Free NBDE MCQ Questions and Answers — Questions and Answers

Question 1: Which field of the dentistry is defined as the science and art of preventing and controlling detank diseases and promoting dental health through organized community efforts?

Pediatric Dentistry
Prosthodontics
Endodontics
Dental Public Health (Correct answer)
Periodontics

Correct answer: Dental Public Health

Dental Public Health is a specialized field of dentistry focused on the science and art of preventing and controlling dental diseases and promoting oral health within communities. It involves organized efforts to assess population needs, develop policies, and implement programs to improve oral health outcomes for groups rather than individual patients.

Question 2: An 11-year-old girl presents with a maxillary midline diastema of less than 2mm. The patient's mother is concerned about her appearance and asks you to close the space. What is the appropriate management in this situation?

Close the space with an orthodontic appliance
Reassure the mother and wait for the maxillary canines to erupt (Correct answer)
Close the space with 5 surface composite fillings
Investigate further to determine cause of the diastema

Correct answer: Reassure the mother and wait for the maxillary canines to erupt

A maxillary midline diastema of less than 2mm in an 11-year-old is often a transient condition known as the 'ugly duckling stage.' As the maxillary canines erupt, they typically exert pressure on the roots of the lateral and central incisors, causing the diastema to spontaneously close. Therefore, observation and reassurance are usually the appropriate initial management.

Question 3: An 85-year-old petite female presents for her recall appointment. She notes that her husband of 55 years died 6 months ago. Since then, she notes she has lost 15 pounds and is having difficulty with decreased appetite. What is the most appropriate step should you take yo aid this patient?

Recommend adding liquid nutritional beverages to her diet
Refer her to her family physician for a more in-depth check-up (Correct answer)
Refer her to a registered dietician
Congratulate her on her weight loss
Give her a copy of the national food guide to healthy eating

Correct answer: Refer her to her family physician for a more in-depth check-up

Significant, unintentional weight loss and decreased appetite, especially following a major life stressor like the death of a spouse, can indicate underlying medical or psychological issues such as depression, malnutrition, or other systemic diseases. A dental professional should refer the patient to their family physician for a comprehensive medical evaluation to rule out serious health concerns.

Question 4: To diagnose periodontal disease, the most important factor is:

The presence of bleeding on probing
The vitality of the teeth
Attachment loss (Correct answer)
The presence of pain on probing
The mobility of the teeth

Correct answer: Attachment loss

While bleeding on probing, pain, and mobility are important clinical signs, the most definitive diagnostic factor for periodontal disease is clinical attachment loss. Attachment loss refers to the irreversible destruction of the periodontal ligament and alveolar bone, leading to deeper periodontal pockets and gingival recession. It signifies the progression of the disease beyond simple gingivitis.

Question 5: Which stage of necrotizing ulcerative gingivitis occurs first?

The ulceration extends from the tip of the interdental papilla to the marginal gingival
The bone is exposed
The attached gingiva is affected
The tip of the interdental papilla is affected (Correct answer)
Necrosis appears on the cheek

Correct answer: The tip of the interdental papilla is affected

Necrotizing ulcerative gingivitis (NUG) typically begins with the necrosis and ulceration of the tips of the interdental papillae. This initial presentation gives NUG its characteristic 'punched-out' appearance. The ulceration then progresses to the marginal gingiva and can, in severe cases, extend to the attached gingiva.

Question 6: Which disease is characterized by necrosis of the marginal gingival tissue and interdental papillae?

Chronic periodontal disease
Aggressive periodontal disease
Necrotizing periodontal disease (Correct answer)
Abscesses of the periodontium
None of the above

Correct answer: Necrotizing periodontal disease

Necrotizing periodontal disease (NPD), including Necrotizing Ulcerative Gingivitis (NUG), is specifically characterized by the rapid onset of necrosis and ulceration of the gingival margins and interdental papillae. This leads to the classic "punched-out" appearance of the papillae, often accompanied by pain, bleeding, and a distinctive fetid odor. Other forms of periodontal disease do not primarily present with tissue necrosis as a defining feature.

Question 7: An acute apical periodontitis would present as:

A tooth that feels “long” and extremely painful on biting (Correct answer)
An incidental finding on an asymptomatic tooth
A tooth that is mildly painful on biting
A painful gingival swelling absent of tooth findings

Correct answer: A tooth that feels “long” and extremely painful on biting

Acute apical periodontitis is an inflammatory condition of the periapical tissues, typically caused by pulpal necrosis or trauma. The inflammation and edema in the periodontal ligament space cause the tooth to extrude slightly, making it feel "long" and exquisitely painful upon biting or percussion. This distinct sensation is a hallmark symptom differentiating it from other dental pain.

Question 8: Which of the following antihypertensives is known to cause gingival hyperplasia in patients?

Calcium channel blockers (Correct answer)
Alpha-adrenergic receptor blockers
ACE inhibitors
ATII receptor antagonists
Beta-adrenergic receptor blockers

Correct answer: Calcium channel blockers

Calcium channel blockers, such as nifedipine, amlodipine, and verapamil, are well-known to cause drug-induced gingival hyperplasia as a side effect. This condition involves an abnormal overgrowth of the gingival tissues. While other antihypertensives have various side effects, gingival hyperplasia is a characteristic adverse effect primarily associated with this class of drugs.

Question 9: Which of the following drugs is most likely to result in decreased metabolism of opioids that undergo hepatic metabolism?

Carbamazepine
Phenytoin
St. John’s wort
Rifampicin
Diltiazem (Correct answer)

Correct answer: Diltiazem

Diltiazem is a calcium channel blocker that acts as a potent inhibitor of the cytochrome P450 (CYP450) enzyme system, particularly CYP3A4, in the liver. Many opioids, such as fentanyl, oxycodone, and hydrocodone, are metabolized by these enzymes. By inhibiting CYP450, diltiazem decreases the metabolism of these opioids, leading to increased plasma concentrations and a higher risk of adverse effects.

Question 10: A 22-year-old patient with an unrepaired cyanotic congenical heart defect is scheduled for a routine teeth cleaning. The patient is allergc to penicillins. Which of the following should be done with regards to this patient prior to their dental procedure?

Administer oral prophylactic amoxicillin
Administer intravenous prophylactic cefazolin
Administer intravenous prophylactic ampicillin
Administer oral prophylactic clindamycin (Correct answer)
Administer intravenous prophylactic clindamycin
Prophylaxis is not necessary in this patient

Correct answer: Administer oral prophylactic clindamycin

For patients with high-risk cardiac conditions, such as unrepaired cyanotic congenital heart defects, antibiotic prophylaxis is required before dental procedures that involve manipulation of gingival tissue. Since the patient is allergic to penicillins, clindamycin is the recommended alternative for oral administration according to American Heart Association guidelines. Intravenous administration is typically reserved for patients unable to take oral medication.

Question 11: Studies show that a minimal amount of ferrule is necessary for an endodontically treated tooth that is also treated with a dowel in order to prevent fracture by te dowel. What is the minimum ferrule needed?

0.5mm
1mm
3mm
1.5-2mm (Correct answer)
4mm

Correct answer: 1.5-2mm

A ferrule is a band of tooth structure encircling the tooth, typically 360 degrees, above the crown margin. For endodontically treated teeth restored with a dowel and core, a minimum ferrule of 1.5-2mm in height is crucial. This provides a "hoop effect" that enhances the resistance of the tooth to fracture, especially under occlusal forces, by distributing stress and protecting the root from wedging forces exerted by the dowel.

Question 12: For a short clinical crown, what would be the greatest advantages to adding buccal grooves to the preparation?

Increase structural durability
Increase retention
Increase resistance (Correct answer)
Improves casting
Improves path of draw

Correct answer: Increase resistance

For a short clinical crown, retention and resistance are critical for the longevity of the restoration. Buccal (and lingual) grooves are added to a crown preparation to increase the total surface area and improve the resistance form. This helps prevent the crown from dislodging due to tipping or rotational forces, which is particularly important when the axial walls are short and offer less inherent resistance.

Question 13: When casting gold in prosthodontics, the portion of the flame used to heat the metal is:

The anodizing zone
The redox zone
The reducing zone (Correct answer)
The oxidizing zone

Correct answer: The reducing zone

When casting gold in prosthodontics, the metal should be heated in the reducing zone of the flame. This zone, characterized by its blue color and located just beyond the tip of the inner cone, has an excess of uncombusted gases. This creates a reducing atmosphere that prevents oxidation of the molten gold, ensuring a clean and strong casting without incorporating oxides that could weaken the final restoration.

Question 14: Which type of margin is usually situated on hard enamel and is a preferred choice whenever possible when prepping a crown?

Supragingival (Correct answer)
Equigingival
Subgingival
All of the above
None of the above

Correct answer: Supragingival

Supragingival margins are generally the preferred choice for crown preparations whenever possible because they are easier to prepare accurately and inspect. They are also more accessible for impression taking and allow for better plaque control by the patient, promoting gingival health. Placing margins on hard enamel, rather than dentin or cementum, also provides a stronger, more predictable bond for the restorative material.

Question 15: Composite resin restorations may use cavity liners for the purpose of:

Better protecting the resin from fluid inside the tooth
Reducing pulpal irritation in deep cavities (Correct answer)
Improving adhesion of the resin to the pulpal floor
Altering the translucency of the composite material

Correct answer: Reducing pulpal irritation in deep cavities

Cavity liners, such as calcium hydroxide or glass ionomer, are used in deep composite resin restorations primarily to reduce pulpal irritation. They act as a protective barrier against chemical irritants from the restorative material and thermal changes, promoting pulpal health. While they may offer some sealing, their main role is therapeutic and protective for the pulp in close proximity to the preparation.

Question 16: A smear biopsy reveals a large, tangled mass of gram-positive hyphae. What would be your diagnosis?

Streptococcus pyogenes
Staphylococcus aureus
Candida albicans (Correct answer)
Streptococcus mutans

Correct answer: Candida albicans

Candida albicans is a dimorphic fungus that commonly presents as a large, tangled mass of gram-positive hyphae and pseudohyphae, along with yeast cells, on a smear biopsy. This characteristic microscopic appearance is diagnostic for candidiasis, distinguishing it from bacterial infections caused by Streptococcus or Staphylococcus species, which would appear as cocci or chains/clusters of cocci.

Free NBDE MCQ Questions and Answers

Which field of the dentistry is defined as the science and art of preventing and controlling detank diseases and promoting dental health through organized community efforts?