  1. Maxillary central incisor
  2. Maxillary first molar
  3. Mandibular central incisor Correct answer.
  4. Mandibular first molar

Explanation

The mandibular primary central incisor is normally the first tooth to emerge, typically at about 6 to 10 months of age. Primary eruption generally follows a mandibular-before-maxillary and anterior-before-posterior sequence.

Question 9Anatomic Sciences

The temporalis muscle inserts on which mandibular structure?

  1. Pterygoid fovea
  2. Mandibular angle
  3. Coronoid process Correct answer.
  4. Condylar neck

Explanation

The temporalis converges into a tendon that inserts on the coronoid process and the anterior border of the ramus, elevating and retruding the mandible. The condylar neck and pterygoid fovea receive lateral pterygoid fibers and the angle receives the masseter and medial pterygoid.

Question 10Anatomic Sciences

The maxillary sinus drains into which nasal region?

  1. Nasopharynx
  2. Superior meatus
  3. Middle meatus Correct answer.
  4. Inferior meatus

Explanation

The maxillary sinus opens through the hiatus semilunaris into the middle meatus, and its ostium is placed high on the medial wall, which impairs gravity drainage. The nasolacrimal duct drains to the inferior meatus and the sphenoid sinus to the sphenoethmoidal recess.

Question 11Anatomic Sciences

Hertwig's epithelial root sheath is derived from which structure?

  1. Dental papilla
  2. Cervical loop Correct answer.
  3. Stellate reticulum
  4. Dental follicle

Explanation

After crown formation, the inner and outer enamel epithelia proliferate at the cervical loop to form the bilaminar Hertwig's root sheath, which induces root dentin formation and maps root number and shape. The dental papilla and follicle are of mesenchyme origin and form pulp, dentin, and periodontium.

Question 12Anatomic Sciences

Which principal fiber group of the periodontal ligament chiefly resists intrusive (axial) forces?

  1. Alveolar crest group
  2. Horizontal group
  3. Oblique group Correct answer.
  4. Apical group

Explanation

Oblique fibers run from bone apically to cementum coronally, so axial loading converts them to tension and transmits force as tension to the alveolar bone. The alveolar crest, horizontal, and apical groups are oriented to resist tipping and extrusive loads.

Question 13Anatomic Sciences

The maxillary artery is a terminal branch of which vessel?

  1. External carotid artery Correct answer.
  2. Facial artery
  3. Superficial temporal artery
  4. Internal carotid artery

Explanation

The external carotid artery terminates by dividing into the maxillary artery and the superficial temporal artery. The maxillary artery supplies the deep face, including the teeth, palate, and nasal cavity, via its maxillary, pterygoid, and sphenopalatine parts.

Question 14Anatomic Sciences

Lymph from the tip of the tongue drains first to which nodes?

  1. Parotid nodes
  2. Submandibular nodes
  3. Retropharyngeal nodes
  4. Submental nodes Correct answer.

Explanation

The lingual apex drains to the submental nodes, while the body drains to submandibular and deep cervical nodes and the posterior third drains bilaterally to deep cervical nodes. This pattern explains the midline crossover of apical tongue lymphatics.

Question 15Anatomic Sciences

In ideal (Class I) occlusion, the mesiobuccal cusp of the maxillary first molar occludes into which mandibular feature?

  1. Central fossa of the mandibular second molar
  2. Lingual groove of the mandibular first molar
  3. Buccal groove of the mandibular first molar Correct answer.
  4. Distal marginal ridge of the mandibular first molar

Explanation

The key to Class I occlusion is that the mesiobuccal cusp of the maxillary first molar lies in the buccal groove of the mandibular first molar. This same cusp-to-groove relationship places the maxillary canine between the mandibular canine and first premolar.

Question 16Anatomic Sciences

The mandibular foramen lies on which part of the mandible?

  1. Medial surface of the ramus Correct answer.
  2. Anterior border of the ramus
  3. Alveolar border of the body
  4. Lateral surface of the ramus

Explanation

The mandibular foramen is on the medial surface of the ramus, protected by the lingula, and transmits the inferior alveolar nerve and vessels. Its medial position explains why local anesthesia is delivered from the medial side of the ramus.

Question 17Anatomic Sciences

Hunter-Schreger bands in enamel reflect which feature?

  1. Enamel tufts at the DEJ
  2. Perikymata at the surface
  3. Change in rod direction Correct answer.
  4. Incremental growth lines

Explanation

Hunter-Schreger bands are alternating light and dark zones seen in longitudinal sections of enamel that arise from changes in the direction of enamel rods (prisms). They are a structural, not incremental, feature and are unrelated to the surface perikymata.

Question 18Anatomic Sciences

The highly mineralized dentin immediately lining each dentinal tubule is called:

  1. Peritubular dentin Correct answer.
  2. Intertubular dentin
  3. Predentin
  4. Tertiary dentin

Explanation

Peritubular (intratubular) dentin forms a more mineralized cuff around each odontoblast process and is lost in caries, causing tubule widening. Intertubular dentin fills the space between tubules, predentin is the unmineralized matrix at the pulp border, and tertiary dentin is formed in response to injury.

Question 19Anatomic Sciences

Weakness of the marginal mandibular branch of the facial nerve produces which sign?

  1. Numbness of the lower lip
  2. Inability to close the eye
  3. Loss of taste on the anterior tongue
  4. Lower lip deviation Correct answer.

Explanation

The marginal mandibular branch supplies the depressors of the lower lip and the orbicularis oris of the lower lip, so its loss causes the lower lip to deviate toward the unaffected side on smiling. Eyelid closure depends on the temporal and zygomatic branches, and sensation is trigeminal.

Question 20Anatomic Sciences

Which permanent tooth replaces the primary second molar?

  1. First premolar
  2. Canine
  3. Second molar
  4. Second premolar Correct answer.

Explanation

Each primary molar is succeeded by a premolar, so the primary second molar is replaced by the second premolar and the primary first molar by the first premolar. Permanent molars have no primary predecessors.

Question 21Anatomic Sciences

Failure of fusion of the two lateral palatal processes with each other and with the nasal septum produces which defect?

  1. Cleft of the upper lip
  2. Cleft of the primary palate
  3. Secondary cleft palate Correct answer.
  4. Mandibular cleft

Explanation

The secondary palate forms from the lateral palatal shelves, which elevate, fuse in the midline, and join the nasal septum; failure of these events yields a cleft of the secondary (hard and soft) palate. Clefts of the lip and primary palate arise from failure of fusion of the medial nasal and maxillary processes.

Question 22Anatomic Sciences

The superior head of the lateral pterygoid muscle inserts chiefly into which structure?

  1. Coronoid process
  2. Squamous part of the temporal bone
  3. Articular disc and capsule Correct answer.
  4. Pterygoid fovea of the condyle

Explanation

The superior head of the lateral pterygoid attaches to the articular disc and capsule and helps stabilize the disc during closure, while the inferior head inserts into the pterygoid fovea of the condyle and protrudes the mandible. The coronoid process receives the temporalis.

Question 23Anatomic Sciences

The facial vein communicates with the cavernous sinus by way of which vessel?

  1. Internal jugular vein
  2. Retromandibular vein
  3. Ophthalmic vein Correct answer.
  4. Pterygoid plexus

Explanation

The angular vein continues superiorly as the superior ophthalmic vein, which passes through the superior orbital fissure to reach the cavernous sinus; these channels are valveless, allowing retrograde spread of infection from the midface.

Question 24Anatomic Sciences

Which structure divides the parotid gland into superficial and deep lobes?

  1. Retromandibular vein
  2. Facial nerve Correct answer.
  3. Masseter muscle
  4. External carotid artery

Explanation

The facial nerve and its branches run through the gland and are used surgically to define superficial and deep lobes, which is why parotid surgery risks facial palsy. The external carotid and retromandibular vein lie within the gland but are not the standard dividing plane.

Question 25Anatomic Sciences

General sensation from the anterior part of the nasal septum is carried by which nerve?

  1. Posterior superior nasal nerve
  2. Greater palatine nerve
  3. Nasopalatine nerve
  4. Anterior ethmoidal nerve Correct answer.

Explanation

The anterior ethmoidal nerve, a branch of the nasociliary division of the ophthalmic nerve, supplies the anterior septum and anterior lateral nasal wall. The nasopalatine nerve supplies the posterior inferior septum, and the posterior superior nasal nerves supply the posterior nasal cavity.

Question 26Anatomic Sciences

Which ligament primarily limits posterior (retrusive) movement of the mandibular condyle?

  1. Temporomandibular ligament Correct answer.
  2. Pterygomandibular raphe
  3. Stylomandibular ligament
  4. Sphenomandibular ligament

Explanation

The temporomandibular ligament is the thickened lateral part of the joint capsule; its horizontal fibers tighten as the condyle moves backward, checking retrusion. Its oblique fibers also resist inferior displacement of the condyle.

Question 27Anatomic Sciences

Which nerve supplies motor fibers to the muscles of mastication?

  1. Trigeminal (mandibular division) Correct answer.
  2. Trigeminal (maxillary division)
  3. Facial nerve
  4. Glossopharyngeal nerve

Explanation

All four muscles of mastication develop from the first pharyngeal arch and are therefore innervated by the mandibular division of the trigeminal nerve. The maxillary division is purely sensory.

Question 28Anatomic Sciences

The inorganic portion of mature enamel consists mainly of which material?

  1. Hydroxyapatite Correct answer.
  2. Collagen type I
  3. Dicalcium phosphate
  4. Amorphous calcium carbonate

Explanation

Mature enamel is about 96% inorganic by weight, and that mineral is almost entirely crystalline hydroxyapatite. Enamel contains essentially no collagen.

Question 29Anatomic Sciences

How many roots does a typical permanent maxillary first molar have?

  1. Four
  2. Two
  3. One
  4. Three Correct answer.

Explanation

The permanent maxillary first molar normally has three roots: mesiobuccal, distobuccal, and palatal (lingual). This trifurcation gives it a broad, stable support.

Question 30Anatomic Sciences

Which muscle forms the principal floor of the mouth?

  1. Stylohyoid
  2. Anterior belly of digastric
  3. Mylohyoid Correct answer.
  4. Geniohyoid

Explanation

The paired mylohyoid muscles arise from the mylohyoid line and meet in a median raphe to form the muscular floor of the mouth. They support the tongue and floor-of-mouth contents and elevate the hyoid.

Question 31Anatomic Sciences

The facial nerve leaves the skull through which opening?

  1. Foramen ovale
  2. Stylomastoid foramen Correct answer.
  3. Jugular foramen
  4. Internal acoustic meatus

Explanation

The facial nerve enters the facial canal at the internal acoustic meatus and travels within the temporal bone, exiting the skull at the stylomastoid foramen before entering the parotid gland.

Question 32Anatomic Sciences

The sella turcica is a feature of which cranial bone?

  1. Frontal
  2. Sphenoid Correct answer.
  3. Ethmoid
  4. Temporal

Explanation

The sella turcica is a saddle-shaped depression on the superior surface of the body of the sphenoid bone; it houses the hypophysis (pituitary) in its hypophyseal fossa.

Question 33Anatomic Sciences

Which muscle elevates the soft palate during swallowing?

  1. Musculus uvulae
  2. Palatoglossus
  3. Levator veli palatini Correct answer.
  4. Tensor veli palatini

Explanation

The levator veli palatini arises from the temporal bone and passes into the soft palate, where contraction lifts the palate to close off the nasopharynx. The tensor veli palatini tenses the palate and opens the pharyngotympanic tube.

Question 34Anatomic Sciences

Which type of cementum contains cells within lacunae?

  1. Cellular cementum Correct answer.
  2. Acellular afibrillar cementum
  3. Acellular extrinsic fiber cementum
  4. Intermediate cementum

Explanation

Cellular cementum contains cementocytes resident in lacunae with canaliculi, and it is found chiefly on the apical third of the root and in furcations. Acellular cementum lacks entrapped cells.

Question 35Anatomic Sciences

Which gingival fiber group is the most numerous and attaches the gingiva to the tooth surface?

  1. Circular fibers
  2. Dentogingival fibers Correct answer.
  3. Transseptal fibers
  4. Alveologingival fibers

Explanation

Dentogingival fibers run from the cervical cementum into the lamina propria of the gingiva and are the most abundant of the gingival fiber groups. They help hold the marginal gingiva against the tooth.

Question 36Anatomic Sciences

The hypoglossal nerve leaves the cranial cavity through which opening?

  1. Hypoglossal canal Correct answer.
  2. Jugular foramen
  3. Carotid canal
  4. Foramen magnum

Explanation

Cranial nerve XII exits the posterior cranial fossa through the hypoglossal canal of the occipital bone. It then descends to supply the intrinsic and most extrinsic tongue muscles.

Question 37Anatomic Sciences

Which structure passes through the foramen ovale?

  1. Internal carotid artery
  2. Maxillary nerve
  3. Middle meningeal artery
  4. Mandibular nerve Correct answer.

Explanation

The foramen ovale in the greater wing of the sphenoid transmits the mandibular division of the trigeminal nerve along with the lesser petrosal nerve and accessory meningeal artery.

Question 38Anatomic Sciences

Meckel cartilage forms the skeletal core of which pharyngeal arch?

  1. Third
  2. Fourth
  3. Second
  4. First Correct answer.

Explanation

Meckel cartilage is the cartilage of the first (mandibular) arch and gives rise to the malleus, incus, sphenomandibular ligament, and much of the mandible through intramembranous ossification around it.

Question 39Anatomic Sciences

The stapes arises from the cartilage of which pharyngeal arch?

  1. Second Correct answer.
  2. Third
  3. First
  4. Fourth

Explanation

The stapes is derived from Reichert cartilage of the second (hyoid) arch, which also gives the styloid process and lesser horn of the hyoid. The second arch is innervated by the facial nerve.

Question 40Anatomic Sciences

The dental papilla gives rise to which dental tissues?

  1. Enamel and reduced enamel epithelium
  2. Cementum and periodontal ligament
  3. Alveolar bone and cementum
  4. Dentin and pulp Correct answer.

Explanation

Cells of the dental papilla differentiate into odontoblasts, which secrete dentin, and the remaining papilla becomes the dental pulp. Enamel is produced separately by the enamel organ.

Question 41Anatomic Sciences

Which muscle protrudes the tongue?

  1. Genioglossus Correct answer.
  2. Styloglossus
  3. Palatoglossus
  4. Hyoglossus

Explanation

The genioglossus runs from the genial tubercle of the mandible to the tongue and, acting bilaterally, pulls the tongue forward; unilateral contraction deviates the tongue toward the opposite side.

Question 42Anatomic Sciences

The inferior alveolar artery is a branch of which artery?

  1. Superficial temporal artery
  2. Lingual artery
  3. Maxillary artery Correct answer.
  4. Facial artery

Explanation

The inferior alveolar artery arises from the first (mandibular) part of the maxillary artery and enters the mandibular foramen to supply the mandibular teeth and bone.

Question 43Anatomic Sciences

Preganglionic parasympathetic fibers destined for the parotid gland synapse in which ganglion?

  1. Pterygopalatine ganglion
  2. Ciliary ganglion
  3. Submandibular ganglion
  4. Otic ganglion Correct answer.

Explanation

Glossopharyngeal parasympathetic fibers travel by way of the lesser petrosal nerve to synapse in the otic ganglion; postganglionic fibers then reach the parotid gland along the auriculotemporal nerve.

Question 44Anatomic Sciences

Which immunoglobulin is the predominant antibody in whole saliva?

  1. IgA Correct answer.
  2. IgM
  3. IgE
  4. IgG

Explanation

Secretory IgA, produced by plasma cells near the salivary ducts and transported with a secretory component, is the major immunoglobulin of saliva. It helps limit microbial colonization of oral surfaces.

Question 45Anatomic Sciences

Which nerve passes through the incisive canal to supply the anterior hard palate?

  1. Infraorbital nerve
  2. Nasopalatine nerve Correct answer.
  3. Greater palatine nerve
  4. Lesser palatine nerve

Explanation

The nasopalatine nerve descends through the incisive canal from the nasal cavity to supply sensation to the palatal mucosa behind the central incisors. It is a branch of the maxillary division of the trigeminal nerve.

Question 46Anatomic Sciences

Which nerve provides general sensation to the buccal gingiva of the mandibular permanent molars?

  1. Buccal nerve Correct answer.
  2. Lingual nerve
  3. Inferior alveolar nerve
  4. Mylohyoid nerve

Explanation

The buccal nerve, a branch of the mandibular division of the trigeminal nerve, supplies the mucosa and gingiva of the cheek and the buccal gingiva of the mandibular molars. The gingiva lingual to these teeth is supplied by the lingual nerve.

Question 47Anatomic Sciences

The pterygoid venous plexus drains chiefly into which vein?

  1. Facial vein
  2. Maxillary vein Correct answer.
  3. Internal jugular vein
  4. Retromandibular vein

Explanation

Blood from the pterygoid plexus collects into the maxillary vein, which then joins the superficial temporal vein to form the retromandibular vein. The plexus also communicates with the cavernous sinus through emissary veins.

Question 48Anatomic Sciences

The submandibular space is bounded superiorly by which structure?

  1. The mylohyoid muscle Correct answer.
  2. The geniohyoid muscle
  3. The hyoid bone
  4. The deep cervical fascia

Explanation

The submandibular space lies below the mylohyoid muscle and above the hyoid bone, with the mylohyoid forming its roof. Because of this relationship, infections of mandibular molar origin can spread into the space from below the mylohyoid line.

Question 49Anatomic Sciences

Odontoblasts are derived from which embryonic source?

  1. Neural crest ectomesenchyme Correct answer.
  2. First arch mesoderm
  3. Surface ectoderm
  4. Pharyngeal pouch endoderm

Explanation

Odontoblasts differentiate from ectomesenchymal cells of neural crest origin that populate the dental papilla. Surface ectoderm of the stomodeum gives rise only to the enamel organ and enamel.

Question 50Anatomic Sciences

Chorda tympani fibers bound for the submandibular ganglion travel with which nerve?

  1. Mylohyoid nerve
  2. Inferior alveolar nerve
  3. Lingual nerve Correct answer.
  4. Buccal nerve

Explanation

Chorda tympani joins the lingual nerve in the infratemporal fossa and is distributed with it to the submandibular ganglion, where the parasympathetic fibers synapse. Postganglionic fibers then reach the submandibular and sublingual glands.