National Dental Assisting Examining Board (NDAEB) Practice Exam

What is the most common matrix system used for class II posterior restorations?

1. Matrix strip and rubber dam

2. Tofflemire retainer and matrix band

3. Clear plastic matrix

4. Sectional matrix system

The correct answer is: Tofflemire retainer and matrix band

The Tofflemire retainer and matrix band represent the most commonly used matrix system for class II posterior restorations due to their design and functionality. This system allows for the proper contouring of the restoration, which is critical in achieving the desired anatomical shape of posterior teeth. The Tofflemire retainer holds the matrix band securely in place, enabling the dentist to create a tight seal against the tooth structure while restoring interproximal contacts. The matrix band itself is typically made of stainless steel, which provides sufficient strength and stability during the placement of restorative materials such as amalgam or composite. This ensures that the material can be adequately packed against the existing tooth structure, minimizing the risk of voids and achieving a good fit for the restoration. Alternative systems, like clear plastic matrices and sectional matrix systems, have their benefits in specific scenarios but are less widely used for general class II restorations. For instance, a sectional matrix system is often utilized in areas where a precise, smaller restoration is needed, but it requires more technique sensitivity and may not provide the same level of ease and reliability afforded by the Tofflemire system in many clinical situations. The matrix strip and rubber dam, while applicable in some context, do not offer the same capabilities for