Final answer:
A matrix is used to create a temporary wall for Class 2 tooth restoration which involves a proximal surface of a posterior tooth and may include the occlusal surfaces.
Step-by-step explanation:
A matrix must be used to create a temporary wall for Class 2 tooth restoration. When dealing with dental restorations, different classes define the location and extent of the decay or repair area. In particular, a Class 2 restoration involves a proximal surface of a posterior tooth, which may extend to include the occlusal surfaces. Proximal surfaces are the sides of the teeth that touch the adjacent teeth, which means there isn't a solid tooth structure to hold the filling material in place. Therefore, a matrix system is employed to simulate the missing wall or walls of the tooth structure for proper contouring and support of the dental material until it sets.