NBDHE Dental Materials and Procedures Flashcards

A dental hygienist prepares an alginate impression for a study model. Upon inspection, the final impression has a grainy, rough surface and lacks fine detail. Which of the following is the MOST likely cause of this error?

Answer: Inadequate spatulation of the powder and liquid

Inadequate spatulation, or undermixing, fails to properly dissolve the alginate powder into the water. This results in unreacted particles remaining in the mix, leading to a grainy texture and a weaker impression that cannot accurately capture surface details.

Which of the following is a primary advantage of using a microfilled composite resin for a Class V restoration on a maxillary canine?

Answer: High polishability resulting in excellent esthetics

Microfilled composites contain very small filler particles (e.g., 0.04 micrometers), which allows the material to be polished to a very smooth, high-gloss, and enamel-like surface. This makes them an ideal choice for esthetically critical areas like the facial surface of an anterior tooth. Their lower filler content, however, makes them weaker and less fracture-resistant than hybrid composites.

A patient requires a temporary crown on a tooth that is sensitive and diagnosed with reversible pulpitis. The dentist needs a luting cement that will have a palliative, or soothing, effect on the pulp. Which cement is the BEST choice?

Answer: Zinc Oxide Eugenol (ZOE) cement

Zinc Oxide Eugenol (ZOE) cement contains eugenol (oil of cloves), which is known for its sedative or palliative effect on the dental pulp. This property makes it an excellent choice for temporary cementation on teeth that are sensitive or have reversible pulpitis. The other cements listed do not possess this soothing quality.

The long-term retention of a pit and fissure sealant is MOST dependent on which of the following steps during its application?

Answer: Meticulous isolation to maintain a dry field

The success of a sealant relies on the micromechanical bond created between the resin and the etched enamel. Any contamination of the etched surface by saliva or moisture will interfere with the formation of resin tags and prevent a proper bond, leading to premature sealant failure. Therefore, maintaining a completely dry field is the single most critical factor for long-term retention.

A dental hygienist is performing coronal polishing on a patient with generalized enamel and a few composite restorations. To minimize abrasion and preserve the integrity of these surfaces, the polishing agent selected should have which characteristics?

Answer: Low hardness and small, round particle size

The rate of abrasion is determined by the characteristics of the abrasive particles and the application technique. To be least abrasive, a polishing agent should have low hardness (softer than the surface being polished), small particle size, and regular, rounded particle shapes. This combination, applied with light pressure, will clean and polish with minimal removal of surface material.

A patient is undergoing an in-office vital tooth whitening procedure. The material applied to the teeth is a high-concentration gel that works by oxidizing stain molecules. What is the primary active ingredient in MOST in-office tooth whitening systems?

Answer: Hydrogen peroxide

Most professionally applied, in-office whitening systems use a high concentration of hydrogen peroxide (typically 15-38%). Hydrogen peroxide is a powerful oxidizing agent that breaks down into water and oxygen radicals, which penetrate the tooth structure and break down pigmented chromogens into smaller, colorless molecules. Carbamide peroxide, which breaks down into hydrogen peroxide and urea, is more commonly used in lower concentrations for at-home whitening trays.