Free NBDE Knowledge Questions and Answers — Questions and Answers

Question 1: What is the most common form of gingival disease?

Plaque-induced gingivitis (Correct answer)
Non-plaque-induced gingivitis
Generalized chronic periodontitis
Generalized aggressive periodontitis
Necrotizing ulcerative gingivitis

Correct answer: Plaque-induced gingivitis

Plaque-induced gingivitis is the most prevalent form of gingival disease, characterized by inflammation of the gums primarily caused by the accumulation of bacterial plaque along the gumline. It is reversible with effective oral hygiene practices and professional dental cleaning, distinguishing it from more advanced periodontal conditions.

Question 2: Which of the following systematic diseases is not associated with aphthous-like ulcerations?

Irritable bowel syndrome (Correct answer)
Behcet syndrome
Celiac disease
IgA deficiency
Nutritional deficiencies

Correct answer: Irritable bowel syndrome

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder primarily affecting the large intestine, characterized by symptoms like abdominal pain and altered bowel habits. Unlike conditions such as Behcet syndrome, celiac disease, or certain nutritional deficiencies, IBS is not typically associated with the development of aphthous-like ulcerations in the oral cavity.

Question 3: What salivary gland disorder would you suspect with your patient who suffers from keratoconjunctivits sicca and xerostomia?

Rheumatoid arthritis
Trigeminal neuralgia
Sialadenosis
Pleomorphic adenoma
Sjogren syndrome (Correct answer)

Correct answer: Sjogren syndrome

Sjogren syndrome is a chronic autoimmune disease characterized by the immune system attacking moisture-producing glands, predominantly the salivary and lacrimal glands. This leads to the hallmark symptoms of xerostomia (dry mouth) and keratoconjunctivitis sicca (dry eyes), which are indicative of the condition.

Question 4: What is a common ingredient in soft drinks, gum candy, toothpaste, breath fresheners, dental floss that often causes contact stomatitis?

Preservatives
Xylitol
Riboflavin
Flavoring (Correct answer)
Sorbitol

Correct answer: Flavoring

Flavoring agents, particularly cinnamon and spearmint, are common ingredients in oral products like toothpaste, gum, and candies that frequently cause contact stomatitis. This allergic reaction manifests as redness, burning, and ulcerations in the oral mucosa due to direct contact with the allergen.

Question 5: Which virus is associated with Forchheimer's sign?

Mumps
Rubeola
Rubella (Correct answer)
HIV
Hand-foot-and-mouth disease

Correct answer: Rubella

Forchheimer's sign, characterized by small, red macules or petechiae on the soft palate, is a classic early enanthem associated with Rubella (German measles) infection. This distinct oral manifestation helps in the clinical diagnosis of Rubella, differentiating it from other viral exanthems.

Question 6: A patients X-rays revealed lesions located on the substantia nigra portion of his brain. Which of the following disease may this patient be diagnosed with?

Parkinson’s disease (Correct answer)
Huntington’s disease
Crohn’s disease
Multiple Sclerosis
Hyperthyroidism

Correct answer: Parkinson’s disease

Parkinson's disease is a progressive neurodegenerative disorder caused by the degeneration of dopamine-producing neurons in the substantia nigra region of the brain. Lesions or damage in this specific area are directly responsible for the characteristic motor symptoms observed in patients with Parkinson's disease.

Question 7: What is the resting membrane potential of a cell that is in state of domancy?

-60 mV
-70 mV (Correct answer)
-80 mV
+60 mV
+70 mV

Correct answer: -70 mV

The resting membrane potential of a typical neuron or muscle cell in a dormant state is approximately -70 mV. This negative charge inside the cell relative to the outside is maintained by the differential distribution of ions, primarily potassium and sodium, across the cell membrane through ion channels and pumps.

Question 8: The zona glomerulosa is responsible for:

Synthesis of androgens
Synthesis of aldosterone (Correct answer)
Synthesis of cortisol
Synthesis of ACTH

Correct answer: Synthesis of aldosterone

The zona glomerulosa is the outermost layer of the adrenal cortex and is specifically responsible for the synthesis and secretion of mineralocorticoids. Its primary product is aldosterone, a hormone crucial for regulating blood pressure and electrolyte balance by controlling sodium and potassium levels in the body.

Question 9: A heterotrimeric protein composed of three individual peptide chains describes:

Hemoglobin
Myoglobin
Collagen (Correct answer)
Elastin

Correct answer: Collagen

Collagen is the most abundant protein in mammals and is characterized by its triple-helical structure, formed by three polypeptide alpha chains. These chains can be identical or different, making it a heterotrimeric (or homotrimeric) protein. This unique structure provides collagen with its high tensile strength, essential for its role in connective tissues like bone, skin, and teeth.

Question 10: Which of the following is the most common type of occlusion in a normal dentition?

Class I (Correct answer)
Class II Division 1
Class II Division 2
Class III

Correct answer: Class I

Class I occlusion, also known as neutroclusion, is characterized by a normal anteroposterior relationship of the jaws, where the mesiobuccal cusp of the maxillary first molar occludes with the mesiobuccal groove of the mandibular first molar. This classification represents the ideal or most common occlusal relationship in a healthy dentition, indicating a balanced and functional bite.

Question 11: What happens when dental plaque adheres securely to the tooth's surface?

Carious lesions (Correct answer)
Cavities
Saliva increases
Fluoridation

Correct answer: Carious lesions

When dental plaque, a biofilm of bacteria, adheres securely to the tooth surface, the bacteria metabolize dietary sugars to produce acids. These acids demineralize the enamel and dentin, leading to the formation of carious lesions, commonly known as tooth decay. If left untreated, these lesions can progress into cavities.

Question 12: What promotes remineralization and has antibacterial qualities?

Tooth decay
Acid reflux
Saliva (Correct answer)
Carioprotective

Correct answer: Saliva

Saliva plays a crucial role in maintaining oral health by promoting remineralization and possessing antibacterial qualities. It contains minerals like calcium and phosphate that can repair early enamel lesions, and its buffering capacity helps neutralize acids produced by plaque bacteria. Additionally, saliva contains various antimicrobial components that help control bacterial growth.

Question 13: Fluoridation can help to reduce the prevalence of caries. What age group is this especially true for?

The elderly
Infants
Children (Correct answer)
Middle-aged adults

Correct answer: Children

Fluoridation is highly effective in reducing caries prevalence, especially in children, because their teeth are still developing and erupting. During these formative years, fluoride incorporates into the enamel structure, making it more resistant to acid attacks. It also promotes remineralization of early lesions and inhibits bacterial acid production, offering significant protection.

Question 14: What theory includes the increased fluid in tooth tubules, which deforms pulp nerve terminals and causes pain response?

Ad-hoc Theory
Cold Tooth Theory
Hydrodynamic Theory (Correct answer)
Dental Plaque Organism Theory

Correct answer: Hydrodynamic Theory

The Hydrodynamic Theory, proposed by Brännström, explains dentin hypersensitivity and pain response. It posits that stimuli like cold or air cause rapid fluid movement within the dentinal tubules. This fluid movement then deforms the odontoblastic processes and associated nerve endings in the pulp, triggering a pain signal.

Question 15: What caries is caused by common cariogenic bacteria like Streptococcus mutans and Lactobacilli?

Smooth surface
Dental plaque
Root surface
Coronal caries (Correct answer)

Correct answer: Coronal caries

Coronal caries refers to tooth decay affecting the crown of the tooth, which includes the enamel and dentin. This type of caries is primarily initiated by common cariogenic bacteria such as Streptococcus mutans and Lactobacilli, which ferment dietary carbohydrates to produce acids that demineralize the tooth structure. It is the most common form of dental caries.

Question 16: What dental plaque organism is discovered first while making an early diagnosis?

Actinomyces naeslundi
Lactobacilli
Streptococcus sanguis (Correct answer)
Peptococcus

Correct answer: Streptococcus sanguis

Streptococcus sanguis (now often referred to as Streptococcus mitis biovar 2) is one of the primary colonizers of the tooth surface, playing a significant role in the initial formation of dental plaque. It is among the first bacteria to adhere to the pellicle-coated enamel, establishing a foundation for subsequent bacterial colonization and biofilm development. Therefore, its presence is indicative of early plaque formation.

Free NBDE Knowledge Questions and Answers

What is the most common form of gingival disease?