Which of the following is NOT an agent used to control hemostasis?

The correct choice is calcium carbonate because it is not primarily recognized as an agent for controlling hemostasis in surgical and dental procedures. Hemostasis refers to the processes that prevent and stop bleeding, and specific materials are utilized to aid in these processes effectively.

Oxidized regenerated cellulose, absorbable gelatin sponge, and microfibrillar collagen hemostat are all agents known for their roles in promoting blood clotting and controlling hemorrhage. They work by providing a scaffold for clot formation, promoting platelet aggregation, and allowing the natural clotting cascade to take place. These materials are engineered to interact with blood components and enhance the body's hemostatic responses when applied to wound sites.

In contrast, calcium carbonate's primary uses are in acid-neutralizing applications, such as in antacids, and it does not have the specific hemostatic properties exhibited by the other listed agents. Therefore, its absence from this list of hemostatic agents is appropriate, highlighting its lack of function in directly promoting or controlling bleeding during surgical interventions.