Which material would be used as a direct pulp cap on a pulpal exposure?

Calcium hydroxide is the preferred material for use as a direct pulp cap on a pulpal exposure due to its unique properties that promote the healing of dental pulp tissue. This material has a high pH, making it alkaline, which can help neutralize the acidic environment that may result from pulp exposure and encourages the formation of reparative dentin. Furthermore, calcium hydroxide exhibits antimicrobial properties, which helps to protect the exposed pulp from infection.

In addition to its biological compatibility, calcium hydroxide stimulates the pulp to respond and facilitate healing, thereby preserving vitality. When applied to an exposed pulp, it can provide a protective barrier and enhance the likelihood of successful pulp capping.

While other materials like zinc oxide eugenol and glass ionomer have their uses in dentistry, they do not possess the same level of pulp-dentin bridging capabilities and bioactivity that calcium hydroxide offers when it comes to direct pulp capping. Amalgam, primarily used as a restorative material, is not suitable for direct pulp caps since it lacks the necessary biological properties and could further irritate the pulp tissue if placed directly over an exposure.