Calcium hydroxide is used as a direct pulp-capping material primarily because it:

Calcium hydroxide's strongly alkaline pH (about 12) is antibacterial and induces the pulp to form a reparative dentin bridge, protecting pulp vitality after exposure. MTA is a newer alternative with a better seal.Other options: It does not bond to enamel, its seal/solubility is a weakness (it can dissolve over time), and it is radiopaque enough to be seen; the therapeutic reason is its pH and dentin-bridge stimulation.Key exam takeaway: Ca(OH)2 caps pulps because its high pH is antibacterial and stimulates a reparative dentin bridge; MTA is a strong alternative.