The response of four calcium hydroxides on monkey pulps.

Dentinal bridge formation and pulpal responses of four calcium hydroxide materials, pulp capping medicaments, MPC, Experimental MPC-12, Dycal and Pulpdent, were evaluated in primary and permanent monkey teeth. A total of 60 primary and 60 permanent teeth were used with each material placed in a Class V cavity exposure in Rhesus monkey teeth. The materials were placed on the exposed pulp tissue and were histologically evaluated at 3 days, 5 weeks and 8 weeks. After perfusion the teeth were processed using routine histological procedures. The 3-day pulpal responses in both primary and permanent teeth were moderate, characterized by disruption of the pulpal tissue directly beneath the exposure site and a zone of acute inflammation and hemorrhage in the underlying pulp. The 5-week response showed histological differences between the four medicaments, with Dycal producing the least amount of pulpal irritation with reparative dentin bridges occurring in 50% of the permanent teeth. Experimental MPC-12 stimulated one reparative dentin bridge, while Pulpdent and MPC showed no evidence of bridge formation. Pulpal responses to Dycal were moderate and moderate to severe for the other calcium hydroxide compounds. No reparative dentin bridges were seen in the primary teeth at 5 weeks with any of the materials, and the pulpal responses were of a moderate degree at that time. Eight-week responses were similar to the 5-week responses Dycal provoked a slight to moderate pulpal response with 50% success at bridging. Experimental MPC-12 initiated pulpal responses in the moderate to severe range with some bridging evident. Pulpdent incited moderate to severe histological responses with three teeth demonstrating bridge formation, and MPC provoked severe pulpal responses with no bridging. Primary teeth showed some bridging for all compounds except those treated with MPC, in which no evidence of bridging occurred, and moderate to severe pulpal responses were present.