ADEX Dental Hygiene Dental Biomaterials Questions and Answers — Questions and Answers
Question 1: A patient has a full gold crown on tooth #30 and a porcelain-fused-to-metal (PFM) crown on tooth #19. Which polishing agent is most appropriate for the porcelain surface to achieve a high luster without causing abrasion?
- Coarse pumice
- Tin oxide
- Diamond polishing paste (Correct answer)
- Sodium bicarbonate
Correct answer: Diamond polishing paste
Porcelain is a very hard ceramic material that can be scratched or roughened by traditional abrasives like pumice. Diamond polishing paste contains fine diamond particles, which are harder than porcelain, making it the ideal agent to effectively polish the surface to a high gloss without causing damage. Tin oxide is best for metallic restorations like gold or amalgam, and sodium bicarbonate is used in air polishing, which is not ideal for final polishing of ceramics.
Question 2: A dental hygienist is preparing to take a preliminary impression for study models. Which of the following materials is classified as an elastic, irreversible hydrocolloid commonly used for this purpose?
- Polyvinyl siloxane (PVS)
- Alginate (Correct answer)
- Polyether
- Impression compound
Correct answer: Alginate
Alginate is an elastic impression material classified as an irreversible hydrocolloid because it sets via a chemical reaction that cannot be reversed. It is widely used for preliminary impressions for study models, orthodontic appliances, and custom trays due to its ease of use, cost-effectiveness, and ability to capture detail in a moist environment. PVS and polyether are elastomers, and impression compound is a rigid, thermoplastic material.
Question 3: A dentist needs to place a temporary crown and requires a luting agent that has a sedative or palliative effect on the pulp. Which of the following cements would be the most suitable choice?
- Resin-modified glass ionomer (RMGI)
- Zinc phosphate
- Glass ionomer
- Zinc oxide-eugenol (ZOE) (Correct answer)
Correct answer: Zinc oxide-eugenol (ZOE)
Zinc oxide-eugenol (ZOE) cement is well-known for its sedative (obtundent) effect on the dental pulp, which is largely due to the eugenol component (oil of cloves). This property, combined with its low strength for easy removal, makes it an ideal choice for the temporary cementation of crowns and bridges. The other listed cements are designed for more permanent luting.
Question 4: A patient with a dental implant supporting a crown on tooth #8 presents for routine maintenance. To prevent damage to the implant surface, which type of instrument is contraindicated for calculus removal on the titanium abutment?
- Stainless steel curette (Correct answer)
- Graphite scaler
- Titanium-coated curette
- Resin or plastic scaler
Correct answer: Stainless steel curette
Stainless steel instruments are harder than the commercially pure titanium or titanium alloy used for dental implants. Using stainless steel scalers can scratch or gouge the implant surface, creating a niche for plaque and bacteria to accumulate, which can increase the risk of peri-implantitis. Instruments made of materials softer than or compatible with titanium, such as graphite, titanium, resin, or plastic, are recommended for implant maintenance.
Question 5: When placing a direct composite restoration, the material is typically applied and cured in 2mm increments. What is the primary reason for this incremental placement technique?
- To improve the final shade matching of the restoration.
- To reduce the effects of polymerization shrinkage. (Correct answer)
- To increase the radiopacity of the final restoration.
- To decrease the total time required for light curing.
Correct answer: To reduce the effects of polymerization shrinkage.
Composite resins shrink as they polymerize (harden) upon light curing, creating stress at the bond between the restoration and the tooth. Placing and curing the material in small increments (1-2mm) minimizes the overall shrinkage stress, reducing the risk of marginal gap formation, microleakage, cusp deformation, and post-operative sensitivity. While layering can aid in aesthetics, its primary purpose is to manage shrinkage stress.
Question 6: Which of the following dental materials is best known for its unique ability to release fluoride over time, providing a therapeutic, caries-inhibiting effect?
- Dental amalgam
- Composite resin
- Ceramic porcelain
- Glass ionomer cement (Correct answer)
Correct answer: Glass ionomer cement
Glass ionomer cements (GICs) are unique among restorative materials for their sustained fluoride release. This chemical property helps to inhibit secondary (recurrent) caries around restorations and can contribute to the remineralization of adjacent tooth structure. While some composites contain fluoride, GICs and resin-modified glass ionomers (RMGIs) release significantly more.
ADEX Dental Hygiene Dental Biomaterials Questions and Answers
A patient has a full gold crown on tooth #30 and a porcelain-fused-to-metal (PFM) crown on tooth #19.
Which polishing agent is most appropriate for the porcelain surface to achieve a high luster without causing abrasion?