Which of the following materials is the most ideal for
indirect pulp capping?
Calcium hydroxide remains the standard material for pulp capping of normal vital pulp tissue; it can possibly stimulate the repair reaction. A hard-setting calcium hydroxide capping material should be used. If the tooth is small (such as a first primary molar), hard-setting calcium hydroxide may also be used as the base for the restoration.  Some  studies  have  shown  successful  results  with direct capping of exposed pulps with adhesive bonding agents,  whereas  others  have  reported  pulpal  inflammation  and  unacceptable  results  with  this  technique.
McDONALD AND AVERY’S DENTISTRY  CHILD   ADOLESCENT 10thEd P:228
Calcium hydroxide
Zinc oxide eugenol cement
Zinc oxide powder only
Zinc oxyphosphate cement