Various matrix systems are available for use during tooth restoration to ensure that filling materials remain in the cavity during setting. Which one of the following types of matrix system is most likely to be used when placing a composite filling in a class III cavity?

In the context of placing a composite filling in a Class III cavity, the use of a plastic matrix system is most appropriate. A Class III cavity involves the proximal surfaces of anterior teeth, where access and visibility can be limited. The plastic matrix is designed to provide a supportive structure that helps to contain the composite material during the curing process.

Plastic matrices are flexible, allowing them to adapt closely to the tooth's contours, which is particularly useful for achieving a proper contact point with adjacent teeth. The transparency of plastic matrices also facilitates the curing process of the composite material, ensuring an even and thorough setting.

While other matrix systems have their specific applications, they may not offer the same level of effectiveness for Class III composites. For instance, the Tofflemire matrix is typically used for posterior teeth and larger restorations, whereas cervical foils and Sigveland matrices may not provide the necessary support and adaptability for anterior restorations. Thus, the choice of a plastic matrix aligns well with the requirements of restoring Class III cavities successfully.