Amalgam and Composite Restorations Flashcards

A patient requires a restoration on a posterior tooth with heavy occlusal forces. Which of the following materials is generally considered to have superior durability and longevity in such a high-stress area?

Answer: Amalgam

Amalgam has been used for over 150 years and is known for its exceptional strength and durability, making it a suitable choice for large cavities and restorations in posterior teeth that must withstand significant chewing forces. While composite resins have improved, amalgam often outperforms them in terms of longevity in high-stress situations.

When placing a composite restoration, what is the primary purpose of applying the material in small increments of 2mm or less?

Answer: To minimize polymerization shrinkage and associated stress on the tooth.

Composite resins shrink as they polymerize (harden) under the curing light. Placing the material in small increments (typically 2mm or less) and curing each layer individually helps to minimize the total shrinkage and reduces the stress placed on the bond between the tooth and the restoration. This technique helps prevent marginal gaps, microleakage, and postoperative sensitivity.

An EFDA is tasked with finishing and polishing a newly placed Class II amalgam restoration. Which of the following is a critical objective of this procedure?

Answer: To create a smooth, continuous margin that reduces plaque accumulation and prevents corrosion.

Finishing and polishing an amalgam restoration is crucial for its long-term success. The process removes surface irregularities and creates a smooth cavosurface margin. This smoothness helps to reduce plaque retention, minimizes the risk of recurrent decay at the margins, and makes the restoration less susceptible to tarnish and corrosion.

During the placement of a Class III composite on an anterior tooth, the EFDA notices that maintaining a dry field is extremely difficult due to gingival bleeding. What is the most likely consequence if moisture contaminates the preparation?

Answer: A significant decrease in bond strength, potentially leading to restoration failure.

Proper isolation and moisture control are critical for the success of composite restorations. Contamination of the etched enamel and dentin surfaces by saliva, blood, or moisture will interfere with the adhesive bonding process, resulting in a weak bond. This can lead to microleakage, postoperative sensitivity, and premature failure of the restoration.

Which of the following is a significant advantage of using composite resin for a restoration compared to amalgam?

Answer: It requires less removal of healthy tooth structure.

Composite restorations bond directly to the tooth structure, which allows for a more conservative tooth preparation. Unlike amalgam, which often requires the removal of healthy tooth structure to create mechanical retention (undercuts), composite preparations can be limited to just removing the decay. This preservation of natural tooth tissue is a major advantage.

An EFDA is assisting with a composite restoration. The dentist asks for the curing light. Which technique is considered best practice for light curing?

Answer: Positioning the light tip as close as possible and perpendicular to the composite surface.

To ensure adequate polymerization, the curing light tip should be positioned as close as possible to the composite material without touching it, and the light beam should be perpendicular to the surface being cured. This positioning maximizes the intensity of the light reaching the resin, ensuring a thorough cure. Angling the light or holding it too far away can lead to incomplete polymerization and a weaker restoration.