This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
In direct pulp capping cases most important for the formation of dentinal bridges by dentinogenesis is: 
Select and explain. 
A. Calcium hydroxide and pulp interaction., B. Extracellular Matrix., C. De occlusion of involved teeth., D. Lack of pulpal inflammation.
A: Calcium hydroxide and pulp interaction.
Answer: A: Calcium hydroxide and pulp interaction. 
Explanation: Though there is no direct reference in book about dentinal bridge formation but bridge formation definitely occurs only after interaction between calcium hydroxide & cells of pulp tissue.