Free NBDE Part II Questions and Answers

Question 1

Enamel's structural degeneration is brought on by:

Accepted Answer

Lowered pH

Answer

Enamel's structural degeneration, or demineralization, is primarily caused by a lowered pH in the oral environment. When cariogenic bacteria metabolize sugars, they produce acids that decrease the pH below the critical level (approximately 5.5 for enamel). This acidic environment causes calcium and phosphate ions to leach out of the enamel, leading to its breakdown and the formation of carious lesions.

Question 2

For remineralization of onset lesions to take place, what must be ample?

Accepted Answer

Fluoride

Answer

For remineralization of early carious lesions to occur effectively, an ample supply of fluoride is crucial. Fluoride ions incorporate into the demineralized enamel, forming fluorapatite, which is more resistant to acid dissolution than the original hydroxyapatite. It also attracts calcium and phosphate ions from saliva, facilitating the repair process and strengthening the tooth structure.

Question 3

What allows caries to infiltrate the dento-enamel junction?

Accepted Answer

Frank caries

Answer

Frank caries refers to a carious lesion that has progressed beyond the initial stages and has clearly penetrated the enamel, reaching and often spreading along the dento-enamel junction (DEJ). At the DEJ, the caries can spread laterally due to the change in tooth structure, making it a critical point for the progression of the disease into the dentin.

Question 4

What is the most prevalent cariogenic bacterium at the root surface of caries?

Accepted Answer

Actinomyces viscus

Answer

Actinomyces viscus (now often referred to as Actinomyces naeslundii genospecies 2) is widely recognized as a primary etiological agent in root surface caries. Unlike coronal caries, which is often initiated by S. mutans, root surface caries occurs on exposed root surfaces and is strongly associated with the acidogenic and aciduric properties of Actinomyces species, particularly A. viscus.

Question 5

Which three regions of carious dentin can remineralize?

Accepted Answer

Normal dentin, sub-transparent dentin, and transparent dentin

Answer

Carious dentin can be broadly categorized into an outer infected layer and an inner affected layer. The inner affected dentin, which includes normal dentin, sub-transparent dentin, and transparent dentin, is demineralized but not yet irreversibly infected with bacteria. These layers retain their collagen matrix and are capable of remineralization if the bacterial insult is removed and appropriate conditions are present.

NBDE - National Board Dental Examination Practice Test

NBDE - National Board Dental Examination Practice Test

Free NBDE Part II Questions and Answers