Free NBDE Questions and Answers — Questions and Answers
Question 1: During the swallowing process, which nerve is responsible for elevating the soft palate?
- Facial nerve
- Vagus nerve (Correct answer)
- Vestibulocochlear nerve
- Hypoglossal nerve
Correct answer: Vagus nerve
The Vagus nerve (Cranial Nerve X) innervates most of the muscles of the soft palate, pharynx, and larynx. Specifically, it supplies the levator veli palatini muscle, which is responsible for elevating the soft palate during swallowing (deglutition) to prevent food from entering the nasopharynx.
Question 2: The oral cavity is separated from which body cavity by the palatine bone of the mouth?
- Submandibular space
- Nasal cavity (Correct answer)
- Buccal space
- Mental space
Correct answer: Nasal cavity
The hard palate, which forms the roof of the mouth, is primarily composed of the palatine processes of the maxillae and the horizontal plates of the palatine bones. This bony structure serves as a partition, effectively separating the oral cavity below from the nasal cavity above.
Question 3: Which vessels are responsible for supplying the buccal gingiva that covers tooth #3?
- Inferior alveolar vessels
- Greater palatine vessels
- Middle superior alveolar vessels
- Posterior superior alveolar vessels (Correct answer)
Correct answer: Posterior superior alveolar vessels
Tooth #3 is the maxillary right first molar. The posterior superior alveolar artery, a branch of the maxillary artery, supplies the maxillary molars and premolars, as well as the buccal gingiva in that region. Therefore, it is the correct vessel for supplying the buccal gingiva covering tooth #3.
Question 4: The surgeon notices considerable quantities of blood from the artery that runs medial to the neck of the mandibular condyle while healing an injury to the temporomandibular joint. What artery has been damaged?
- Maxillary artery (Correct answer)
- Internal carotid artery
- Facial artery
- External carotid artery
Correct answer: Maxillary artery
The maxillary artery is a major branch of the external carotid artery and is located medial to the neck of the mandibular condyle. It supplies numerous structures in the deep face, including the temporomandibular joint region. Damage to this artery during trauma or surgery in this area would result in significant bleeding.
Question 5: When glycogen is degraded, which of the following compounds is primarily produced?
- Glycogen phosphorylase
- Protein kinase
- Glucose 1-Phosphate (Correct answer)
- Glucagon Synthase
Correct answer: Glucose 1-Phosphate
Glycogen degradation, or glycogenolysis, is primarily catalyzed by glycogen phosphorylase. This enzyme breaks the alpha-1,4 glycosidic bonds in glycogen, releasing glucose units as glucose 1-phosphate. Glucose 1-phosphate is then converted to glucose 6-phosphate for further metabolic use.
Question 6: The periodontal ligament (PDL) receives its blood supply from the:
- Lingual artery
- Ascending pharyngeal artery
- Maxillary artery (Correct answer)
- Occipital artery
Correct answer: Maxillary artery
The periodontal ligament (PDL) has a rich vascular supply, primarily derived from branches of the maxillary artery. These branches include the superior and inferior alveolar arteries, which give off smaller vessels that penetrate the alveolar bone and supply the PDL fibers, cementum, and alveolar bone proper.
Question 7: Where does glycogen synthesis generally occur?
- Cytosol (Correct answer)
- Liver
- Endoplasmic reticulum
Correct answer: Cytosol
Glycogen synthesis, known as glycogenesis, is a metabolic pathway that occurs primarily in the cytoplasm (cytosol) of cells. While the liver and muscles are the main organs for glycogen storage, the enzymatic reactions for building glycogen from glucose take place within the cytosol.
Question 8: The conversion of glucose-6-P to glycogen is called:
- Glycogenesis (Correct answer)
- Glycolysis
- Gluconeogenesis
- Glycogenolysis
Correct answer: Glycogenesis
Glycogenesis is the metabolic process by which glycogen is synthesized from glucose. Glucose-6-phosphate is an intermediate in this pathway, being converted to glucose-1-phosphate and then to UDP-glucose before being added to the growing glycogen chain by glycogen synthase.
Question 9: Hemoglobin molecules are required for oxygen transportation. <br> Only one oxygen molecule can bind to a molecule of hemoglobin.
- The first statement is true, the second is false (Correct answer)
- The first statement is false, the second is true
- Both statements are true
- Both statements are false
Correct answer: The first statement is true, the second is false
The first statement is true: Hemoglobin is indeed the primary protein responsible for oxygen transportation in the blood. However, the second statement is false: Each hemoglobin molecule is composed of four heme groups, and each heme group can bind one oxygen molecule, meaning a single hemoglobin molecule can bind up to four oxygen molecules.
Question 10: Which type of tooth is most commonly affected by supernumerary teeth?
- Molars
- Incisors (Correct answer)
- Canines
- Premolars
Correct answer: Incisors
Supernumerary teeth, or hyperdontia, are extra teeth that appear in addition to the regular number of teeth. The most common type of supernumerary tooth is a mesiodens, which is typically found in the maxillary anterior region, specifically between the central incisors.
Question 11: What is the most common cause of localized aggressive periodontitis?
- Bacterial infection (Correct answer)
- Genetics
Correct answer: Bacterial infection
Localized aggressive periodontitis (LAP) is a severe form of periodontal disease characterized by rapid destruction of periodontal tissues. While genetic factors can play a role, the primary and most common cause, like all forms of periodontitis, is a bacterial infection, specifically certain virulent strains such as *Aggregatibacter actinomycetemcomitans*.
Question 12: Which dental material is commonly used for its biocompatibility and ability to bond to tooth structure?
- Good
- Amalgam
- Composite resin (Correct answer)
- Zinc oxide eugenol
Correct answer: Composite resin
Composite resin is a widely used dental restorative material known for its excellent biocompatibility and aesthetic qualities. Its key advantage is its ability to bond adhesively to tooth structure (enamel and dentin) through a bonding agent, allowing for conservative preparations and strengthening the remaining tooth structure.
Question 13: What is the primary function of the temporomandibular joint (TMJ)?
- Breathing
The temporomandibular joint (TMJ) is a complex synovial joint that connects the mandible (lower jaw) to the temporal bone of the skull. Its primary function is to facilitate all movements of the jaw, including opening and closing the mouth, protrusion, retrusion, and lateral excursions, which are essential for chewing, speaking, and swallowing.
Question 14: Which type of dental radiograph is best for detecting interproximal caries?
- Periapical
- Occlusal
- Bitewing (Correct answer)
- Panoramic
Correct answer: Bitewing
Bitewing radiographs are specifically designed to show the crowns of both maxillary and mandibular teeth in a single image, with an emphasis on the interproximal (between teeth) surfaces. This angulation and focus make them the most effective type of radiograph for detecting early carious lesions in these areas, which are often difficult to visualize clinically.
Question 15: What is the main purpose of a dental sealant?
- Teeth whitening
- Preventing gum desease
- Preventing cavities (Correct answer)
- Treating tooth sensitivity
Correct answer: Preventing cavities
Dental sealants are thin, plastic coatings applied to the chewing surfaces of back teeth (molars and premolars), where pits and fissures are common. These sealants act as a protective barrier, preventing food particles and bacteria from getting into the grooves and causing cavities (dental caries).
Question 16: Which dental condition is characterized by the grinding or clenching of teeth, often during sleep?
- Bruxism (Correct answer)
- Gingivitis
- Malocclusion
- Dental caries
Correct answer: Bruxism
Bruxism is the medical term for the involuntary grinding or clenching of teeth, often occurring during sleep or periods of stress. This condition can lead to tooth wear, jaw pain, and headaches. The other options describe different dental issues: gingivitis is gum inflammation, malocclusion is an improper bite, and dental caries are cavities.
During the swallowing process, which nerve is responsible for elevating the soft palate?