D  

Direct pulp capping is indicated only when a small, vital pulp exposure is clean and uncontaminated. Success rates are high after mechanical or pinpoint exposures but drop sharply when the exposure is produced by caries, especially if the opening is large (>1 mm) because bacterial contamination makes healing unlikely [Al-Hiyasat 2006, PMID 17138715; Baume & Holz 1981, PMID 7030965].